RESULTS AND DISCUSSION

Transcription

1 RESULTS AND DISCUSSION 6.1 Reactive Species of Catalyst and Oxidant 6.2 Mechanism and Rate Law 6.3 Multiple Regression Analysis 6.4 Comparative Study 6.5 Conclusion 6.6 Future Prospect

2 In this chapter, an attempt has been made to discuss and analyze the experimentally observed kinetic data collected in the previous chapters. This chapter deals with kinetic investigations of Ru(III)/Ir(III) chloride catalyzed oxidation of reducing sugars (D-Glu, D-Fru, D-Ara & D-Mal) in acidic medium by NBP. In order to elucidate the mechanism for the above mentioned reactions, it is worthwhile to discuss the reactive species of various reactants i.e. reducing sugars (D-Glu, D-Fru, D-Ara & D-Mal), oxidant (NBP) and catalysts (Ru(III) chloride/ir(iii) chloride), in acidic medium. It has been observed that kinetic results obtained for the oxidation of various reducing sugars (D-Glu, D-Fru, D-Ara & D-Mal) in present thesis show dissimilar kinetic behavior. Thus, it is clear that mechanism for the oxidation of these reducing sugars (D-Glu, D- Fru, D-Ara & D-Mal) having different kinetic results will also be un-identical. The kinetic results obtained for them are summarized in the following way: Summary of kinetic results obtained in the oxidation of reducing sugars i.e. D- Glu, D-Fru, D-Ara and D-Mal by NBP in the presence of Ru(III) chloride The kinetic information based on our experimental findings are as follows:- 1. The title reaction exhibited first order dependence on oxidant i.e., NBP for all reducing sugars studied. 2. The reaction was found to be independent of the concentration of D-Glu, D- Fru, indicating zero order dependence on substrate concentration whereas D-Ara and D-Mal showed positive fractional order. 3. First order dependence of the rate on Ru(III) chloride observed in the oxidation of D-Glu, D-Ara and D-Mal whereas positive fractional order was reported in the oxidation of D-Fru. 4. During oxidation of D-Glu, reaction exhibited negative influence of [H + ] but showed positive influence during oxidation of D-Fru, D-Ara and D-Mal. 5. Negative effect of [Cl - ] was observed for the oxidation of D-Glu in the presence of Ru(III) catalyst while negative effect was observed for the oxidation of D-Fru, D-Ara, and D-Mal. 194

3 6. Change in ionic strength of the medium did not bring about any change in the rate of reaction. 7. The reaction rates were found to be enhanced significantly on increasing temperature. 8. Addition of mercuric acetate, Hg(OAc) 2 did not affect the rate of reaction in all the cases. 9. The rate of reaction decreased with decrease in dielectric constant of the medium for the oxidation of D-Ara while it had no significant effect on the rate, for the oxidation of D-Glu, D-Fru and D-Mal. 10. Addition of reduced product of oxidant i.e. NHP, showed negative effect on oxidation velocity of D-Fru but, it had negligible effect on the rate for the oxidation of D-Glu, D-Ara and D-Mal. Summary of kinetic results obtained in the oxidation of reducing sugars i.e. D- Glu, D-Fru, and D-Mal by NBP in the presence of Ir(III) chloride 1 The order with respect to [NBP] was found to exhibit first order for all reducing sugars. 2 The reaction was found to be independent of the concentration of substrates i.e. D-Glu, D-Fru and D-Mal indicating zero order dependence on substrate concentration. 3 First order dependence of the rate on Ir(III) chloride was observed in the oxidation of D-Fru, whereas positive fractional order was found in the oxidation of D-Glu and D-Mal. 4 In oxidation of D-Glu and D-Mal, reaction showed negative influence of [H + ] whereas in oxidation of D-Fru the same reaction showed positive influence. 5 Effect of potassium nitrate (ionic strength) for the oxidation of D-Glu, showed negative effect, whereas negligible effect was observed for the oxidation of D- Fru and D-Mal. 195

4 6 Effect of mercuric acetate for the oxidation of all reducing sugars, showed negligible effect on the rate of reaction. 7 In oxidation of D-Glu and D-Mal, reaction exhibited positive influence of [Cl - ] but showed negative influence during oxidation of D-Fru. 8 Addition of NHP did not affect the rate of oxidation of D-Glu and D-Fru but negatively influenced to oxidation of D-Mal. 9 The rate of reaction decreased with increase in dielectric constant of the medium for the oxidation of D-Glu and D-Fru while, it had no significant effect on the rate for the oxidation of D-Mal. 10 The reaction rates were found to be enhanced significantly on increasing the temperature. 6.1 REACTIVE SPECIES OF CATALYST AND OXIDANT In order to propose the mechanism for all the redox systems mentioned above, it is worthwhile to discuss the reactive species of various reactants including catalysts (Ru(III) and Ir(III) ) and oxidant (NBP) in acidic medium in the light of experimental data. Finally on the basis of these information s a suitable mechanism and rate law have been proposed which further support the kinetic observations. 6.1:01 Reactive Species of Ru(III) Chloride With the use of electrochemical and spectrophotometric techniques, the study for the chloro complexes of Ru(III) in 0.1 M KCl at ph 0.4, 1.0 and 2.0 at 25 0 C has been made by M.M. Taqui Khan and co-workers [Khan et al., 1986]. Their report showed that at the instant preparation of Ru(III) exists in solution in the ph range as four major species, i.e.[rucl 4 (H 2 O) 2 ] -, [RuCl 3 (H 2 O) 3 ], [RuCl 2 (H 2 O) 4 ] + and [RuCl(H 2 O) 5 ] 2+. Out of these four species, the species [RuCl 4 (H 2 O) 2 ] -, [RuCl 3 (H 2 O) 3 ], and [RuCl(H 2 O) 5 ] 2+ are reported to be fairly stable at ph 0.4, moderately stable at ph 1.0 and highly unstable at ph 2.0. It is also reported that the species [RuCl 2 (H 2 O) 4 ] + is stabilized in its hydrolyzed form, [RuCl 2 (H 2 O) 3 OH], according to the following equilibrium. 196

5 [RuCl 2 (H 2 O) 4 ] + + H 2 O [RuCl 2 (H 2 O) 3 OH] + H 3 O + (1) In the absence of any significant effect of [Cl - ] on the rate of oxidation, the hydrolyzed species, [RuCl 2 (H 2 O) 3 OH], can be taken as the reactive species Ru (III) chloride in acidic medium. But negligible effect of [Cl - ] on the rate of reaction rate is forced to assume that the above following equilibrium is in existence in the reaction under investigation. But in case of positive effect of [Cl - ] on the rate of reaction, we are forced to assume that the following equilibrium is in existence in the reaction under investigation. [RuCl + Cl - [RuCl 3 (H 2 O) 2 OH] - 2 (H 2 O) 3 OH] + H 2 O (2) Thus, when chloride ion positively influence the rate of reaction, [RuCl 3 (H 2 O) 2 OH] - can be assumed as the reactive species of Ru(III) chloride [Singh et al., 2009]. Electronic spectral studies by other workers [Cady et al., 1958; Connick et al., 1960 ] reveal that species such as [RuCl 5 (H 2 O)] 2-, [RuCl 4 (H 2 O) 2 ] -, [RuCl 3 (H 2 O) 3 ], [RuCl 2 (H 2 O) 4 ] + and [RuCl(H 2 O) 5 ] 2+ do not exist in an aqueous solution of RuCl 3. A study on the oxidation states of Ru has shown that Ru(III) exists, [Davfokratova, 1963; Griffith, 1967] in the acid medium as: RuCl 3.xH 2 O + 3HCl [RuCl 6 ] 3- + xh 2 O + 3H + (3) [RuCl [RuCl 5 (H 2 O)] 2-6 ] 3- + H 2 O + Cl - (4) The positive effect of the chloride ion suggests that the above equilibrium is favored towards the left [Cotton et al., 1988; Singh et al., 1980; Fine, 1960; Singh et al., 2002]. Several researchers [Singh et al., 1984; Singh et al., 1980] have employed the above equilibrium in Ru(III)-catalyzed oxidation of various substrates in acid medium. Based on the above discussion, [Ru(Cl) 3 (H 2 O) 2 OH] - has been selected as reactive species of Ru(III) for the oxidation of D-Glu, D-Fru. [RuCl 6 ] 3- and [Ru(Cl) 5 (H 2 O) 2 ] 2- have been selected as reactive species of Ru(III) for the oxidation of D-Ara and D- Mal, respectively. 197

6 6.1:02 Reactive species of Ir(III) chloride It is known that IrCl 3 in hydrochloric acid gives [IrCl 6 ] 3- reactive species [Day et al., 1986]. It has also been reported that Ir(III) and Ir(I) ions are the stable species of Ir [Chang et al., 1965]. Further according to Eq.(5) [IrCl 6 ] 3- gives [IrCl 5 H 2 O] 2-, [IrCl 4 (H 2 O) 2 ] - and [IrCl 3 (H 2 O) 3 ] species [Kravtsov et al., 1964; Poulsen et al., 1962; Domingos et al., 1969]. IrCl n-h 2 O [IrCl 6 -n (H 2 O)n] 3-n + Cl - (5) In case of positive effect of chloride on the rate of reaction, [IrCl 6 ] 3- has been considered to be the reactive species of Ir(III) chloride. But in the case negligible effect of chloride ion, [IrCl 5 (H 2 O)] 2- can be considered as the reactive species [Manibala et al., 1985]. Based on the above discussion, [Ir(Cl 6 )] 3- and [IrCl 5 (H 2 O)] 2- have been selected as reactive species of Ir(III) for the oxidation of D-Glu, D-Fru and D-Mal, respectively. 6.1:03 Reactive species of N-bromophthalimide It has been reported earlier by several workers [Das, 1984; Joshi et al., 2006; Singh et al., 2009, 2010], that NBP is good oxidizing and brominating agent because of large polarity of >N-Br bond. NBP, like other similar N-halo imides, may exist in various forms in acidic medium, i.e., free NBP, protonated NBP, Br +, HOBr, (H 2 OBr) +, as per the following equilibria: NBP + H 2 O HOBr + NHP (6) NBP + H + NHP + Br + (7) NBP + H + (NBPH) + (8) HOBr + H + (H 2 OBr) + (9) 198

7 If addition of phthalimide in the reaction mixture decreases the rate of oxidation in acidic medium, suggesting that pre-equilibria step involves a process in which phthalimide is one of the products and reactive species is HOBr. When NBP or (NBPH) + and cationic bromine (Br) + as reactive species of NBP is assumed as the reactive species, the derived rate laws should show negligible effect of phthalimide. When (H 2 OBr) + is taken as reactive species, the rate law obtained should show first order kinetics with respect to hydrogen ion concentrations. On the basis of above discussion and observed kinetic results, free NBP has been selected as reactive species of NBP in the Ru(III) catalyzed oxidation of D-Glu, D-Fru and D-Ara whereas NBPH + (i.e., protonated NBP) has been selected for D-Mal. Similarly, free NBP has been also selected as reactive species of NBP in Ir(III) catalyzed oxidation of D-Glu, D-Fru and HOBr has been selected for D-Mal. 6.1:04 Role of mercuric acetate (HgOAc) 2 It has been reported that Hg(II) can act as a homogeneous catalyst, co-catalyst or oxidant in reaction systems [Singh, 2004; Singh, 2009]. If the reaction rate is enhanced by the addition of Hg(OAc) 2, indicating the involvement of Hg(II) as co-catalyst in addition to its role as Br- ion scavenger [Venkatasubramanian et al., 1969; Bailar J C, 1956; Gopalkrishnan et al., 1980; Singh, 2003 ] In many systems it has also been found to show role of a scavenger [Singh 2010, 2010, 2009], a chemical agent that is added to a chemical mixture to counteract the effects of impurities. Therefore to ascertain the role of Hg(II) in the title reaction, its definite quantity had been added in each case. In order to ascertain the real role of Hg(OAc) 2, as a Br - scavenger, several experiments were performed with different initial concentrations of Hg(OAc) 2 with and without the presence of NBP under similar experimental conditions. The kinetic observations showed that the reaction rate was almost constant with the increases in concentration of Hg(OAc) 2, which negates its role as catalyst and a co-catalyst in the reaction mixture. Also, the reaction did not proceeds under similar conditions with Hg(OAc) 2 without using NBP; indicating Hg(OAc) 2 is not involved as an oxidant. Such kinetic observation suggest that Hg(OAc) 2 acted only as a Br - scavenger forming [HgBr]

8 6.2 MECHANISM AND RATE LAW Kinetic studies, coupled with other valuable techniques, provide one of the most satisfactory ways of obtaining the information about the mechanism and steps involved in the chemical reaction. Many difficult analytical problems have been also solved by the kinetic data. The mechanism of a reaction is detailed statements of the relative position of various atoms in a reacting system as the reactants get transformed into the products. The mechanism is elucidated on the basis of kinetic studies which require the determination of many kinetic and thermodynamic parameters, such as velocity, rate constant, order of reaction with respect to various reacting species, and influencing factor, specific reaction rate, stoichiometry of the reaction, kinetic and activation parameters, the study of the effect of catalyst, scavenger ionic strength etc. also play an important role in understanding the reaction mechanism. A number of reaction schemes for catalyzed reaction have been worked out in individual cases. A general mechanism for catalysed reaction [Laidler, 1991], where single substrate is involved is as follows: k 1 C + S X + Y (10) k -1 k X + W 2 P + Z (11) There are two possibilities which can be taken into existence with regard to the stability of intermediate complex X. In the first possibility, when k -1 is greater than k 2 then the intermediate complex X will be termed as Arrhenius complex. In the second possibility, when k 2 is greater than k -1 the intermediate complex X will be termed as Van't Hoff complex [Laidler, 1950]. 200

9 6.2:01 Reaction mechanism and rate law of D-Glu in the presence of Ru(III) On the basis of previous discussion and experimental data, a probable reaction mechanism has been proposed for the Ru(III) catalyzed oxidation of D-Glu in acidic medium(scheme 1). Here, the species C 2 is formed from the C 1 with the elimination of chloride ion and species C 1 and C 2 are in equilibrium having a constant K 1 (Eq. 12). The species C 2 reacts with NBP to give a complex C 3 with the elimination of proton having an equilibrium constant K 2 (Eq. 13). The negative entropy of activation in the oxidation of D-Glu by NBP supports above step. The species C 3 slowly decomposes to give the brominated species, [RuCl 2 (OBr) (H 2 O) 2 (OH)] (C 4 ) and phthalimide (NHP) (Eq. 14). The sum of steps results in the consumption of two molecules of NBP and one molecule of D-Glu. This is consistent with the observed stoichiometry of the oxidation of D-Glu by NBP. On the basis of reactions in scheme 1 and stoichiometric studies, the rate of disappearance of NBP can be expressed as [Singh et al., 2010] following way: Scheme-1 Reaction path for the oxidation of D-Glu by NBP in the presence of Ru(III) chloride [ RuCl 2 (H 2 O) 3 OH ] + (C 2 ) NBP K 2 - [ RuCl 2 (H 2 O) 2 (OH) 2 (NBP) ] (C 3 ) + H + (13) - [ RuCl 2 (H 2 O) 2 (OH) 2 (NBP) ] (C 3 ) k slow - [ Ru(OBr)Cl 2 (H 2 O) 2 OH ] + NHP (C 4 ) (14) H H - H 3 O + [ Ru(OBr)Cl 2 (H 2 O) 2 OH ] + S [ RuCl 2 (H 2 O) 3 (OH) ] + R C C OH (15) (C 4 ) OH OBr (C 5 ) R H C O H H c O OH Br O R-C-H + O H-C-OH (16) (C 5 ) 201

10 O NBP/H + R-C-H Ru(III) RCOOH (17) Where R stands for C 4 H 9 O 4 and S stands for D-Glu On the basis of reactions in Scheme 1 and stoichiometric studies, the rate of disappearance of NBP can be expressed as: Rate = k[c 3 ] (18) 2k k 2 K 1 [ Ru (III) ] [ NBP ] Rate = (19) k [ Cl - ] + k- 2 [H + ] [Cl - ] Eq. (19) is the rate law on the basis of observed kinetic orders with respect to each reactants of the reaction can very easily be explained. On reversing Eq. (19), we have Eq. (20) NBP rate = 1 k 1 = [Cl - ] 2k 2 K 1 [Ru(III)] + [Cl - ] [H + ] 2kK 1 K 2 [Ru(III)] (20) Eq. (20) indicates that if graph is plotted between NBP/Rate versus [H + ], [Cl - ] and 1/ [Ru(III)], a linear line with positive intercept on y-axis will be obtained (Fig. 6.1, 6.2 and 6.3). Such linearity in plots proved the validity of both the rate law and the proposed reaction scheme 1. From the values of intercepts and slopes of the plots, the values of k 2 K 1 and kk 1 K 2 were calculated as 5.26 x 10-5 mol dm -3 s -1 and 3.10 x 10-6 mol dm -3 s -1 respectively, for the oxidation of D-Glu. 202

11 NBP/Rate x 10-4 (sec) NBP/Rate x 10-4 (sec) [H + ] x 10 2 (mol dm -3 ) [Cl - ] x 10 5 (mol dm -3 ) Fig. 6.1: Plot between [H + ] versus NBP]/Rate for D-Glu Fig. 6.2: Plot between [Cl - ] versus [NBP]/Rate for D-Glu [NBP]/Rate x 10-4 (sec) /[Ru (III)] (mol -1 dm 3 ) Fig. 6.3: Plot between 1/[Ru(III)] versus [NBP]/Rate for D-Glu 203

12 6.2:02 Reaction mechanism and rate law of D-Fru in the presence of Ru(III) For the title reaction substrate D-Glu was found to show negligible effect therefore the reactive species of only catalyst and oxidant i.e., Ru(III) and NBP respectively are considered.. Based on previous experimental findings, the probable reaction mechanism is proposed The reaction between NBP and D-Fru in the acidic medium in the presence of Ru(III) has 1:2 stoichiometry of oxidant to reductant with first order dependence on [NBP] (Scheme 2). On the basis of positive fractional order of Ru(III) and [H + ] scheme 2 has been suggested. Here, the species C 2 is formed from the reaction of C 1 on hydrolysis with the liberation of Cl - and species C 1 and C 2 are in equilibrium having a constant K 1 i.e., Eq. (21). Protonated NBP (C 3 ) formed in Eq. (22) having a constant K 2. The species C 2 and C 3 react to give brominated species, [RuCl 2 (H 2 O) 3 HOBr] (C 4 ) and phthalimide (NHP) in Eq. (23). The species C 4 gives C 5 and proton in the rate determining step which is the slowest step i.e., Eq. (24). The species C 5 brominates the D-Fru molecule to form C 6 i.e. Eq. (25). The species C 6 forms C 4 H 9 O 4 COOH (arabinonic acid) and HCOOH (formic acid) as major products of the reaction in the fast steps Eq. (26) and (27).Overall, scheme 2 gives consumption of two molecules of NBP and per molecule of D-Fru, consistent with the observed stoichiometry. Scheme-2 Reaction path for the oxidation of D-Fru by NBP in the presence of Ru(III) chloride [RuCl 3 (H 2 O) 2 OH] - K 1 + H 2 O [RuCl + Cl - 2 (H 2 O) 3 OH] (21) (C 1 ) (C 2 ) K 2 NBPH + NBP + H + (C 3 ) (22) [RuCl 2 (H 2 O) 3 OH] + NBPH + (C 2 ) (C 3 ) K 3 [RuCl 2 (H 2 O) 3 HOBr] + NHP (23) (C 4 ) 204

13 [RuCl 2 (H 2 O) 3 HOBr] k [RuCl 2 (H 2 O) 3 OBr] + H + (C 4 ) (C 5 ) (24) OH H OBr O [RuCl 2 (H 2 O) 3 OBr] + R C C OH [RuCl 2 (H 2 O) 3 OH] + R C C H D-Fru OH (C 5 ) (C 6 ) (25) O Br O H + R C O H C H RCOOH Arabinonic acid + HCHO + HBr (26) (C 6 ) O H C H NBP/H + Ru(III) HCOOH Formic acid (27) Where R stands for C 4 H 9 O 4 On the basis of the scheme 2, the rate in terms of decrease in concentration of NBP can be expressed as: Rate = 2 k [ C 4 ] (28) On the basis of steps (21) to (27), Eqs. (29) - (38) can be obtained in the following forms, respectively: [ C 2 ] = K 1 [C 1 ] [Cl - ] (29) [ C 3 ] = K 2 [ NBP ] [ H + ] (30) [C 4 ] = K 3 [ C 3 ] [ C 2 ] [ NHP ] (31) On putting the value of [C 2 ] and [C 3 ] in Eq. (31) 205

14 [C 4 ] = K 1 K 2 K 3 [ NBP ] [ H + ] [ C 1 ] [ Cl - ]][ NHP ] (32) Substitution of Eq. (32) into Eq. (28) gives Rate = 2 k K 1 K 2 K 3 [NBP] [H + ] [C 1 ] [Cl - ] [NHP] (33) At any time of the reaction, the total concentration of NBP, i.e. [NBP] T can be shown as [ NBP ] T = [ NBP ] + [C 3 ] + [C 4 ] (34) On substituting the value of [C 3 ] & [C 4 ] in Eq. (34) we get Eq. (35) [NBP] T = [ NBP ] + K 2 [ NBP ] [ H + ] K 1 K 2 K 3 [ NBP ] [ H + ] [ C 1 ] + (35) [ Cl - ] [ NHP ] [ NBP ] = K 2 [ NBP ] T [ Cl - ] [ NHP ] [Cl - ] [ NHP ] [ H + ] + K 1 K 2 K 3 [ H + ] [ C 1 ] (36) Where [C 1 ] represents [Ru(III)], Therefore, 2 k K 1 K 2 K 3 [ NBP ] T [ Ru (III) ] [ H + ] Rate = [ Cl - ] [ NHP ] + K [ Cl - ] [ NHP ] [ H + 2 ] + K 1 K 2 K 3 [ H + ] [ Ru(III) ] (37) or Rate = 2 k K 1 K 2 K 3 [ NBP ] T [ Ru (III) ] [ H + ] [ Cl - ] [ NHP ] + K 1 K 2 K 3 [ H + ] [ Ru(III) ] (38) The rate expression obtained in equation (38) can be re-written as 206

15 [NBP] T Rate = [ Cl - ] [NHP] 2k K 1 K 2 K 3 [Ru(III)] [H + ] + 1 2k (39) Eq. (39), indicates that if graph is plotted between [NBP] T ]/rate and [Cl - ], 1/ [H + ], 1/[Ru(III)], [NHP], a straight line with an intercept on y-axis will be obtained (Fig. 6.4, 6.5, 6.6 and 6.7). The rate law (38) is in complete conformity with the observed data and the proposed reaction scheme. The value of k and K 1 K 2 K 3 calculated from the slope and intercept of the plot were 3.62 x 10-4 s -1, 4.49 x 10-3 mol dm -3 respectively. NBP/Rate x 10-4 (sec) [Cl - ] x 10 5 (mol dm -3 ) NBP/Rate x 10-4 (sec) /[H + ] (mol -1 dm 3 ) Fig. 6.4: Plot between [Cl - ] Fig. 6.5: Plot between 1/[H + ] versus [NBP]/Rate for D- Fru versus [NBP]/Rate for D- Fru 207

16 NBP / Rate x 10-4 (sec) NBP / Rate x 10-4 (sec) /[Ru(III)] (mol -1 dm 3 ) [NHP] x 10 4 (mol dm -3 ) Fig. 6.6: Plot between [Cl - ] versus [NBP]/Rate for D- Fru Fig. 6.7: Plot between [NHP] versus [NBP]/Rate for D- Fru 6.2:03 Reaction mechanism and rate law of D-Ara in the presence of Ru(III) On the basis of fractional order of D-Ara, considering the reactive species of Ru(III) chloride, reactive species of NBP and with the help of previous experimental findings, the probable reaction mechanism is proposed. Here, the species C 2 is formed from the reaction of C 1 on hydrolysis with the liberation of Cl - and species C 1 and C 2 are in equilibrium having a constant K 1 in Eq. (40). Protonated NBP (C 3 ) is formed in Eq. (41) having a constant K 2. Then C 2 react with sugar molecule (D-Ara) to form C 4 having a constant K 3 i.e., Eq. (42). In Eq. (43) C 3 and C 4 reacts and form C 5 having a constant K 4. The species C 5 gives products on hydrolysis. Overall, Scheme 3 suggested 1 mole of D-Ara is oxidized by 2 moles of NBP. The following reaction scheme has been suggested on the basis of kinetic results: Scheme-3 Reaction path for the oxidation of D-Ara by NBP in the presence of Ru(III) chloride [RuCl 6 ] 3- + H 2 O K 1 [RuCl 5 (H 2 O)] 2- + Cl - (C 1 ) (C 2 ) (40) 208

17 K 2 NBP + H + [NBPH + ] (C 3 ) (41) [RuCl 5 (H 2 O)] 2- + C 5 H 10 O 5 K 3 [RuCl 5 C 5 H 10 O 5 ] 2- + H 2 O (42) (C 2 ) (C 4 ) [RuCl 5 C 5 H 10 O 5 ] 2- (C 4 ) + [NBPH + ] (C 3 ) K 4 [RuCl 5 (NBPH)C 5 H 10 O 5 ] - (43) (C 5 ) [RuCl 5 (NBPH)C 5 H 10 O 5 ] - + H k [RuCl 5 (H 2 O)] - 2 O + NHP + H + + HO (C 5 ) OH O (C 6 ) OBr OH (44) OH HO O (C 6 ) OBr OH C 5 H 9 COOH Erythronic acid + Br - (45) HCHO NBP/H + Ru(III) HCOOH Formic acid (46) On the basis of the reaction scheme 3, the rate in terms of decrease in concentration of NBP can be expressed as: Rate = 2k [C 5 ] (47) [C 2 ] = K 1 [C 1 ] [Cl - ] (48) [C 3 ] = K 2 [NBP] [H + ] (49) [C 4 ] = K 3 [C 2 ] [D-Ara] (50) Putting the value of [C 2 ] in above equation, we have 209

18 [C 4 ] = K 1K 3 [C 1 ] [D-Ara] [Cl - ] (51) [C 5 ] = K 4 [C 3 ] [C 4 ] (52) Putting the value of [C 3 ] and [C 4 ] in above Eq., we get Eq. (53) [C 5 ] = K 1 K 2 K 3 K 4 [C 1 ] [D-Ara] [NBP] [H + ] [Cl - ] (53) Substitution of Eq. (53) into Eq. (47) gives [C 5 ] = 2 k K 1 K 2 K 3 K 4 [C 1 ] [D-Ara] [NBP] [H + ] [Cl - ] (54) At any time of the reaction, the total concentration of NBP, i.e. [NBP] T can be shown as: [ NBP ] T = [ NBP ] + [C 3 ] + [C 5 ] (55) On substituting the value of [C 3 ] & [C 5 ] in Eq. (55) we get Eq. (56) [NBP] T = NBP + K 2 [NBP] [H + ] + K 1 K 2 K 3 K 4 [C 1 ] [D-Ara] [NBP] [H + ] [Cl - ] (56) [NBP] = [NBP] T [Cl - ] [Cl - ] + K 2 [Cl - ] [H + ] + K 1 K 2 K 3 K 4 [C 1 ] [D-Ara] [H + ] (57) Rate = 2k K 1 K 2 K 3 K 4 [C 1 ] [D-Ara] [NBP] T [H + ] [Cl - ] + K 2 [Cl - ] [H + ] + K 1 K 2 K 3 K 4 [C 1 ] [D-Ara] [H + ] (58) Where [C 1 ] represents [Ru(III)] At any time of the reaction, the total concentration of [Ru(III)], i.e. [Ru(III)] T can be shown as 210

19 [Ru(III)] T = [C 1 ] + [C 2 ] + [C 4 ] + [C 5 ] (59) Putting the value of [C 1 ], [C 2 ], [C 4 ] and [C 5 ] in above Eq. (59), we have [Ru(III)] T = [C 1 ] + K 1 [C 1 ] [Cl - ] + K 1 K 3 [C 1 ] [D-Ara] [Cl - ] + K 1 K 2 K 3 K 4 [C 1 ][D-Ara][NBP][H + ] [Cl - ] (60) [C 1 ] = [Ru(III)] [Cl - ] [Cl - ] + K 1 + K 1 K 3 [D-Ara] + K 1 K 2 K 3 K 4 [NBP] [H + ] (61) From Eq. (48) to (61) we can finally obtain Eq. (62), which is the rate law on the basis of which observed kinetic orders with respect to each reactant can easily be explained. Rate = 2kK 1 K 2 K 3 K 4 [NBP] T [H + ] [D-Ara] [Ru(III) T ] [Cl - ] K 1 + K 1 K 3 [D-Ara] + K 2 [H + ] [Cl - ] (62) The rate expression obtained in Eq. (62) can be re-written as 1 k 1 = [NBP] T Rate = [Cl - ] + 2k K 1 K 2 K 3 K 4 [H + ] [D-Ara] [Ru(III)] T 1 + 2k K 2 K 3 K 4 [H + ] [D-Ara] [Ru(III)] T 1 + 2kK 2 K 4 [H + ] [Ru(III)] T [Cl - ] (63) 2kK 1 K 3 K 4 [D-Ara] [Ru(III)] T According to Eq. (63), graph is plotted 1/ rate versus [Cl - ], 1/[H + ], 1/[Ru(III)], and 1/[D-Ara] should be straight line having an intercept on the y-axis (Fig 6.8, 6.9, 6.10 and 6.11). The value of kk 1 K 2 K 3 K 4, kk 2 K 3 K 4, kk 2 K 4 and kk 1 K 3 K 4 calculated from the slope and intercept of the plot were1.08 x 10 2 mol -1 dm 3, 3.57 x 10-1 mol -1 dm 3, 7.71 x 10 3 mol -1 dm 3 and 6.25 x 10 6 mol -1 dm 3 respectively. 211

20 NBP/Rate x 10-4 (sec) NBP/Rate x 10-4 (sec) [Cl - ] x 10 5 (mol dm -3 ) / [H + ] (mol -1 dm 3 ) Fig. 6.8: Plot between [Cl - ] versus Fig. 6.9: Plot between 1/[H + ] [NBP]/Rate for D- Ara versus [NBP]/Rate for D- Ara NBP / Rate x 10-4 (sec) NBP / Rate x 10-4 (sec) /[Ru(III)] (mol -1 dm 3 ) / [D-Ara] (mol -1 dm 3 ) Fig. 6.10: Plot between 1/[Ru(III)] versus [NBP]/Rate for D-Ara Fig. 6.11: Plot between 1/[D-Ara] versus [NBP]/Rate for D-Ara 212

21 6.2:04Reaction mechanism and rate law of D-Mal in the presence of Ru(III) On the basis of kinetic results of D-Mal, reported in previous section and taking into consideration the reactive species of Ru(III) chloride and NBP, the following reaction scheme has been suggested. Here, NBP and proton react to formed protonated NBP having an equilibrium constant K 1 in Eq. (64). C 1 react with chloride ion which is positively influenced on the rate of title reaction, to formed C 2 having an equilibrium constant K 2. This is clear in Eq. (65). Then C 2 react with sugar moiety (D-Mal) in Eq. (66) to formed C 3 having an equilibrium constant K 3. The species C 4 is formed when the C 3 react with protonated NBP having an equilibrium constant K 4 in Eq. (66). The species C 4 gives [RuCl 6 ] 3-, phthalimide and species C 5 in the rate determining step which is the slowest step i.e., Eq. (68). The species C 5 forms products i.e., formic acid and arabinonic acid, which is clear in Eq. (69) to Eq. (71). Scheme 4 suggested 1 mole of D-Mal is oxidized by 2 moles of NBP. The following reaction scheme has been suggested on the basis of kinetic results: Scheme-4 Reaction path for the oxidation of D-Mal by NBP in the presence of Ru(III) chloride K 1 NBP + H + [NBPH + ] (64) K 2 [RuCl 5 (H 2 O)] 2- + [Cl - ] [RuCl 6 ] 3- + H 2 O (65) (C 1 ) (C 2 ) K 3 [RuCl 6 ] 3- + S [RuCl 6 (S)] 3- (C 2 ) (C 3 ) (66) [RuCl 6 (S)] 3- + [ NBPH + ] [RuCl 6 (NBPH)S] 2- K 4 (67) (C 3 ) (C 4 ) 213

22 OH OH k [RuCl 6 (NBPH)S] 2- + H [RuCl 6 ] 3-2 O + NHP + R CH CH4+ H + slow and rate (C 4 ) determining step (C 5 ) OBr (68) OH OH R CH CH fast HCOOH + RCHO + HBr (69) ( C 5 ) OBr Formic acid RCHO OH NBP/Ir(III) H + R C H OBr (70) OH R C H fast R C OH + HBr (71) OBr O Arabinonic acid Where, R = C 4 H 9 O 4 On the basis of the reaction scheme 4, the rate in terms of decrease in concentration of NBP can be expressed as: Rate = k[c 4 ] (72) On the basis of Eq. (64) to (71), Eq. (73) and (74) can be obtained. [C 2 ] = K 2 [C 1 ][Cl - ] (73) [C 4 ] = K 4 [C 3 ][NBPH + ] (74) or [C 3 ] = K 3 [C 2 ][S] (75) From the Eq. (74) and (75), we get [C 4 ] = K 4 [NBPH + ] K 3 [C 2 ][S] (76) From the Eq. (73) and (76), we get Eq. (77) 214

23 [C 4 ] = K 3 K 4 K 1 [NBP][H + ]K 2 [C 1 ][Cl - ][S] (77) From the Eq. (72) and (77), we have Rate = kk 1 K 3 K 4 [NBP][H + ][C 1 ][Cl - ][S] (78) At any time of the reaction, the total concentration of NBP, i.e. [NBP] T can be shown as [NBP] T = [NBP] + [NBPH + ] + [C 4 ] (79) or [NBP] T = [NBP] 1 + K 1 [H + ]+K 1 K 2 K 3 K 4 [S][H + ][Cl - ][C 1 ] (80) or [NBP] = [NBP] T 1 + K 1 [H + ]+K 1 K 2 K 3 K 4 [S][H + ][Cl - ][C 1 ] (81) At any time of the reaction, the total concentration of [Ru(III)], i.e. [Ru(III)] T can be shown as [Ru(III)] T = [C 1 ] + [C 2 ] + [C 3 ] + [C 4 ] (82) On substituting the values of [C 2 ] [C 3 ] and [C 4 ] in Eq. (82), we get Eq. (83) [Ru(III)] T = [C 1 ] + K 2 [C 1 ][Cl - ] + K 3 [C 2 ][S] + K 1 K 2 K 3 K 4 [NBP][H + ][S][Cl - ][C 1 ] (83) or [C 1 ] = or [Ru(III)] T 1 + K 2 [Cl - ]+ K 2 K 3 [Cl - ][S] + K 1 K 2 K 3 K 4 [NBP][H + ][S][Cl - ] (84) [C 1 ] = [Ru(III)] T 1 + K 2 [Cl - ]+ K 2 K 3 [Cl - ][S] (85) From Eq. (78) and (85), we can finally obtain Eq. (86), which is the rate law. 215

24 Rate = kk 1 K 2 K 3 K 4 [H + ][Cl - ][S][NBP] T [Ru(III)] T 1 + K 1 [H + ]+ K 2 [Cl - ]+K 1 K 2 K 3 [H + ][Cl - ][S] (86) The rate expression obtained in equation (86) can be re-written as Rate = [NBP] T 1 k 1 = 1 2kK 1 K 2 K 3 K 4 [H + ][Cl - ][S][Ru(III)] T + 1 2kK 2 K 3 K 4 [Cl - ][S][Ru(III)] T + 1 2kK 1 K 3 K 4 [H + ][S][Ru(III)] T + 1 2kK 4 [Ru(III)] T (87) Where, [C 1 ] stands for [Ru(III)] and S stands for [D-Mal] According to Eq. (87), graph is plotted 1/ rate versus 1/[Cl - ], 1/[H + ], 1/[Ru(III)] and 1/[D-Mal] should be straight line having an intercept on the y-axis (Fig 6.12, 6.13, 6.14, 6.15). The value of kk 1 K 2 K 3 K 4, kk 2 K 3 K 4, kk 1 K 3 K 4 and kk 4 calculated from the slope and intercept of the plot were1.17 x mol -1 dm 3, 0.19 x mol -1 dm 3, 1.17 x 10 7 mol -1 dm 3 and 7.59 x 10-1 mol -1 dm 3 respectively. NBP/Rate x 10-4 (sec) / [Cl - ] (mol -1 dm 3 ) NBP/Rate x 10-4 (sec) / [H + ] (mol -1 dm 3 ) Fig. 6.12: Plot between 1/[Cl - ] Fig. 6.13: Plot between 1/[H + ] versus [NBP]/Rate for D- Mal versus [NBP]/Rate for D- Mal 216

25 1.6 NBP/Rate x 10-4 (sec) NBP/Rate x 10-4 (sec) / [Ru(III)] (mol -1 dm 3 ) / [D-Mal] (mol -1 dm 3 ) Fig. 6.14: Plot between 1/[Ru(III)] versus [NBP]/Rate for D- Mal Fig. 6.15: Plot between 1/[D-Mal] versus [NBP]/Rate for D- Mal 6.2:05 Reaction mechanism and rate law of D-Glu in the presence of Ir(III) For the title reaction substrate D-Glu was found to show negligible effect therefore the reactive species of only catalyst and oxidant i.e., Ir(III) and NBP respectively are considered. Based on previous experimental findings, the probable reaction mechanism is proposed. Here, the species C 2 is formed from the reaction of C 1 and chloride ion having an equilibrium constant K 1 in Eq. (88). The species C 2 react with NBP to C 3 in Eq. (89) having a constant K 2. Then the species C 3 gives C 4 and phthalimide in the rate determining step which is the slowest step i.e., Eq. (90). The species C 4 react with C 5 which gives products. Overall, scheme 5 suggested 1 mole of D-Glu is oxidized by 2 moles of NBP in the following way: 217

26 Scheme-5 Reaction path for the oxidation of D-Glu by NBP in the presence of Ir(III) chloride [IrCl 2 (H 2 O) 3 OH] + Cl - K 1 [IrCl 3 (H 2 O) 2 (OH)] - + H 2 O (88) (C 1 ) (C 2 ) [IrCl 3 (H 2 O) 2 (OH)] - K 2 + NBP [IrCl 3 (NBP)(H 2 O)(OH) 2 ] 2- -H 2 O (C 2 ) (C 3 ) + H + (89) [IrCl 3 (NBP)(H 2 O)(OH) 2 ] 2- (C 3 ) k slow [IrCl 3 (OBr)(H 2 O)(OH)] 2- + (C 3 ) NHP (90) [IrCl 3 (OBr)(H 2 O)(OH)] 2- + D-Glu [IrCl 3 (OBr)(D-Glu)OH] 2- + H 2 O (91) (C 4 ) (C 5 ) [IrCl 3 (OBr)(D-Glu)OH] H 2 O (C 5 ) [IrCl 2 (H 2 O) 3 OH] - + Cl - + O - H H O HO HO H OH H (C 6 ) H OBr ( 92 ) O - H H O HO HO H OH H (C 6 ) H OBr HO HO H OH H O H OH H O D-glucono-1,5-lactone (93) On the basis of all the steps of Scheme -5, the rate in terms of decrease in concentration of NBP can be expressed as: Rate = 2k [C 3 ] (95) 218

27 On the basis of equilibrium steps (87) to (94), Eq. (96) (98) can be obtained in the following way: [C 3 ] = K 2 [C 2 ] [NBP] [H + ] (96) [C 3 ] = 2kK 1 K 2 [C 1 ] [NBP] [H + ] (97) At any moment in the reaction, the total concentration of [NBP], i.e. [NBP] T can be shown as: [NBP] = T [NBP] + [C 3 ] (98) On substituting the value of [C 3 ] from Eq. (98), we get Eq. (99) [NBP] = [NBP] [H + T ] [H + ] + K 1 K 2 [C 1 ] [Cl - ] (99) From Eq. (95), (96) and (99) we get Eq. (100) Rate 2k K 1 K 2 [C 1 ] [Cl - ][NBP] T [H + ] + K 1 K 2 [C 1 ] [Cl - ] (100) Where, [ C 1 ] = [Ir(III)] So, Eq. (100) can be written as: Rate 2k K 1 K 2 [Ir(III)] [NBP] [Cl - ] [H + ] + K 1 K 2 [Ir(III)] [Cl - ] (101) : Eq. (101) is the rate law on the basis of which observed kinetic orders with respect to each reactants of the reaction can very easily explained. Eq. (100) can be written as: [NBP] Rate [H + ] 2k K 1 K 2 [Ir(III)] [Cl - ] + 1 2k (102) 219

28 According to Eq. (102), if graph is plotted between [NBP]/rate versus [H + ], 1/[Cl - ], 1/[Ir(III), a straight line having an intercept on y-axis will be obtained (Fig. 6.16, 6.17 and 6.18). This proves the validity of the rate law (101) and hence the proposed reaction scheme 1. From the slope and intercept of the straight line, the values of k and K 1 K 2 have been calculated and found to be 2.15 x 10-4 s -1, 8.30 x 10 8 mol -1 dm 3 respectively NBP/Rate x 10-4 (sec) NBP/Rate x 10-4 (sec) [H + ] x 10 2 (mol -1 dm 3 ) 10-3 / [Cl - ] (mol -1 dm 3 ) Fig : Plot between [H + ] Fig : Plot between 1/[Cl - ] versus [NBP]/Rate for D- Glu versus [NBP]/Rate for D- Glu 220

29 NBP/Rate x 10-5 (sec) / [Ir(III)] (mol -1 dm 3 ) Fig Plot between 1/[Ir(III)] versus [NBP]/Rate for D- Glu 6.2:06 Reaction mechanism and rate law of D-Fru in the presence of Ir(III) In view of negative effect of chloride ion, negligible effect of NHP and D-Fru on the rate of reaction, [IrCl 6 ] - and free NBP have been assumed to be reactive species of iridium (III) chloride and NBP respectively. In the scheme (6), the species C 2 is formed from the reaction of C 1 with the water molecule and species C 1 and C 2 are in equilibrium having a constant K 1 in Eq. (103). In second step, NBP react with H + and form protonated NBP i.e. C 3 in equilibrium having also a constant K 2 i.e., Eq. (104). The species C 2 reacts with C 3 to give a species C 4 having an equilibrium constant K 3 with the liberation of proton in the Eq. (105). The species C 4 slowly decomposes to give brominated species, [IrCl 5 (OBr)] 3- (C 5 ) and phthalimide (NHP) (Eq. 106). The species C 5 brominates the D-Fru molecule to form C 5 (intermediate species). The intermediate species C 5 brominates the D-Fru molecule to form C 6 (Eq. 107). The species C 6 forms C 4 H 9 O 4 COOH (arabinonic acid and HCOOH (formic acid) as major products of the reaction by fast steps (Eq.108 and 109). The following reaction scheme has been suggested on the basis of kinetic results: 221

30 Scheme-6 Reaction path for the oxidation of D-Fru by NBP in the presence of Ir(III) chloride K [ IrCl 6 ] H 2 O [ IrCl 5 (H 2 O)] 2- + Cl - (C 1 ) (C 2 ) (103) K 2 NBP + H + [ NBPH+ ] (104) (C 3 ) [ IrCl 5 (H 2 O)] 2- + [ NBPH + ] K 3 [ IrCl 5 (OH)NBP] H + (105) (C 2 ) (C 3 ) (C 4 ) [IrCl 5 (OH)NBP] 2- k NHP + [IrCl 5 OBr] 3- (C 4 ) (C 5 ) (106) OH H OBr O [IrCl 5 OBr] 3- + R C C OH [IrCl 5 OH] + R C C H (C 5 ) D-Fru OH (C 6 ) (107) O Br O R C O H C H (C 6 ) H + RCOOH + HCHO + HBr (108) Arabinonic acid O H C H NBP/H + Ir(III) HCOOH Formic Acid (109) Where. R = C 4 H 9 O 4 222

31 On the basis of all the steps of scheme-6, the rate in terms of decrease in concentration of NBP can be expressed as: Rate = 2k [C 4 ] (110) On the basis of steps (103) to (109), Eqs. (111) - (122) can be obtained in the following forms, respectively: [C 2 ] = K 1 [C 1 ] Cl - ] (111) [C 3 ] = K 2 [NBP] [H + ] (112) [C 4 ] = K 3 [C 2 ][C 3 ] (113) With the help Eq. (111 to 113), we can write Eq. (114) as [C 4 ] = K 1 K 2 K 3 [C 1 ][NBP][H + ] [Cl-] (114) At any moment of the reaction, the total concentration of [NBP], i.e. [NBP] T can be represented as [NBP] T = [NBP] + [C 3 ] + [C 4 ] (115) With the help of Eq. (110, 112, 114 and 115) we can write Eq. (116) as Rate = 2k K 1 K 2 K 3 [C 1 ] [H + ] [NBP] T [Cl - ] + K 2 [H + ] [Cl - ] + K 1 K 2 K 3 [C 1 ] [H + ] (116) Eq. (116) is the rate law on the basis of which observed kinetic orders with respect to each reactants of the reaction can very easily explained. Eq. (116) can be written as: 223

32 Rate [NBP] T = 2k K 1 K 2 K 3 [C 1 ][H + ] [Cl - ] + K 2 [H + ] [Cl - ] + K 1 K 2 K 3 [C 1 ] [H + ] (117) The rate expression obtained in equation (117) can be re-written as [NBP] T Rate = 1 = k 1 [Cl - ] [Cl - ] 2k K 1 K 2 K 3 [C 1 ][H + ] + 2kK 1 K 3 [C 1 ] k (118) According to equation (118), if graph is plotted between [NBP]/rate versus 1/[H + ], [Cl - ], and 1/[Ir(III)], a straight line having an intercept on y-axis will be obtained (Fig. 6.19, 6.20 and 6.21). This proves the validity of the rate law (117) and hence the proposed reaction scheme 6. From the slope and intercept of the straight lines, the values of k, K 1 K 2 K 3 and K 1 K 3 have been calculated and found to be 1.03 x 10-3 s -1, 1.85 x 10 1 mol -1 dm 3 and 1.64 x10-1 respectively NBP/Rate x 10-4 (sec) NBP/Rate x 10-4 (sec) / [H + ] (mol -1 dm 3 ) [Cl - ] x 10 5 (mol dm 3 ) Fig. 6.19: Plot between 1/[H + ] versus [NBP]/Rate for D- Fru Fig. 6.20: Plot between [Cl - ] versus [NBP]/Rate for D- Fru 224

33 NBP/Rate x 10-4 (sec) / [ Ir(III)] (mol -1 dm 3 ) Fig. 6.21: Plot between 1/[Ir(III)] versus [NBP]/Rate for D- Fru 6.2:07Reaction mechanism and rate law of D-Mal in the presence of Ir(III) On the basis of nature of substrate (D-Mal), reactive species of Ir(III) chloride and the observed kinetic results, the following reaction steps are suggested. Here, in the Eq. (119), NBP gives HOBr and NHP having an equilibrium constant K 1. The species C 2 react with chloride ion to form the new species C 3 having a constant K 2 in Eq. (120). Then the species C 3 react with C 1 to gives a complex C 4 and proton having a constant K 3 i.e., Eq.(121). The species C 4 gives a species C 5 with the liberation of chloride ion in the Eq. (122) which is slow and rate determining step. The species C 5 react with substrate (D-Mal) and formed C 6 in Eq. (123).The species C 5 forms C 4 H 9 O 4 COOH (arabinonic acid and HCOOH (formic acid) as major products of the reaction by fast steps (Eq.124 and 125). The following reaction scheme has been suggested on the basis of kinetic results: Scheme-7 Reaction path for the oxidation of D-Mal by NBP in the presence of Ir(III) chloride NBP + H 2 O HOBr + NHP K 1 (119) (C 1 ) 225

34 [IrCl 5 (H 2 O)] 2- + Cl - K 2 [IrCl 6 ] 3- + H 2 O (120) (C 2 ) (C 3 ) K 3 [IrCl 6 ] 3- + HOBr [IrCl 6 OBr] 4- + H + (121) (C 3 ) (C 1 ) (C 4 ) k [IrCl 6 OBr] 4- [IrCl 5 OBr] 3- + Cl H - 2 O (C 4 ) (C 5 ) (122) OH OH [IrCl 5 OBr] 3- + S + H 2 O [IrCl 5 OH] + R CH CH (C 5 ) (C 6 ) OBr (123) OH OH R CH CH (C 6 ) OBr fast HCOOH + RCHO Formic acid + HBr (124) OH R C H R C OH + HBr (125) OBr O Arabinonic acid Where, R stands for C 4 H 9 O 4 and S stands for sugar i.e., D-Mal On the basis of the mechanism in scheme 7, the rate in term of decrease in concentration of NBP can be expressed as: Rate = 2k[C 3 ] (126) On the basis of equilibrium steps (119) to (125), Eq. (127) to (133) can be obtained in the following forms, respectively: 226

35 K 1 = [HOBr] = [HOBr] [NHP] [NBP] K 1 [NBP] [NHP] (127) (128) [C 2 ] = K 2 [Cl - ] [C 1 ] ( 129) K 3 = K 3 = [C 3 ] [H + ] [C 2 ] [HOBr] - [ C 3 ] [H + ] [NHP] [C 2 ] K 1 [NBP] (130) (131) [C 3 ] K 1 K 3 [C 2 ] [NBP] = (132) [H + ] [NHP] [C 3 ] = K 1 K 2 K 3 [NBP] [C 1 ][Cl - ] (133) [NHP] [H + ] At any moment of the reaction, the total concentration of [NBP], i.e. [NBP] T can be represented as [NBP] T = [NBP] + [HOBr] + [C 3 ] (134) Substituting the values of [HOBr] and [C 3 ] in Eq. (134), we get K 1 [NBP] K 1 K 2 K 3 [NBP] [C 1 ] [Cl - ] = [NBP] + + (135) [NBP] T [NBP] [NHP] [H + ] [NBP] = [NBP] T [H + ] [NHP] [H + ] [NHP] + K 1 [H + ] + K 1 K 2 K 3 [C1][Cl - ] (136) From Eq. (126), (133) and (135) we get Eq. (137) 227

36 Rate = 2k K 1 K 2 K 3 [C 1 ] [Cl - ] [NBP] T [H + ] [NHP] + K 1 [H + ] + K 1 K 2 K 3 [C 1 ][Cl - ] (137) The rate expression obtained in equation (117) can be re-written as [NBP] T Rate = 1 [H + ] [NHP] [H + ] = + + k 1 2kK 1 K 2 K 3 [C 1 ] [Cl-] 2kK 2 K 3 [C 1 ] [Cl - ] 1 2k (138) Where, [C 1 ] stands for [Ir(III)] According to equation (138), if a graph is plotted between [NBP] T /rate versus [H + ], 1/ [Cl - ], 1/ [Ir(III)] and [NHP], a straight line having an intercept on y-axis will be obtained (Fig. 6.22, 6.23, 6.24 and 6.25). This proves the validity of the rate law (137) and hence the proposed reaction scheme 7. From the slope and intercept of the straight lines, the values of k, K 1 K 2 K 3 and K 2 K 3 have been calculated and found to be 5.06 x 10-4 s -1, 2.20 x 10 4 mol -1 dm 3 and 5.67 x10 7 mol -1 dm 3 respectively. 0.7 NBP/Rate x 10-4 (sec) NBP/Rate x 10-4 (sec) [H + ] x 10 2 (mol dm 3 ) / [Cl - ] (mol -1 dm 3 ) Fig. 6.22: Plot between [H + ] versus Fig. 6.23: Plot between 1/[Cl - ] versus 228

37 [NBP]/Rate for D- Mal [NBP]/Rate for D- Mal NBP/Rate x 10-4 (sec) NBP/Rate x 10-4 (sec) / [Ir(III)] (mol -1 dm 3 ) [NHP] x 10 4 (mol dm 3 ) Fig. 6.25: Plot between 1/[Ir(III)] versus [NBP]/Rate Fig. 6.23: Plot between [NHP] versus [NBP]/Rate for D- Mal 6.2:08 Oxidation products in Ru(III)/ Ir(III) catalyzed oxidation of D-Glu, D-Fru, D-Ara and D-Mal by NBP in acidic medium The product analysis is strong evidence to the proposed reaction mechanism. Various sets of reactions were carried out with different [NBP]:[Reducing Sugars] ratios under the conditions of [NBP] >> [Reducing Sugars]. Estimation of unconsumed NBP indicates that two moles of NBP were required to oxidize one mole of reducing Sugars in the present of requisite amount of all reactant. O O C C Ru(III)/Ir(III) Reducing Sugars + 2 N Br + H 2 O Products +2 N H + 2HBr (139) C and H + C O O NBP NHP In Eq. (139) the main reaction products of the oxidation of D-Glu in the presence 229

38 of Ru(III) chloride was identified as arabinonic acid and formic acid i.e., Eq. (140). The oxidation product was identified by GCMS (Fig. 6.26) and by TLC, spot test [Feigl, 1966; Vogel, 1958] method [Singh et al. 2010]. C 6 H 12 O C 8 H 4 O 2 NBr + 2H 2 O RCOOH + HCOOH + 2C 8 H 4 O 2 NH + 2HBr (140) Where, R=C 4 H 9 O 4 Arabinonic Acid In Eq. (139) the main reaction products of the oxidation of D-Fru in the presence of both catalysts Ru(III) and Ir(III) chloride was identified as arabinonic acid and formic acid. The oxidation product was identified by TLC and by spot test method [Singh et al. 2008]. OH OH CH O 2 OH O C OH + 2 N Br + H 2 O OH C D-Fru O NBP OH O O OH C + N H HO OH + 2HBr + C Arabinonic O NHP HO acid HCOOH (141) Formic acid The FTIR spectra of the main product showed a sharp band at (due to C=O stretching) and at (due to C-O stretching), suggesting the formation of carboxylic acid i.e. Formic acid and Arabinonic acid. The strong broad peaks in the ranges of indicated the presence of hydrogen bonded alcohols in arabinonic acid. Stretching at also showed presence of amines (N-H) i.e. phthalimide. A band observed at 1600 corresponds to the aromatic ring in phthalimide (Fig. 6.27). In Eq. (139) the main reaction products of the oxidation of D-Ara in the presence of Ru(III) chloride was identified as erythronic acid and formic acid. The oxidation product was identified by TLC and conventional spot test method [Singh et al. 2007]. 230

39 O O O OBr C O O C OH + 2 N Br + HO OH2 C OH C N H + 2HBr + HCOOH (142) O O D-Ara NBP Erythronic NHP OH Acid In Eq. (139) the main reaction products of the oxidation of D-Glu in the presence of Ir(III) chloride was identified as D-glucono-1.5-lactone. The oxidation product was identified by GCMS and TLC method. The formation of these products was confirmed by GC-MS analysis in which the reaction mixture was extracted with diethyl ether. The ether layer was concentrated by slow evaporation before analyzing with GC-MS, JEOL-JMS (Mate-MS system, Japan). NHP, i.e., the reduced product of NBP was also identified by GC-MS. HOH H O HO HO H H OH H OH o C H O C + 2 N Br + H 2 O HO + 2 N H (143) HO C H OH C O o H OH Glu NBP D-glucono-1,5-lactone NHP H o o In Eq. (139) the main reaction products of the oxidation of D-Mal in the presence of both catalysts Ru(III) and Ir(III) chloride was identified as arabinonic acid and formic acid. The oxidation product was identified by TLC and by spot test method method [Singh et al., 2002; Singh et al.; 2007]. C 12 H 22 O C 8 H 4 O 2 NBr + 5H 2 O 2HCOOH + 2C 5 H 10 O 6 + 4HBr + 5C 8 H 4 O 2 NH D-Mal NBP Arabinonic Acid (144) 6.3 MULTIPLE REGRESSION ANALYSIS In order to find out the relationship between dependent variable log k (calculated + observed + predicted) and independent variables, log [Ru(III)], log [H + ] and log [Cl - ], log [D-Ara] and log [D-Mal] in Ru(III) catalyzed oxidation of reducing sugars and log [Ir(III)], 231

40 log [H + ] and log [Cl - ], log [NHP] in Ir(III) catalyzed oxidation of reducing sugars to arrive at a conclusion whether the proposed mechanism is well in accordance with our experimental kinetic data or not, we have taken multiple regression analysis using the computer package STATGRAPHICS With the help of multivariate regression analysis, a relationship between observed pseudo first-order rate constant (k 1 ) and concentrations of all the reactants of the Ru(III) catalyzed oxidation of D-Fru was found to be: k 1 = k [Ru(III)] 0.61 [H + ] 0.75 [Cl - ] (145) Where k = 7.21 x 10-1 With the help of Eq. (145), the reaction rate predicted for the Ru(III) chloride, hydrogen and chloride ions, concentrations in the oxidation of D-Glu were found to be very close to the calculated and observed rates (Table 6.3:01). The close similarity among the three rates, i.e., the observed, calculated and predicted rates, clearly proves the validity of the rate law, and hence the proposed mechanism. 232

41 Table- 6.3:01 Comparison of observed rates in the variation of [Ru(III)], [H + ] and [KCl] with calculate and predicted rate for the oxidation of D-Fru with NBP at 303K. [Ru(III)] x10 5 (mol dm -3 ) [H + ] x 10 3 (mol dm -3 ) [KCl] x 10 5 (mol dm -3 ) k 1 x 10 4 (s -1 ) (Observed) k 1 x 10 4 (s -1 ) (Calculated) k 1 x 10 4 (s -1 ) (Predicted) k cal = calculated with the help of graph between log (a-x) vs time. k obs = Calculated on the basis of rate law. k pre = Calculated with the help of multiple regression analysis 233

42 With the help of multivariate regression analysis, a relationship between observed pseudo first-order rate constant (k 1 ) and concentrations of all the reactants of the Ru(III) catalyzed oxidation of D-Ara was found to be: k 1 =k[ru(iii)] 1.03 [H + ] 0.89 [Cl - ] 0.39 [D-Ara] 0.39 (146) Where k = 6.55 x 10 2 With the help of Eq. (146), the reaction rate predicted for the Ru(III) chloride, hydrogen, chloride ions and D-Ara concentrations in the oxidation of D-Ara were found to be very close to the calculated and observed rates (Table 6.3:02). The close similarity among the three rates, i.e., the observed, calculated and predicted rates, clearly proves the validity of the rate law, and hence the proposed mechanism. For the same analysis, the Ru(III) catalyzed oxidation of D-Mal was found to be: k 1 = k[ru(iii)] [H + ] 0.65 [Cl - ] 0.69 [D-Mal] 0.59 (147) Where k = 7.99 x 10 6 With the help of Eq. (147), the reaction rate predicted for the Ru(III) chloride, hydrogen, chloride ions and D-Mal concentrations in the oxidation of D-Mal were found to be very close to the calculated and observed rates (Table 6.3:03). The close similarity among the three rates, i.e., the observed, calculated and predicted rates, clearly proves the validity of the rate law, and hence the proposed mechanism. 234

43 Table- 6.3:02 Comparison of observed rates in the variation of [Ru(III)], [H + ], [KCl] and [D-Ara] with calculate and predicted rate for the oxidation of D-Ara with NBP at 308K. [Ru(III)] x 10 5 (mol dm -3 ) [H + ] x 10 3 (mol dm -3 ) [KCl] x 10 5 (mol dm -3 ) [D-Ara] x 10 3 (mol dm -3 ) k 1 x 10 5 (s -1 ) (Observed) k 1 x 10 5 (s -1 ) (Calculated) k 1 x 10 5 (s -1 ) (Predicted) k cal = calculated with the help of graph between log (a-x) vs T. k obs = Calculated on the basis of rate law. k pre = Calculated with the help of multiple regression analysis 235

44 Table- 6.3:03 Comparison of observed rates in the variation of [Ru(III)], [H + ], [KCl] and [D-Mal] with calculate and predicted rate for the oxidation of D-Mal with NBP at 308K. [Ru(III)] x 10 6 (mol dm -3 ) [H + ] x 10 2 (mol dm -3 ) [KCl] x 10 5 (mol dm -3 ) [D-Mal] x 10 3 (mol dm -3 ) k 1 x 10 4 (s -1 ) (Observed) k 1 x 10 4 (s -1 ) (Calculated) k 1 x 10 4 (s -1 ) (Predicted) , k cal = calculated with the help of graph between log (a-x) vs T. k obs = Calculated on the basis of rate law. k pre = Calculated with the help of multiple regression analysis With the help of multivariate regression analysis, a relationship between observed pseudo first-order rate constant (k 1 ) and concentrations of all the reactants of the Ir(III) catalyzed oxidation of D-Glu was found to be: 236

45 k 1 = k [H + ] 0.58 [Ir(III)] [Cl - ] 0.71 (148) Where, k = 9.33 x With the help of Eq. (148), the reaction rate predicted for the hydrogen, chloride ions and Ir(III) chloride concentrations in the oxidation of D-Glu were found to be very close to the calculated and observed rates (Table 6.3:04). The close similarity among the three rates, i.e., the observed, calculated and predicted rates, clearly proves the validity of the rate law, and hence the proposed mechanism. Table-6.3:04 Comparison of observed rates in the variation of [Ir(III)], [H + ] and [KCl] with calculate and predicted rate for the oxidation of D-Glu with NBP at 303K. [Ir(III)] x 10 6 (mol dm -3 ) [H + ] x 10 2 (mol dm -3 ) [KCl] x 10 5 (mol dm -3 ) k 1 x 10 5 (s -1 ) (Observed) k 1 x 10 5 (s -1 ) (Calculated) k 1 x 10 5 (s -1 ) (Predicted) k cal = calculated with the help of graph between log (a-x) vs T. k obs = Calculated on the basis of rate law. k pre = Calculated with the help of multiple regression analysis 237

46 With the help of multiple regression analysis, a relationship between observed pseudo first-order rate constant (k 1 ) and concentrations of all the reactants of the Ir(III) catalyzed oxidation of D-Fru was found to be: k 1 =k [Ir(III)] 0.58 [H + ] 0.66 [Cl - ] (149) Where, k = 1.28 x 10-2 With the help of Eq. (149), the reaction rate predicted for the Ir(III) chloride, hydrogen and chloride ions concentrations in the oxidation of D-Fru were found to be very close to the calculated and observed rates (Table 6.3:05). The close similarity among the three rates, i.e., the observed, calculated and predicted rates, clearly proves the validity of the rate law, and hence the proposed mechanism. For the same analysis, the Ir(III) catalyzed oxidation of D-Mal was found to be: k 1 =k[ir(iii)] 0.54 [H + ] [Cl - ] 0.52 [NHP] (150) Where k = 6.75 x 10-1 With the help of Eq. (150), the reaction rate predicted for the Ru(III) chloride, hydrogen, chloride ions and NHP concentrations in the oxidation of D-Mal were found to be very close to the calculated and observed rates (Table 6.3:06). The close similarity among the three rates, i.e., the observed, calculated and predicted rates, clearly proves the validity of the rate law, and hence the proposed mechanism. 238

47 Table- 6.3:05 Comparison of observed rates in the variation of [Ir(III)], [H + ] and [KCl] with calculate and predicted rate for the oxidation of D-Fru with NBP at 303K. [Ir(III)] x 10 5 (mol dm -3 ) [H + ] x 10 3 (mol dm -3 ) [KCl] x 10 5 (mol dm -3 ) k 1 x 10 4 (s -1 ) (Observed) k 1 x 10 4 (s -1 ) (Calculated) k 1 x 10 4 (s -1 ) (Predicted) k cal = calculated with the help of graph between log (a-x) vs time. k obs = Calculated on the basis of rate law. k pre = Calculated with the help of multiple regression analysis 239

48 Table- 6.3:06 Comparison of observed rates in the variation of [Ir(III)], [H + ] and [KCl] with calculate and predicted rate for the oxidation of D-Mal with NBP at 308K. [Ir(III)] x 10 5 (mol dm -3 ) [H + ] x 10 2 (mol dm -3 ) [KCl] x 10 5 (mol dm -3 ) [NHP] x 10 4 (mol dm -3 ) k 1 x 10 4 s -1 (Observed) k 1 x 10 4 s -1 (Calculated) k 1 x 10 4 s -1 (Predicted) , k cal = calculated with the help of graph between log (a-x) vs T. k obs = Calculated on the basis of rate law. k pre = Calculated with the help of multiple regression analysis 240

49 6.4 COMPERATIVE STUDY An attempt has been made to compare the experimental findings with the results obtained for the Ru(III) chloride catalyzed oxidation of D-Glu, D-Fru, D-Ara, D- Mal by NBP and Ir(III) chloride catalyzed oxidation of D-Glu, D-Fru and D-Mal by NBP in acidic medium. Participation of different reactive species have been reported in different reaction conditions, free NBP, itself was found be present as reactive species in case of Ru(III) catalyzed oxidation of D-Glu, D-Fru, D-Ara and Ir(III) catalyzed oxidation of D-Glu, D-Fru. Reactive species NBPH + was present during Ru(III) catalyzed oxidation of D-Mal whereas HOBr was present in case of Ir(III) catalyzed oxidation of D-Mal. Efforts have also been made to compare the findings of the reactive species of catalyst. The reactive species of Ru(III) chloride is [Ru(Cl) 3 (H 2 O) 2 OH] - for the oxidation of D- Glu, D-Fru, [RuCl 6 ] 3- for the oxidation of D-Ara and [Ru(Cl) 5 (H 2 O) 2 ] 2- for the oxidation of D-Mal in acidic medium. The reactive species of Ir(III) chloride is [Ir(Cl 6 )] 3- for the oxidation of D-Glu, D-Fru and [IrCl 5 (H 2 O)] 2- for the oxidation of D- Mal in acidic medium. The order of reaction with respect to Ir(III) catalyst was found zero, for all reducing sugars i.e., D-Glu, D-Fru and D-Mal. Reaction followed positive fractional order dependence on [Ru(III)] for the oxidation of D-Ara & D-Mal while D- Glu & D-Fru showed zero order dependence on [Ru(III)]. It can be concluded from activation parameters that the activation energy is the highest for the Ir(III) chloride catalyzed oxidation of D-Mal by NBP in acidic medium. The values of various activation parameters obtained are summarized in tables to

50 TABLE: 6.4:01 ACTIVATION PARAMETERS (In presence of Ru(III) chloride) Substrate ΔEa (kj mol -1 ) ΔH # (kj mol -1 ) ΔS # (JK -1 mol -1 ) ΔG # ( kj mol -1 ) log Pz D-Glu D-Fru D-Ara D-Mal TABLE: 6.4:02 ACTIVATION PARAMETERS (In presence of Ir(III) chloride) Substrate ΔEa (kj mol -1 ) ΔH # (kj mol -1 ) ΔS # (JK -1 mol -1 ) ΔG # ( kj mol -1 ) log Pz D-Glu D-Fru D-Mal

51 6.5 CONCLUSION Investigation of kinetics and mechanism of the transition metal catalyzed oxidation of reducing sugars by NBP in various reaction conditions may be helpful to understand the complicated biochemical and other problems in the living system. Oxidation of reducing sugars is of great importance both from a chemical and biological point of view, as reducing sugars play active role in biological systems. In the light of kinetic observations for the catalytic effect of Ru(III)/Ir(III) on the oxidation of reducing sugars by NBP, has been studied in acidic medium. Oxidation of reducing sugars (D- Glu, D-Fru, D-Ara and D-Mal) by NBP is very sluggish, but becomes facile in the presence of micro quantity of catalyst (Ru(III) or Ir(III) chloride. The observed catalytic potential gives useful information on the oxidation state of the catalyst. Through the kinetic study we proposed a simple reaction mechanism, which can very well explain the reaction. Oxidation products were identified. Activation parameters and rate determining step constant were calculated from the rate law derived from the proposed reaction mechanism. All the steps involve in the kinetics measurement including the value of Ea, ΔH #, ΔG # and ΔS # were used to establish the reducing sugar leading to the formation of acid. The present thesis provides comprehensive information about the reactivity of transition metal catalyzed oxidation of reducing sugars by NBP in acidic medium. It may find application in industries. It has also wide synthetic applications. The coming years promise to provide additional and challenging opportunities for the study of transition metal catalyzed oxidative degradation of reducing sugars by various oxidant in acidic media. Hence the reaction involving carbohydrates are of considerable interest. 6.6 FUTURE PROSPECT Carbohydrates are the structural backbone of the DNA, RNA and nucleic acids and play major role in nutrition. They are further important due to their wide occurrence and multihydroxy functionality that allows coordination and chelation to many metal ions. Trace amount of some transition metals are present in the human bodies which help in catalyzing carbohydrate in the body. This area of research is unattended Present study of oxidation kinetics of reducing sugars by NBP will provide a new field of academic interest in physio-chemical aspect of the reaction. The application of 243

52 homogenous catalysis by organometallic complexes looks very promising for cited reasons. Present study can act as model for oxidation of carbohydrates including reducing and non-reducing class with different inorganic and organic catalysis. Ru (III) and Ir (III) can act as catalyst in presence of NBP in unattended carbohydrates. This work opens new understanding of oxidation of sugars in acid medium. The study is environment friendly and unique. Thorough analysis of any energy and environmental considerations involved with these treatment methods would provide an important supplement to this study. With these conclusions in mind, further research should be conducted in order to make any viable suggestions for treatment. Interpreting such method is possible by GCMS/FTIR and can be investigated more easily. Additional techniques can be used to confirm the mechanism of interaction suggested by the present study. Studying more factors and conditions, such as ionic strength and ph may further clarify the mechanism of interaction. Present study will provide new understanding of catalysis of reducing sugars and can act as model for simulation in similar studies. Further research on sugar oxidation should be encouraged going by its biological importance. 244

53 BIBLIOGRAPHY Abou Ouf A, Walash M I, EI-Ashry S, J Drug Res, 1980, 12, p. 77. Abou Ouf A, Walash M I, Salem F B, Analyst, 1981, 106, p Ashish, Singh S P, Singh A K, Oxid Commu, 2005, 28(3), p Ashish, Singh S P, Singh A K, Singh B, J Mol Catal A: Chem, 2006, 266, p Arkin, M.R., Stemp, E.D.A., Coates, P.S., and Barton, J.K. Chemistry & Biology, 1997, 4, p Atkins P, Paula J D, Atkins Physical Chemistry, Oxford University Press, 2002, Ed VII. Bailar J C, The Chemistry of Co-ordination Compounds, Reinhold, NY, Bamford C H, Tipper C F H, Comprehensive Chemical Kinetics, Elsevier Publishing Company, NY, Berezin I U, Martinek, Yatsimirski A K, Russ Chem Rev, 1973, 42, p Bhattacharya N, Sengupta M L, Ind J Chem, 1967, 5A, p Bhutani S P, Carbohydrate, Ane Books Private Limited, Bierenstiel M, Transiton Metal Catalyzed Selective Oxidation of Sugars and Puyol, Organic Chemistry, Germany, 2005, Ed IX. Cady H H, Connick R E, J Am Chem Soc, 1958, 80, p

54 Carruthers E, University Press, Cambrigde, 2003, Ed III. Castellan G W, Physical Chemistry, Wiley Publishing Company, London, 1983, Ed III. Chang J C, Garner C S, Inog Chem, 1965, 4, p Chimatadar S A, Kini A K, Nandibewoor S T, Inorg React Mech, 2005, 5, p Christian G D, Analytical Chemistry, Wiley India Private Limited, 2007, Ed VII. Connick R E, Fine D A, J Am Chem Soc, 1960, 82, p Cotton FA, Wilkinson G, Advanced Inorganic Chemistry, Wiley-Interscience Publication, NY, 1988, Ed V. Cotton FA, Wilkinson G, Murillo CA, Bochman M, Advanced Inorganic Chemistry, Wiley-Interscience Publication, USA, Das A K, Das M, Indian J Chem, 1995, 34A, p Das A K, J Chem Res, 1996, 4, p Das A K, Coord Chem Rev, 2001, 213, p Das C M, Indrasenan P, Indian J Chem, 1984, 23A, p Das C M, Indrasenan P, Indian J Chem 1987, 26A, p Davfokratova T, Analytical Chemistry of Ruthenium, Academy of Sciences, USSR,

55 Day J C, Govindaraj N, McBain D S, Skell P S, Tanko J M, J Org Chem 1986, 51, p Domingos A P J, Domingos A M T S, Gabral J M P, J Inorg Nucl Chem, 1969, 31, p Edward J D, Inorganic Reaction Mechanism, John Wiley and Sons, Inc, NY, Feigl F, Spot Test in Organic Analysis, Elsevier, NY, Fine D A, Ph D Thesis, University of California, Barkeley, 1960, as quoted by Buckley R R, Mercer E E, J Phys Chem, 1966, 70, p Francis A C, Organic Chemistry, McGraw-Hill Higher Education, NY, 2000, Ed IV. Frost AA, Pearson RG, Kinetics and Mechanism, Wiley NY, 1961, Ed II. Gopalkrishnan G, Rai B R, Venkatasubramanian N, Ind J Chem, 1980, 198, 293. Gowda B T, Damodara N, and Jyothi K, Int J Chem Kinetics, 2005, 37, p Griffith W P, The Chemistry of Rare Platinum Metals, Inter Science, NY, 1967, p Gupta K K S, Debnath N, Bhattach N, J Indian Chem Soc, 2000, 77(1), p Gupta K K, Chatterjee U, Carbohydr Res, 1984, 126, p Gupta K K, Gupta S S, Basu S N, Carbohydr Res, 1979, 71, p. 75. Guptal K K S, Begum B A, Pal B, Carbohydr Res, 1998, 309, p Hui TW, Wong K Y, Shiu K K, Electroanal, 2005, 8, p

56 Isbell H S, Pigman W, Adv Carbohydr Chem, 1968, 23, p. 11. Isbell H S, J Res Bur Stand, 1932, 8, p Isbell H S, J Res Bur Stand, 1937, 18, p Isbell H S, J Res Bur stand, 1962, 66A, p. 3. Iyengar, T.A., and Puttaswami Mahadewappa, D.S. Carbohydr. Res., 1990, 204, p Joshi G K, Katre Y R, Singh A K, J Surf and Det, 2006, 9, p Kabir-ud-Din, Morshed A M A, Kham Z, Carbohydr Res, 2002, 337, p Kalyan K S Gupta, Debnath N, Bhattach N, J Indian Chem Soc, 2000, 77(1), p Katre Y R, Mudliar S R, Joshi G K, Singh A K, J Dispersion Sci Technol, DOI: / Katre Y R, Patil S, Singh A K, J Dispersion Sci Technol, 2009, 30, p Katre Y R, Sharma R, Joshi G K, Singh A K, J Dispersion Sci Technol, DOI: / Katre Y R, Singh M, Singh A K, J Dispersion Sci Technol, 2011, 32, p Katre Y R, Singh M, Singh A K, Tenside Surf Det, 2011, 48, p. 1. Katre Y R, Singh M, Patil S, Singh A K, Acta Phy Chim Sin, 2009, 25(2), p Katre Y, Nayak S, Sharma D N, Singh A K, Res Chem Intermed, DOI /s

57 Katre Y R, Singh M, Patil S, Singh A K, J Dispersion Sci Technol, 2008, 29, p Katre Y, Singh M, Singh A K, Tenside Surf Det, 2010, 47, p. 2. Khan Z, Babu P S S, Kabir-ud-Din, Carbohydr Res, 2004, 339, p Kini A K, Farokhi S A, Nandibewoor S T, Trans Met Chem, 2002, 27(5), p Kolvari E, Choghamarani A G, Salehi P, Shirini F, Zolfigal M A, J Iran Chem Soc, 2007, 4, p Kravtsov V I, Petrova G M, Russ J Inorg Chem, 1964, 9, p Laidler K J, Chemical Kinetics, McGraw-Hill Publication, NY, 1965, Ed II. Laidler K J, Chemical Kinetics, Pearson Education, New Delhi, 2009, Ed III. Laidler K.J, Saquet I M, J Phys Colloid Chem, 1950, 54, p. 519 Malode S J, Abbar J C, Nandibewoor S T, Inorg Chim Acta, 2010, 363, p Manibala, Singh H S, Krishna B, Tandon P K, J Indian Chem Soc, 1985, 62, p March J, Advanced Organic Chemistry: Reactions, Mechanisms and Structure, Wiley, NY, 1995, Ed III. Mohanty R K, Das M, Das A K, Ind J Chem, 1998, 37A, p. 34. Morrison R T, Boyd R N, Bhattacharjee S K, Organic Chemistry, 2011, Ed VII. Newell L C, Descriptive Chemistry, Publisher Boston, USA, D C Heath and Company,

58 Neyhart G A, Cheng C C, Thorp H H, J Am Chem Soc, 1995, 117, p Odebunmi E O, Iwarere S A, Owalude S O, Int J Chem, 2006,16, p Ogunlaja A S, Odebunmi E O, Owalude S O, J Sci Technol, 2009, 10, p Okoro H K, Odebunmi E O, Int J Phys Sci, 2009, 4(9), p Panda H P, Sahu B D, Ind J Chem, 1989, 28A, p.323. Panigrahi G P, Misra P K, Indian J Chem 1977, 15A, p Perlin A S, Can J `Chem 1964, 42, p Perumal S, Ganesan M, Ind J Chem, 1989, 28A, p Perumal S, Alagnmalain S, Selvaray S, Arumangam N, Tetrahedron, 1986, 42, p Peter Atkins, Paula J D, Oxford University Press Inc NY, 2002, Ed VII, p Poulsen I A, Garner C S, J Am Chem Soc, 1962, 84, p Puttaswamy, Mayanna S M, Ind J Chem, 1999, 38A, p. 77. Radhakrishanamurti P S, Janardhana, Ind J Chem, 1980, 9A, p Rajaram J, Kuriacose J C, Kinetics and Mechanisms Chemical Transformation, Macmillan India Limited, Ramachandrappa R, Puttaswamy MSM, Gowda N M, Int J Chem Kinet, 1999, 30, p Rangappa S K, Raghavendra P M, Mahadevappa S D, Rai L M K, Channe D, Proc, Indian Acad Sci, Chem Sci, 1998, 110(1), p

59 Rao V S, Ind J Chem, 1994, 33A, p. 69. Reddy C S, Vijaykumar T, Indian J Chem, 1995, 33A, p Ruff F, Komoto A, Furukawar N, Oal S, Tetrahedron, 1976, 32, p Sandu S, Sethuram B, Rao T N, J Indian Chem Soc, 1983, 60 p.198. Sharma J, Sah M P, J Ind Chem Soc, 1994, 71, p Shilov E A, Yasnikov A A, Urk Khim Zh, 1952, 18, p Shivananda K N, Lakshmi B, Jagdeesh R V, Puttaswamy, Mahendra K N, Appl Catal A: Gen, 2007, 326 (2), p Singh A K, Srivastava S, Srivastava J, Srivastava R, Singh P, J Mol Catal A: Chem, 2007, 278 p. 72. Singh A K, Chaurasia N, Srivastava J, Rahmani S, Singh B, Catal Letts, 2004, 95(3-4), p Singh A K, Chopra D, Rahmani S, Singh B, Carbohydr Res, 1998, 314, p Singh A K, Jain B, Katre Y R, Oxid Commun Lett, 2009, 32(2), p Singh A K, Jain B, Katre Y R, Oxid Commun Lett, 2009, 32(2), p Singh A K, Jain B, Negi R, Katre Y R, Singh S P, Sharma V K, Catal Lett, 2009, 131, p

60 Singh A K, Jain B, Negi R, Katre Y R, Singh S P, Sharma V K, Transition Met Chem, 2010, 35, p. 407 Singh A K, Jain B, Negi R, Katre Y R, Singh S P, Sharma V K, Synth React Inorg, Met- Org, Nano- Met Chem, 2010, 40, p. 71. Singh A K, Jain B, Negi R, Katre Y R, Singh S P, Sharma V K, Transition Met. Chem, 2009, 34, p Singh A K, Negi R, Jain B, Katre Y R, Singh S P, Sharma V K, I & EC Res, Indus Engg Chem Res, 2011, DOI: /ie101661m. Singh A K, Negi R, Katre Y R J Mol Catal A: Chem, 2009, 302, p. 36. Singh A K, Negi R, Jain B, Katre Y R, Singh S P, Sharma V K, Catal Lett, 2009, 132, p Singh A K, Rahmani S, Singh B, Singh R K, Singh M, J Phys Org Chem, 2004, 17, p Singh A K, Singh V, Rahmani S, Singh A K, Singh B, J Mol Catal A, 2002, 197, p. 91. Singh A K, Sachdev N, Shrivastava A, Katre Y, Singh S P, Synth React Inorg, Met-Org, Nano- Met Chem,, 2010, 40, p Singh A K, Singh V, Singh A K, Gupta N, Singh B, Carbohydr Res, 2002, 337, p

61 Singh A K, Singh V, Rahmani S, Singh A K, Singh B, J Mol Catal A: Chem, 2003, 197, p. 91. Singh A K, Singh V, Singh A K, Gupta N, Singh B, Carbo Res, 2002, 337, p Singh A K, Srivastava J, Rahmani S, J Mol Catal A: Chem, 2007, 271, p Singh A K, Srivastava J, Rahmani S, Singh V, Carbohydr Res, 2006, 341, p Singh A K, Srivastava S, Srivastava J, Singh R, J Mol Catal A, 2007, 342, p Singh AK, Singh R, Srivastava J, Rehmani R, Srivastava S, J Organometallic Chem, 2007, 692, p Singh, A.K., Singh, A.K., Singh, V., Rahmani, S., and Ashish and Singh, B. J. Chem. Res., 2006, 8, p. 56 Singh B, Singh N B, Saxena B B L, J Indian Chem Soc, 1984, 61, p Singh B, Singh P K, Singh D, J Mol Catal, 1980, 78, p Singh H S, Singh B, Singh A K, Carbohydr Res, 1991, 211, p Singh M P, Singh H S, Verma M K, J Phys Chem, 1980, 84, p.256. Singh N D, J Ind Chem Soc, 1986, 63, p Singh S P, Singh A K, Singh A K, Singh B, J Mol Catal A, 2008, 293, p. 97. Singh S P, Singh A K, Singh A K, J Mol Catal, 2008, 293, p

62 Solomons, Fryhle C B, Organic Chemistry, John Wiley Publication, 2008, Ed IX. Srivastava S, Singh B, J Indian Chem Soc, 1988, 65, p Srivastava S, Singh B, J Indian Chem Soc, 1992, 69, p Srivastava S, Singh B, Oxid Commun, 1989, 12, p Srivastava S, Singh B, React Kinet Catal Lett, 1989, 39, p Srivastava S, Singh B, Transition Met Chem, 1991, 16, p Srivastava S, Singh S, Oxid Commu, 2004, 27, p Srivastava S, Oxid Commun, 1994, 17, p Srivastava S, Singh S, J Indian Chem Soc, 2004, 81, p Srivastava S, Srivastava P, J Saudi Chem Soc, 2009, 13, p Srivastava S, Tripathi H, Singh K, Trans Met Chem, 2001, 26, p Steinfeld J I, Francisco J S, Chemical Kinetics and Dynamics, William L Hase, Prentice Hall, Inc, Sun L et al. J. Amer. Chem. Soc. 1999, 121, p Sussich F, Cesaro A, Carbohydr Res, 2000, 329, p. 87. Tandon P K, Mehrotra A, Srivastava M, Dhusia M, Singh S B, Transition Met Chem, 2007, 32 p

63 Taqui Khan M M, Chandraiah G R, Rao A P, Inorg Chem,1986, 25, p Tegginamath, Hiremath C V, Nandibewoor S T, J Phys Org Chem, 2007, 20, p. 55. Tripathi R, Upadhyay S K, Int J Chem kinet, 2004, 36, p Tripathi R, Kambo N, Upadhay S K, J Bulg Chem Ind, 2004, 75(1-2), p. 18. Upadhyay S K, Chemical Kinetics and Reaction Dynamics, Anamaya Publishers, Veisi H, Ghorbani V R, Tetrahedron, 2010, 66, p Venkatasubramanian N, Thiagarajan V, Can J Chem, 1969, 47, p Vogel I, Elementary Practical Chemistry, Part III, Longmans-Green:London, Weibel, M K, Bright H J, J Biochem, 1971, 124, p Wohl R A, Ber, 1919, 52, p. 51. Wright M R, An Introduction to Chemical Kinetics, Wiley Publication, Xiong J, Ye J, He X, Kexue K G C, Yu Gongcheng, 2000, 16(3), p.172. Yang H, Shen B, Peng T, Wang G, Tang Y, P Zhang P, Xuebao H D, Ziran Kexueban, 1996, 23(2), p Ziegler K, Spath A, Schaaf E, Schumann W, Winkelmann E, Liebigs Ann Che, 1942, 551, p. 80. Zumdahl S S, Zumdahl S A, Chemistry, Houghton Mifflin Company, 2003, Ed VII. Zumdahl S S, Zumdahl Susan A, Chemistry, Houghton Mifflin Company, 2003, Ed VI. 255

64 PUBLICATIONS [A] In Journals: 1. Ajaya Kumar Singh, Neerja Sachdev, Alpa Shrivastava; Yokraj Katre, Surya P. Singh; A Novel and Facile Oxidation of D-glucose by N-bromophthalimide in the presence of Chloro-complex of Ruthenium(III); Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry vol. 40, (2010) p , publisher: Taylor & Francis. 2. Ajaya Kumar Singh, Neerja Sachdev, Alpa Shrivastava, Bhawana Jain, Yokraj Katre; Oxidation of D-glucose by N-bromophalimide in the presence of chlorocomplex of iridium(iii): a kinetic and mechanistic study; Research on Chemical Intermediates DOI /s y, publisher: Springer. [B] Papers Communicated: 1. Kinetic and mechanistic investigation of chlorocomplex of ruthenium (III) and iridium (III) catalysed oxidation of D-Fructose by NBP in acidic medium. 2. Mechanistic study of novel oxidation of D-arabinose by N-bromophthalimide using micro-amount of chloro-complex of Ru(III) as a homogeneous catalyst in acidic medium. 3. Ruthenate ion catalysed oxidation of D-Maltose by NBP in acidic solution: A kinetic and mechanistic study. 256

65 4. Kinetic study of oxidation of D-Maltose by N-bromophthalimide in the presence of Ir(III) as a homogeneous catalyst in acidic medium. [C] Presented in the conference: 1. Oxidation of D-glucose by N-bromophalimide in the presence of chlorocomplex of Ir(III): a kinetic and mechanistic study. 47th Annual Convention of chemists 2010, Pt. RSSU Raipur, December 23-27, 2010, PHY (OP) Kinetic and mechanistic investigation of chlorocomplex of Ru(III) catalysed oxidation of D-Fructose by NBP in acidic medium National Seminar on Recent Trends in Chemical Sciences and Future Prospects, Govt. V. Y. T. PG. college, Durg, October 11-12, 2011, PP Mechanistic study of novel oxidation of D-Fructose by N-bromophthalimide using micro-amount of chloro-complex of Ir (III) as a homogeneous catalyst in acidic medium National Seminar on Emerging Trends in Chemical Sciences Nov 18-19, 2011, Kalyan Post Graduate College, Bhilai Nagar (Chhattisgarh), OP Mechanistic study of novel oxidation of D-arabinose by N-bromophthalimide using micro-amount of chloro-complex of Ru(III) as a homogeneous catalyst in acidic medium 257

66 AICON All India Conference Jan 20-21, 2012, Chhatrapati Shivaji Institute of Technology, Durg (C.G.), CheA1221 [D] Other achievement: *Paper accepted for oral presentation in 239th American Chemical Society National Meeting, San Francisco, CA (USA), March 21-25,

67 October 12, 2009 Dear Neerja Sachdev: Thank you for submitting a scientific paper for the 239th ACS National Meeting & Exposition. More than 12,000 attendees from all chemistry disciplines are expected to attend this five day scientific meeting which will be held on March 21 25, 2010 at the Moscone Center, San Francisco, CA. Each national meeting is announced to the scientific community through publication of the call for papers and the technical program inside the Societys official publication, Chemical & Engineering News (C&EN). Additional meeting information can be found at Verification of Paper Acceptance According to our records in the Program and Abstract Creation System (PACS), the following abstract has been accepted for presentation at the meeting: Kinetic study of oxidation of Glucose by N bromophthalimide in the presence of ruthenium(iii)chloride Session: General Papers Synthetic Chemistry Registration & Housing All attendees, including speakers and poster presenters, at ACS national meetings must register for the meeting in order to participate in the technical programs and meeting events. Sponsored speakers should contact the symposium organizer or division program chair to clarify the terms of their invitation and to determine who will complete the speakers registration. Attendees must display their badges at all times in order to be admitted to official ACS sessions and events. You can reserve a hotel room at an official ACS hotel in November 2009 and register for the meeting January 2010, at Registering before the early registration deadline allows you to take advantage of the lowest registration fees. Hotel rooms at the discounted ACS rates sell out very quickly, so do not wait to reserve your room. Cancellations & Withdrawals If you are unable to attend the meeting to make your presentation, it is important that you inform the program chair that you must withdraw from the meeting. If you have already registered or booked your hotel room before you find out you cannot attend, you should visit the meetings website to read the cancellation policy for registration and housing. 259

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70 Fig FTIR Analysis of D-Fru

71 Fig GCMS Spectra of D-Glu

72 Oxidation of d-glucose by N- bromophthalimide in the presence of chlorocomplex of iridium(iii): a kinetic and mechanistic study Ajaya Kumar Singh, Neerja Sachdev, Alpa Shrivastava, Bhawana Jain & Yokraj Katre Research on Chemical Intermediates ISSN Volume 38 Number 2 Res Chem Intermed (2012) 38: DOI /s y 1 23

73 Your article is protected by copyright and all rights are held exclusively by Springer Science+Business Media B.V.. This e-offprint is for personal use only and shall not be selfarchived in electronic repositories. If you wish to self-archive your work, please use the accepted author s version for posting to your own website or your institution s repository. You may further deposit the accepted author s version on a funder s repository at a funder s request, provided it is not made publicly available until 12 months after publication. 1 23

74 Author's personal copy Res Chem Intermed (2012) 38: DOI /s y Oxidation of D-glucose by N-bromophthalimide in the presence of chlorocomplex of iridium(iii): a kinetic and mechanistic study Ajaya Kumar Singh Neerja Sachdev Alpa Shrivastava Bhawana Jain Yokraj Katre Received: 27 May 2011 / Accepted: 17 August 2011 / Published online: 8 September 2011 Ó Springer Science+Business Media B.V Abstract The kinetics of Iridium (III) catalyzed oxidation of D-glucose [D-glu] has been studied by N-bromophthalimide [NBP] in the acidic medium (ph 1.3) at 303 K. The reaction followed first-order kinetics with respect to [NBP] from to mol dm -3. The results indicate the first-order kinetics in [iridium(iii)] chloride at lower concentrations from to mol dm -3 tends towards a zero order at its higher concentrations (up to mol dm -3 ). Zero-order kinetics with respect to [D-glu] from to mol dm -3 was observed throughout its variation. A positive effect on the oxidation rate was observed for [Cl - ] from to mol dm -3 and the rate of reaction decreased with increase in dielectric constant (decreasing acetic acid from 35 to 15%) of the medium. A negative effect was observed on the reaction rate for [H? ] from to mol dm -3. Addition of reduced product of oxidant, i.e., phthalimide from to mol dm -3 did not show a significant effect on the oxidation velocity. Rate of reaction increased with increase in ionic strength from to mol dm -3 of the medium, i.e., increase in [KNO 3 ]; the rate of reaction was increased. From the linear Arrhenius plot of log k 1 versus 1/T, the activation energy (Ea = kj mol -1 ) was calculated. With the help of the energy of activation, parameters such as enthalpy of activation A. K. Singh (&) B. Jain Department of Chemistry, Government V.Y.T.PG. Autonomous College, Durg, Chhattisgarh, India ajayaksingh_au@yahoo.co.in N. Sachdev Department of Applied Chemistry, Bhilai School of Engineering, Durg, India A. Shrivastava Department of Applied Chemistry, Shri Shankaracharya College of Engineering & Technology, Bhilai, India Y. Katre Department of Chemistry, Kalyan Mahavidyalaya, Bhilai Nagar Sect-7, Bhilai, India 123

75 Author's personal copy 508 A. K. Singh et al. (DH # = kj mol -1 ), entropy of activation (DS # = JK mol -1 ), Gibbs free energy of activation (DG # = kj mol -1 ) and frequency factor (Log A =-3.97) were also calculated. A suitable mechanism in conformity with kinetic observations was proposed to explain reaction stoichiometry and product analysis. Keywords Kinetics Oxidation N-bromophthalimide D-glucose Iridium(III) chloride Introduction Recently, much attention has been paid to N-halo compounds due to their ability to act as a source of halonium ions, hypohalite species, and nitrogen anion, which act as a base and nucleophile [1 3]. N-halo compounds have been extensively used as an oxidizing agent for catalyzed and uncatalyzed reactions [4 8]. Additionally, N-halo compounds have also been widely used as halogenating reagents for organic compounds [9 12]. In the recent years, transition metal ions, such as ions of osmium, ruthenium, and iridium either alone or as binary mixture as catalyst, have been applied in the oxidation of several redox processes [13, 14]. The mechanism of catalysis is quite complicated due to the formation of different intermediate complexes, free radicals, and different oxidizing states of catalyst [15, 16]. Iridium (III) chloride is an important platinum group metal ion and has been widely used as catalyst in various redox reactions [17, 18]. The potential of iridium(iii) chloride to act as a homogenous catalyst in the oxidation process was also recognized for the oxidation of ethanol [19], methanol [20], formic acid [21] reducing sugar [22], and glycine [23] by different oxidant in acidic medium. Glucose is the most important carbohydrates in biological processes. The study of carbohydrates is one of the most exciting fields of organic chemistry. Vast literature is available on the kinetics of oxidation of carbohydrates by various organic and inorganic oxidants [24 27]. This study reports for the first time the kinetics investigation of iridium(iii) catalyzed oxidation of D-glu by NBP in acidic medium at 303 K. The objectives of the present study are to ascertain real reactive species of catalyst and oxidant, to deduce the rate law consistent with kinetic results, to calculate activation parameters, and to elucidate the plausible reaction mechanism. Experimental Materials and methods Analytical-grade chemicals and double-distilled water were used throughout the investigation. N-bromophthalimide (Lancaster, 98%), was used as received. A solution of NBP was prepared in 80% acetic acid and stored in a black-coated flask in order to prevent photochemical deterioration. An aqueous solution of D-glu (AR grade) was always freshly prepared. Iridium(III) chloride solution was prepared 123

76 Author's personal copy Oxidation of D-glucose by N-bromophthalimide 509 by dissolving a known weight of iridium(iii) chloride (Johnson Matthey) in HCl of known strength, and stored in a black-coated bottle. A standard solution of KCl, HClO 4, and phthalimide was prepared and mercuric acetate (Loba Chem., Mumbai, India) was acidified (ph 1.3) with 20% acetic acid. Kinetic procedure All the kinetic measurements were carried out in a black-coated vessel at 303 K and performed under pseudo first-order condition with [D-glu][NBP]. The reaction was initiated by the rapid addition of known amounts of D-glu to a reaction mixture containing the required amount of the NBP, HClO 4, iridium(iii) chloride, mercuric acetate, acetic acid, and water in glass-stoppered Pyrex boiling tubes and thermostated at 303 K (ph 1.3). The progress of reaction was monitored by iodometric determination of unconsumed [NBP] in known aliquots of the reaction mixtures at different time intervals. Each kinetic run was studied for 75% reaction. The rate constant in each kinetic run was determined by plotting a graph between remaining log [NBP] versus time. Each kinetic run was studied for two half-lives of the reaction. The observed rates of reaction were within ±5% in the replicate kinetic run. Stoichiometry and product analysis Different ratios of NBP to D-glu were equilibrated at 303 K in the presence of a requisite amount of all reactants, i.e., perchloric acid, mercuric acetate and acetic acid under the condition of [NBP][D-glu] for 72 h. Determination of unconsumed NBP revealed that 2 mol of NBP were required for the oxidation of each mole of D-glu. Accordingly, the following stoichiometric equation could be formulated as: HOH o o H OH H O C H O C HO H+ 2 N Br + H H OH 2 O HO +2 N H OH C HO H OH O C o H o D-Glu NBP D-glucono-1,5-lactone NHP HO H ð1þ D-glucono-1,5-lactone was confirmed by GC-MS. For GC-MS analysis, the reaction mixture was extracted with diethyl ether and the ether layer was concentrated by slow evaporation. The product was analyzed by GC-MS, JEOL- JMS (Mate-MS system, Japan). Test for free radicals To test the presence of free radicals in the reaction, the reaction mixture with acryl amide was placed in an inert atmosphere for 24 h. When the reaction mixture was 123

77 Author's personal copy 510 A. K. Singh et al. diluted with methanol, it was found that there was no precipitate formed. This clearly showed free radicals were not formed in the redox reaction under investigation. Kinetic measurements and results Initially, the kinetics of the oxidation of D-glu by NBP in the presence of iridium(iii) chloride under acidic conditions was studied at several initial concentrations of all the reactants at 303 K. Considering NBP, D-glu, perchloric acid and iridium(iii) chloride as the main reactants, the general form of rate equation for the reaction can be written as Rate ¼ k 1 ½NBP Š a ½D-gluŠ b ½iridiumðIIIÞŠ c ½H þ Š d ð2þ Uniform pseudo-first-order rate constant (k 1 ) values for the variation of [NBP] clearly indicate that the order with respect to [NBP] is unity. This is also obvious from the plot of log remaining [NBP] versus time (Fig. 1). The values of rate (-dc/dt) at various concentration of [NBP] (from to mol dm -3 ) clearly showed first-order kinetics with respect to [NBP] (Fig. 2). Reactions have been studied for [D-glu] (from to mol dm -3 ) at constant concentration of all reactants at constant temperature. The rate constant values were found almost constant clearly indicates zero-order kinetics with respect to D-glu (Table 1). The reaction followed first-order to zero-order kinetics with respect to [iridium(iii)] chloride from to mol dm -3 (Fig. 3; Table 2). With increasing concentration of HClO 4 from to mol dm -3, the rate constant decreased from to s -1 (Table 2). The variation of [Cl - ] from to mol dm -3 had a positive effect from to s -1 on the reaction rate (Table 2). Rate of reaction decreased with increase in dielectric constant (D) Fig. 1 Plot between log [NBP] versus time at T = 303 K. [D-glu] = mol dm -3,[H? ] = mol dm -3, [iridium(iii)] = mol dm -3, [KCl] = mol dm -3, [Hg(OAc) 2 ] = mol dm -3 and CH 3 COOH = 20% 123

78 Author's personal copy Oxidation of D-glucose by N-bromophthalimide 511 Fig. 2 Plot between -dc/dt versus [NBP] at T = 303 K. [D-glu] = mol dm -3, [H? ] = mol dm -3, [iridium(iii)] = mol dm -3,[KCl]= mol dm -3, [Hg(OAc) 2 ] = mol dm -3 and CH 3 COOH = 20% Table 1 Effect of variation [NBP] and [D-glu] on the rate of oxidation of D-glu at 303 K The solution conditions were [Hg(OAc) 2 ] = mol dm -3, [KCl] = mol dm -3, [KNO 3 ] = mol dm -3 and CH 3 COOH = 20% [NBP] mol dm -3 [D-glu] mol dm -3 k s (decreasing % acetic acid) of the medium. The effect of ionic strength (I) of the medium on the rate was studied using the KNO 3 solution, keeping the other experimental conditions constant. A positive effect of ionic strength of the medium was observed for the iridium(iii)-catalyzed reaction (Table 3). Increasing [mercuric acetate] and [NHP] did not affect the reaction rate (Table 3). The effect of temperature on the reaction rate was determined by keeping constant concentration of other constituents of the solution. The values of rate constants (from to s -1 ) observed at five different temperatures (from 298 to 318 K) were utilized to calculate the activation parameters. From the linear Arrhenius plot of log k 1 versus 1/T (Fig. 4), the activation energy (Ea = kj mol -1 ) was calculated. With the help of the energy of activation, parameters such as enthalpy 123

79 Author's personal copy 512 A. K. Singh et al. Fig. 3 Plot between rate constant versus [iridium(iii)] at T = 303 K. [NBP] = mol dm -3, [D-glu] = mol dm -3, [H? ] = mol dm -3, [KCl] = mol dm -3, [Hg(OAc) 2 ] = mol dm -3 and CH 3 COOH = 20%. [Hg(OAc) 2 ] = mol dm -3 and CH 3 COOH = 20% of activation (DH # = kj mol -1 ), entropy of activation (DS # = JK mol -1 ), Gibbs free energy of activation (DG # = kj mol -1 ) and frequency factor (Log A =-3.97) were also calculated. Discussion Reactive species of NBP It has been reported earlier by several workers [28 32] that NBP is a good oxidizing and brominating agent because of the large polarity of the [N Br bond. NBP, like other similar N-halo imides, may exist in various forms in acidic medium, i.e., free NBP, protonated NBP, Br?, HOBr (H 2 OBr)?, as per the following equilibrium: NBP þ H 2 O HOBr þ NHP ð3þ NBP þ H þ NHP þ Br þ ð4þ NBP þ H þ ðnbphþ þ ð5þ HOBr þ H þ ðh 2 OBrÞ þ ð6þ when (H 2 OBr)? is taken as the reactive species, the rate law obtained shows firstorder kinetics with respect to hydrogen ion concentrations, contrary to our observed negative fractional order in [HClO 4 ]. Therefore, the possibility of (H 2 OBr)? and cationic bromine (Br)? as reactive species is ruled out. When HOBr is assumed as the reactive species, the derived rate law failed to explain the negligible effect of phthalimide. Hence, neither of these species can be considered as the reactive species. Thus, the only choice left is NBP, which when considered as the reactive species, leads to a rate law capable of explaining all the kinetic observations and other effects. Hence, in the light of kinetic observation, NBP can safely be assumed to be the main reactive species for the present reaction. 123

80 Author's personal copy Oxidation of D-glucose by N-bromophthalimide 513 Table 2 Comparison of observed rates in the variation of [Ir(III)], [H? ] and [KCl] with calculated and predicted rate for the oxidation of D-glu with NBP at 303 K [Ir(III)] mol dm -3 mol dm -3 mol dm -3 (observed) [H? ] [KCl] k s -1 k s -1 (calculated) k 1 x10 5 s -1 (Predicted) k cal = Calculated with the help of graph between log [NBP] vs. T k obs = Calculated on the basis of rate law kpre = Calculated with the help of multiple regression analysis 123

81 Author's personal copy 514 A. K. Singh et al. Table 3 Effect of varying [NHP] and dielectric constant of the medium on the rate of oxidation of D-glu at 303 K l 9 10 mol dm -3 [NHP] mol dm -3 Acetic acid % by volume [Hg(OAc) 2 ] k s -1 mol dm Solution conditions were [NBP] = mol dm -3,[D-glu] = mol dm -3,[H? ] = mol dm -3, [Ir(III)] chloride = mol dm -3 Fig. 4 Plot between log k 1 versus 1/T at T = 303 K. [NBP] = mol dm -3,[D-glu] = mol dm -3, [Iridium(III)] = mol dm -3, [Hg(OAc) 2 ] = mol dm -3, [KCl] = mol dm -3 and CH 3 COOH = 20% 123

82 Author's personal copy Oxidation of D-glucose by N-bromophthalimide 515 Reactive species of Ir(III) chloride A spectrophotometric study of the kinetics of the hydration of [IrCl 6 ] 3- and of the addition of a Cl - to [Ir(H 2 O)Cl 5 ] 2- in M HClO 4 (or HCl) at 323 K was reported [33]. It is known that iridium(iii) chloride in hydrochloric acid gives [IrCl 6 ] 3- species [34]. It has also been reported that iridium(iii) and iridium(i) ions are the stable species of iridium [35]. Further, the equation of [IrCl 6 ] 3- gives [IrCl 5 H 2 O] 2-, [IrCl 4 (H 2 O) 2 ] - and [IrCl 3 (H 2 O) 3 ] species [36, 37]. This equilibrium may be shown by the general equation: ½IrCl 6 Š 3 þ n-h 2 O ½IrCl-ðH 2 OÞŠ 3 n þ Cl ð7þ when iridium(iii) chloride dissolved in 0.1 M HCl solution [IrCl 6 ] 3- and [IrCl 5 (H 2 O)] 2- species were formed. On the basis of the effect of chloride ions on the reaction rate, [IrCl 6 ] 3- have been considered to be the reactive species of iridium(iii) chloride. Considering the reactive species of Iridium(III) chloride and NBP with the help of the above experimental findings, the probable reaction mechanism is proposed, and considering the fact that 1 mol of D-glu is oxidized by 2 mol of NBP. On the basis of the observed kinetics result, [IrCl 2 (H 2 O) 2 (OH) 2 ] 2- as the most active species of iridium(iii) chloride and NBP itself as reactive species of NBP allowed us to propose a reaction Scheme 1. On the basis of steps (i) to (iii) in Scheme 1 for the oxidation of D-glu and considering the fact that 1 mol of D-glu is oxidized by 2 mol of NBP, the rate of reaction can be written as: Rate ¼ k½c 3 Š ð8þ On the basis of equilibrium steps (i) to (vii), Eqs can be written as: ½C 2 Š ¼ K ½ C 1Š½Cl Š ½H þ ð9þ Š ½C 3 Š ¼ K 2½C 2 Š½NBPŠ ½H þ Š ð10þ Rate ¼ kk 1K 2 ½C 1 Š½NBPŠ ½H þ ð11þ Š At any moment in the reaction, the total concentration of [NBP], i.e., [NBP] T can be shown as: ½NSBŠ T ¼ ½NBPŠþ½C 3 Š ð12þ On substituting the value of [C 3 ] from Eq. 11, we get Eq. 13 ½NBPŠ ½NBPŠ ¼ T ½H þ Š ½H þ ŠþK 1 K 2 ½C 1 Š½Cl Š ð13þ 123

83 Author's personal copy 516 A. K. Singh et al. From, Eqs. 8, 11, and 13, we get Eq. 14 Rate ¼ kk 1K 2 ½C 1 Š½Cl Š½NBPŠ T ½H þ ŠþK 1 K 2 ½C 1 Š½Cl ð14þ Š But ½C 1 Š ¼ ½IrðIIIÞŠ So Eq. 14 can be written as: Rate ¼ kk 1K 2 ½IrðIIIÞŠ½NBPŠ½Cl Š ½H þ ŠþK 1 K 2 ½IrðIIIÞŠ½Cl ð15þ Š Equation 15 is the rate law based on the observed kinetic orders with respect to each reactants of the reaction can be very easily explained. We can write Eq. 15 as Eq. 16: ½NBPŠ Rate ¼ ½ Š kk 1 K 2 ½IrðIIIÞŠ½Cl Š þ 1 ð16þ k According to Eq. 16, if a plot is made between [NBP]/rate versus 1/[Cl - ] and [H? ], a straight line having an intercept on y-axis will be obtained (Figs. 5, 6). This proves the validity of the rate law (15) and hence the proposed reaction Scheme 1. From the slope and intercept of the straight line, the values of k & K 1 K 2 have been calculated and found to be s -1, mol -1 dm 3, respectively. Utilized K 1 K 2 value, the reaction rates for the variation of [Cl - ] in the iridium(iii) chloride catalyzed oxidation of D-glu have been calculated by the help of rate law (16) and found to be very close to the rates observed experimentally. Effect of ionic strength The ionic strength (I) effect on the reaction rate has been described according to the theory of Bronsted and Bjerrum, which postulates the reaction through the formation of an activated complex. According to this theory, the effect of ionic strength on the rate for a reaction involving two ions is given by the relationship log k 1 ¼ log k 0 þ 1:02Z A Z B I 1=2 ð17þ here, Z A Z B are the valency of the ions A and B and k 1 and k 0 are the rate constants in the presence and absence of the added electrolyte, respectively. A plot of log k 1 against I 1/2 should be linear with a slope of 1.02 Z A Z B.IfZ A Z B have similar signs, the quantity Z A Z B should be positive, and the rate increases with the ionic strength, having a positive slope, while if the ions have dissimilar charges, the quantity Z A Z B should be negative and the rate would decrease with increase in ionic strength, having a negative slope. In the present study, a primary salt effect is observed as the rate increases with increase in ionic strength of the medium supporting the involvement of ions of same sign in the rate-determining step (Scheme 1). Positive slope obtained from the plot of log k versus I 1/2 clearly supports the step (III) of the Scheme H þ

84 Author's personal copy Oxidation of D-glucose by N-bromophthalimide 517 [IrCl 2 (H 2 O) 3 OH] + Cl - K 1 [IrCl 3 (H 2 O) 2 (OH) 2 ] 2- + H 3 O + (i) C 1 C 2 [IrCl 3 (H 2 O) 2 (OH) 2 ] 2- K 2 + NBP [IrCl 3 (NBP)(H 2 O)(OH) 2 ] 2- (ii) -H 2 O C 2 C 3 [IrCl 3 (NBP)(H 2 O)(OH) 2 ] 2- k slow [IrCl 3 (OBr)(H 2 O)(OH)] 2- + NHP (iii) C 3 C 4 [IrCl 3 (OBr)(H 2 O)(OH)] 2- + D-Glu [IrCl3(OBr)(D-Glu)OH] 2- + H 2 O (iv) C 4 C 5 [IrCl 3 (OBr)(D-Glu)OH] 2- +3H 2 O [IrCl 2 (H 2 O) 3 OH] - + Cl - + O - H H O HO HO H H OH H OBr (v) C 5 C 6 O - H H O HO HO H H OH H OBr C 6 H OH H O HO HO H OH O H D-glucono-1,5-lactone (vi) HO HO H OH H H H O blue colour OH O alkaline NH 2 OH FeCl 3 +HCl H OH H OH O HO HO H H OH O D-gluconic acid ion FeCl 3 +phenol yellow colour (vii) Scheme 1 Reaction path for the oxidation of D-glu by NBP in the presence of Iridium(III) chloride 123

85 Author's personal copy 518 A. K. Singh et al. Fig. 5 Plot between [NBP]/rate versus [H? ] at T = 303 K. [NBP] = mol dm -3, [D-glu] = mol dm -3, [Iridium(III)] = mol dm -3, [Hg(OAc) 2 ] = mol dm -3, [KCl] = mol dm -3 and CH 3 COOH = 20% Fig. 6 Plot between [NBP]/rate versus 1/[Cl - ]att = 303 K. [NBP] = mol dm -3,[D-glu] = mol dm -3, [Iridium(III)] = mol dm -3, [H? ] = mol dm -3, [Hg(OAc) 2 ] = mol dm -3 and CH 3 COOH = 20% Effect of dielectric constant and calculation of the size of an activated complex (d AB ) in the oxidation of D-glu In order to determine the effect of dielectric constant of the medium on the reaction rate, the reaction has been studied with different dielectric constant (D) of the medium at constant concentration of all other reactants at constant temperature. It is clear from Table 3 that k (rate constant) values decreased with the decreasing dielectric constant of the medium, i.e., increasing % of acetic acid. This effect is given by the following equation: Z A Z B e 2 N log k 1 ¼ log k 0 2:303ð4pbÞd AB RT 1 ð18þ D 123

86 Author's personal copy Oxidation of D-glucose by N-bromophthalimide 519 where k 0 is the rate constant in a medium of infinite dielectric constant, Z A and Z B are the charges of reacting ions, d AB refers to the size of activated complex, and T is absolute temperature and D is the dielectric constant of the medium. The decrease in first-order rate constant with the increase in dielectric constant of the medium is also evident form plots of log k 1 and 1/D. The plot of log k 1 versus 1/D, was linear, having a negative slope was obtained, indicating an interaction between a charged ion and a dipolar molecule. The value of d AB value was evaluated with the help of the slope of the straight line and found to be 3.07 Å. Role of entropy of activation and other activation parameters Entropy of activation plays an important role in the case of reaction between ions or between an ion and a neutral molecule or a neutral molecule forming ions. When a reaction takes place between two ions of opposite charge, their union will result in a lowering of the net charge and, due to this, some frozen solvent molecules will be released with an increase of entropy. On the other hand, however, when a reaction takes place between two similarly charged species, the transition state will be a more highly charged ion, and due to this, more solvent molecules will be required than for the separate ions, leading to a decrease in entropy. On the basis of this information, observed negative entropy of activation in the oxidation of D-glu by NBP in the presence of iridium(iii) catalyzed supports the rate-determining step of the proposed Scheme 1. Values of frequency factor (A) and free energy of activation also support the reaction Scheme 1 proposed for the oxidation of D-glu. Multiple regression analysis With the help of multivariate regression analysis, a relationship between observed pseudo first-order rate constant (k 1 ) and concentrations of all the reactants of the reaction was found to be: k 1 ¼ k½h þ Š 0:58 ½iridiumðIIIÞŠ 0:60 ½Cl Š 0:71 ð19þ where k = With the help of Eq. 19, the reaction rate predicted for the hydrogen ions, chloride ions and iridium(iii) chloride concentrations in the oxidation of D-glu were found to be very close to the calculated and observed rates (Table 2). The close similarity among the two rates, i.e., the calculated and predicted rates, clearly proves the validity of the rate law (15), and hence the proposed mechanism. Comparative studies When an effort was made to compare the findings of iridium(iii) catalyzed oxidation of D-glu by NBP Ru(III) [38] catalyzed oxidation of D-glu, it was found that free NBP is the reactive species of NBP in each case. Zero-order kinetics in [D-glu] was observed for both iridium(iii) and Ru(III) systems clearly shows that there is no effect of [D-glu] on the rate of reaction. The present study shows 123

87 Author's personal copy 520 A. K. Singh et al. similarity with [Ru(III)] [38]-catalyzed oxidation of D-glu as for as formation of a complex between transition metal-catalyst (iridium(iii) and Ru(III)) with D-glu is concerned. Iridium(III) and Ru(III) systems show the same behavior in respect to the order in [Hg(II)] and [H? ]. The present study differs with respect to [Cl - ] and ionic strength of the medium with our earlier study [38]. A negative effect of [Cl - ] was observed in Ru(III), whereas a positive effect of [Cl - ] on the rate of reaction was observed in the present study. The rate of reaction was not influenced by the change in ionic constant (l) of the medium, whereas the rate of reaction increased with an increase in ionic strength of the medium in the present study. Conclusions Iridium(III) catalyzed oxidation of glucose by NBP was studied at 303 K. Oxidation of D-glu by NBP in acidic medium becomes facile in the presence of iridium(iii) chloride. Oxidation products have been identified. NBP itself and [IrCl 3 (H 2 O) 2 (OH) 2 ] 2- were identified as reactive species of NBP and iridium. Various activation parameters have been evaluated. In the scheme, each molecule of D-glu consumed 2 mol of NBP to D-glucono-1,5-lactone and phthalimide in agreement with the experimental observed stoichiometry. The deduced rate law from the reaction scheme was also consistent with kinetics of the reaction. Future studies on the iridium(iii) chloride catalyzed oxidation of other biological relevant carbohydrates by NBP would also be of interest. In conclusion, it can be said that iridium(iii) chloride is an efficient catalyst for the oxidation of D-glu by NBP in acidic medium. References 1. G. Chandra, S.N. Srivastava, J. Inorg. Nucl. Chem. 34, 197 (1972) 2. V.S. Rao, B. Sethuram, T.N. Rao, Int. J. Chem. Kinet. 11, 165 (1979) 3. A. Kantouch, S.H.A. Fattah, Chem. Zvest. 25, 222 (1971) 4. A.K. Singh, D. Chopra, S. Rahmani, B. Singh, Carbohydr. Res. 314, 157 (1998) 5. A.K. Singh, V. Singh, A.K. Singh, N. Gupta, B. Singh, Carbohydr. Res. 337, 345 (2002) 6. A.K. Singh, V. Singh, S. Rahmani, A.K. Singh, B. Singh, J. Mol. Catal. A Chem. 197, 91 (2003) 7. A.K. Singh, J. Srivastava, S. Rahmani, V. Singh, Carbohydr. Res. 341, 397 (2006) 8. A.K. Singh, V. Singh, Ashish, J. Srivastava, Ind. J. Chem. 45A, 599 (2006) 9. R. Khanchandani, P.K. Sharma, K.K. Banerji, Ind. J. Chem. 35A, 57 (1996) 10. K. Chaudhary, P.K. Sharma, K.K. Banerji, Int. J. Chem. Kinet. 31, 469 (1999) 11. S. Vyas, P.K. Sharma, Oxdn. Commun. 24, 248 (2001) 12. V. Kumbhat, P.K. Sharma, K.K. Banerjee, Int. J. Chem. Kinet. 34, 248 (2002) 13. B. Singh, S. Srivastava, Trans. Met. Chem. 16, 466 (1991) 14. R.V. Jagdeesh, Puttaswamy, J. Phys.Org. Chem. 21, 844 (2008) 15. A.K. Singh, R. Negi, Y.R. Katre, J. Mol. Catal A: Chem. 302, 36 (2009) 16. Y. Qing, H.M. Liu, G.Z. Yang, W.Y. Song, Y.K. Liu, Chem. Res. Chin. U. 23, 333 (2007) 17. V. Uma, B. Sethuram, T. Navaneet Rao, React. Kinet. Catal. Lett. 18, 283 (1981) 18. P.K. Tandon, S. Sahgal, A.K. Singh, S. Kumar, M. Dhusia, J. Mol. Catal. A: Chem. 258, 320 (2006) 19. R.K. Mohanty, M. Das, A.K. Das, Indian J. Chem. 37A, 34 (1998) 20. A.K. Das, J. Chem. Res. 4, 184 (1996) 123

88 Author's personal copy Oxidation of D-glucose by N-bromophthalimide A.K. Das, M. Das, Indian J. Chem. 34A, 866 (1995) 22. A.K. Singh, S. Rahmani, B. Singh, R.K. Singh, M. Singh, J. Phys. Org. Chem. 17, 249 (2004) 23. Ashish, S.P. Singh, A.K. Singh, B. Singh, J. Mol. Catal. A: Chem 266, 226 (2006) 24. S.P. Singh, A.K. Singh, A.K. Singh, J. Carbohydr. Chem. 28, 278 (2009) 25. M.A. Malik, S.A. AL-Thabaiti, Zaheer Khan, Colloids Surf. A 337, 9 (2009) 26. A.K. Singh, R. Singh, J. Srivastava, S. Rahmani, S. Srivastava, J. Organomet. Chem. 692, 4270 (2007) 27. A.K. Singh, S. Srivastava, J. Srivastava, R. Singh, Carbo. Res. 342, 1078 (2007) 28. V. Krishnakumar, V. Balachandran, T. Chithambarathanu, Spectrochim. Acta. A 62, 918 (2005) 29. A. Khazaei, A.A. Manesh, J. Braz. Chem. Soc. 16, 874 (2005) 30. A. Kirsch, U. Luning, J. Prakt. Chem. 340, 129 (1998) 31. A. Kirsch, U. Luning, U. Kruger, J. Prakt. Chem. 341, 649 (1999) 32. J.C. Day, N. Govindaraj, D.S. McBain, P.S. Skell, J.M. Tanko, J. Org. Chem. 51, 4959 (1986) 33. J.C. Chang, C.S. Garner, Inog. Chem. 4, 209 (1965) 34. F.A. Cotton, G. Wilkison, C.A. Murillo, M. Bochmannn, Adv. Inorg. Chem. (Wiley Interscience, New York, 1999), p V.I. Kravtsov, G.M. Petrova, Russ. J. Inorg. Chem. (Engl. Transl.) 9, 552 (1964) 36. I.A. Poulsen, C.S. Garner, J. Am. Chem. Soc. 84, 2032 (1962) 37. A.P.J. Domingos, A.M.T.S. Domingos, J.M.P. Gabral, J. Inorg. Nucl. Chem. 31, 2568 (1969) 38. A.K. Singh, N. Sachdev, A. Shrivastava, Y. Katre and S.P. Singh, Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chem. J. Inorg Nucl. Chem 40, 947 (2010) 123

89 This article was downloaded by: [singh, ajaya Kumar] On: 3 December 2010 Access details: Access Details: [subscription number ] Publisher Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: Registered office: Mortimer House, Mortimer Street, London W1T 3JH, UK Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry Publication details, including instructions for authors and subscription information: A Novel and Facile Oxidation of D-glucose by N-bromophthalimide in the Presence of Chloro-complex of Ruthenium(III) Ajaya Kumar Singh a ; Neerja Sachdev b ; Alpa Shrivastava c ; Yokraj Katre d ; Surya P. Singh e a Department of Chemistry, Govt. V. Y. T. PG. Autonomous College, Durg (C.G.), India b Department of Chemistry, Shri Shankaracharya Mahavidyalaya, Bhilai, India c Department of Applied Chemistry, Shri Shankaracharya College of Engineering & Technology, Bhilai, India d Department of Chemistry, Kalyan Mahavidyalaya, Bhilai, India e Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka, Japan Online publication date: 03 December 2010 To cite this Article Singh, Ajaya Kumar, Sachdev, Neerja, Shrivastava, Alpa, Katre, Yokraj and Singh, Surya P.(2010) 'A Novel and Facile Oxidation of D-glucose by N-bromophthalimide in the Presence of Chloro-complex of Ruthenium(III)', Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 40: 10, To link to this Article: DOI: / URL: PLEASE SCROLL DOWN FOR ARTICLE Full terms and conditions of use: This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, re-distribution, re-selling, loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.