Hamieda. E. Salman University of Krebala, College of Education (NJC) (Received on 23/3 /2008) (Accepted for publication 19/4 /2009)

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1 Natonal Journal of Chemstry,2009, Volume 35, Excess Molar Volumes of Bnary Mxtures of an Isomer of Pentanol +N-Methyl Morpholne an Interpretaton n Terms of the Prgogne-Flory- Patterson Theory Hameda. E. Salman Unversty of Krebala, College of Educaton (NJC) (Receved on 23/3 /2008) (Accepted for publcaton 19/4 /2009) Abstract The results of measurements of excess molar volumes V E at K over the whole mole fracton range for fve mxtures (N-methylmorpholne + 2-pentanol; + 3-pentanol;+ 3-methyl-1-butanol; + 2-methyl-1-butanol; and 2-methyl-2-butanol) are presented. The expermental values of V E show a negatve devaton from deal for the fve sets of bnary mxtures n except V E values for mxtures of (Nmethylmorpholne + 2-pentanol; and 3-pentanol) showes two structural regons. The frst s postve at mole fracton 0 X The second regon s negatve at mole fracton 0.25 X 2 1. The negatvty of V E ncreases n the order 2-methyl-2-butanol > 2-methyl-1-butanol > 3-methyl-1-butanol > 3-pentanol > 2-pentanol. The expermental results of V E are compared wth those predcted by the Prgogne- Flory- Petterson theory. The theory poorly predcts the expermental V E. The expermental value of excess molar volumes V E were ftted to the Redlch- Kster polynomal equaton to derve the bnary adjustable parameters and the standard devatons. The results obtaned are used to study the nature of molecular nteractons n these mxtures. As far as we know, n the open lterature, no study on mxtures contanng N-methylmorpholne الخالصة تم قياس الكثافة لمخالط ثنائية المكون من N- مثيل مورفالين مع ايزوم ارت مختلفة لكحول البنتانول V E عند درجة ح اررة , كلفن وعلى المدى التام من الكسور المولية. استتخدمت اليياستات اللمليتة للكثافتة لحستاج الحجتوم المولريتة الفائ تة الفائ تة مناقشة التأثي ارت المتبادلة لهذا النوع من المخالط.وقتد فشتلت نيريتة فلتورس لحستاج اليتيم اللمليتة لفتائ المولي لكل األمزجة التي تم د ارستها وهذا يدل على الفائ تتة تتتم تطبييهتتا نيريتتا باستتتخدام ملادلتتة ردلتت ومنهتا تتم الحجتم لف هذه النيرية.النتتائ اللمليتة المستحةتلة للحجتوم كستتتر للحةتتول علتتى ثوابتتت الملادلتتة وكتتذل النحتت ارف اليياسي عن النتائ اللملية. 467

2 Natonal Journal of Chemstry,2009, Volume 35 Introducton Excess Thermodynamc propertes of bnary mxtures contanng alcohol somers have been studed extensvely. These studes nclude the excess molar volumes (1,2) and the present work reports the molar excess volumes of bnary mxtures of pentanol s somers wth the N- methylmorpholne as a common solvent by measured the densty (ρ) over the entre composton range at K.We have used the Prgogne- Flory- Petterson (PFP) theory to nterpret the molar excess volumes of bnary mxtures of N- methylmorpholne + 2-pentanol; + 3- pentanol;+ 3-methyl-1-butanol; + 2- methyl-1-butanol; and 2-methyl-2- butanol at K over the whole mole fracton range to show that the Prgogne- Flory- Petterson (PFP) theory (3-5) may produce the observed volumetrc behavour for ths class of mxtures. ( I ) Ideal Mxture: The deal mxture s a hypothetcal one whose propertes are ntroduced nto the thermodynamc descrpton of real mxture as convenent standard of normal behavor. There s several defnton of an deal lqud mxture; one of the most convenent s that t s a mxture n whch the chemcal potentals of all components are gven the equaton: (6-8) t, x, t RT ln x......( 1), = 1, 2, 3,... Where, T and x s the chemcal potental and mole fracton of pure component,, at the same pressure and temperature as the mxture beng studed. For an deal mxture the molar functon of mxng are gven by the molar Gbbs functon mx G d m RT[ xln X (1 x) ln(1 X )]...(2) The molar entropy mx S d m R[ xln X (1 x)ln(1 X )]...(3) The molar enthalpy d mx H m The molar volume d mx V m ( 4) ( 5) 468

3 Natonal Journal of Chemstry,2009, Volume 35 For an deal mxture the molar Gbbs energy of mxng s negatve and the molar entropy of mxng s postve for any value of mole fracton. The molar functon of mxng for a bnary mxture [xa+(1- x)b], where x denotes the molar functon of A,are defned by : (II) Molar Mxng Functons * * mx X m X m xx (1 x) X......( 6) A B Where X m s the molar quantty of a bnary mxture [XA+(1-x)B] at the temperature T and pressure P and where X* A and X* B are the molar quanttes of the pure substances A and B at the same temperature and pressure. X denotes any extensve quantty such as G, H, S or V. Excess partal molar quanttes can be wrtten as the dfference between the partal molar quanttes for the non-deal mxture and those of an deal mxture. It has become customary to use nstead of the molar functon of mxng mxxm, the excess molar functon (9) : (III) Excess Functon E X X m mx m mx X d...(7) m so that excess means excess over deal. Thermodynamc functon lke Gbbs energy, molar polarzaton, entropy and enthalpy and excess molar volume are used by workers (10,11)) n nvestgatng the orentaton of molecular dpoles and molecular nteracton n bnary and ternary mxture n polar- polar, polarnon polar lquds. Payne and Theodorou (12) have suggested that the excess functon are more useful than the thermodynamc functons n nterpretng the molecular nteractons n such bnary mxtures. The mscblty between the two lquds n a mxture s maxmum when the molecular nteracton between them s more. The present paper studes the bnary mxtures contanng a methyl-2-butanol as co-solvent temperature K. Ths system s partcularly chosen n vew of ts mportance n chemcal engneerng desgn processes and polymer processng ndustres (16). Expermental Materals common solvent one of morpholne dervatves (13-15). We present here new expermental data on densty, ρ, and of N-methylmorpholne and 2- pentanol; 3-pentanol; 3-methyl-1- butanol; 2-methyl-1-butanol; and 2- The 2-pentanol, 3-pentanol, 3- methyl-1-butanol, 2-methyl-1- butanol, 2-methyl-2-butanol and N- methylmorpholne (pure grade) were obtaned from Aldrch. N- methylmorpholne was purfed as prevously descrbed (15).All solvents were checked by gas lqud at 469

4 Natonal Journal of Chemstry,2009, Volume 35 chromatographc analyss, densty. All bnary mxtures were prepared over the whole mole fracton range 0< 2 <1 usng Sartorus balance (precson 1x10-4 ) and ar tght stoppered bottles. The more volatle component lqud was drectly poured nto the bottle. The second component lqud was njected nto the bottle through the stopper by means of a syrnge. Ths procedure hndered any vapour loss and contamnaton. The mole fracton x of component lqud n the bnary mxture was calculated lqud n the bnary mxture was calculated from the followng relaton: x W W M M W j...(8) M j where W, M are the weght and the molecular weght of the component lqud. The possble error n the mole fracton s estmated to be lower than 2x10-4. The uncertanty n the mole fracton was ± Measurements: Denstes were measured wth a dgtal precson system DMA 60/602 (Anton Paar). Detals of the system and the calbraton procedure were adequately covered n prevous work (13). The reproducblty of densty measurements was ± g. cm -3. For all measurements, a Schott-Gerate CT 1150 thermostat was used at a constant dgtal temperature control of ±0.01 K at the desred temperature. Results and Dscusson The expermental results of densty, ρ of pure lquds and bnary mxtures of N-methylmorpholne and 2-pentanol; 3-pentanol; 3-methyl-1- butanol; 2-methyl-1-butanol; and 2- methyl-2-butanol at K are presented n Table 1. Excess molar volumes, V E for bnary mxtures have been calculated from the followng equatons (17). ( x M x M ) / ( x M / ) ( x M / )...(9) V / cm 3 mol where 1, 2 : mole fractons of lquds 1 and 2. M 1, M 2 : molar masses of lquds 1 and 2. ρ 1, ρ 2 : densty of lquds 1 and 2. ρ : densty of mxture. The obtaned results of for the mxture of N- methylmorpholne + 2-pentanol,+ 3- pentanol,+ 3-methyl-1-butanol,+ 2- V E methyl-1-butanol and 2-methyl-2- butanol at K are presented n Table

5 Natonal Journal of Chemstry,2009, Volume 35 The excess molar volumes V E for the bnary mxtures of N- methylmorpholne,+ 2-pentanol,+ 3- pentanol are show two structural regons exst over the entre composton range. In the frst, the 2- pentanol and 3-pentanol regons , ths shows a postve devaton, from deal as shown n Fg. 1. Ths behavor may be explaned qualtatvely: () Strong self assocaton n 2- pentanol, 3-pentanol through hydrogen bondng. () Sterc effect of methyl group connected to ntrogen atom wth lone pars of electrons n N-methylmorpholne prevent any molecular nteractons between the hydroxyl group of, 3- pentanol and the lone par of electrons on the ntrogen atom. n V E 3 1 ( cm mol ) x(1 x) A (1 2x) 0 () Added 2-pentanol, 3-pentanol to N-methylmorpholne enhances the N- methylmorpholne structure. In the second regons of 2- pentanol and 3-pentanol and The excess molar volumes V E for the bnary mxtures of N- methylmorpholne,+ 3-methyl-1- butanol; 2-methyl-1-butanol; and 2- methyl-2-butanol shows a negatve devaton, from deal as shown n Fg. 1. Ths behavor due to a strong hydrogen bondng between the hydroxyl groups of alcohols and the lone par of electrons on the ntrogen atom and destroyng the selfassocaton n alcohols leadng to gve negatve V E. It seems that the methyl group has no effect on the molecular nteractons between the solvent and co-solvent. Each set of results was ftted to the Redlch- Kster equaton (18-20)...(10) The correspondng coeffcents A are gven n table 2, together wth standard devaton (σv E ) defned as : E n E E 2 1/ 2 V ( ( Vexp Vtheor ) /( N n))...(11) 1 Where N s the number of data ponts and n s the number of coeffcents. Where s the mole fracton of pentanol somers. Theoretcal Predcton of Excess Molar Volumes Flory Theory The excess molar volumes for all bnary mxtures studed here were predcted usng the theory of Flory (3-5,21). Accordng to Flory, 471

6 Natonal Journal of Chemstry,2009, Volume 35 molecule n lqud s consdered to be made up of segments each havng a hard core volume * but occupyng ~ / *... (12 ) an effectve volume ~ n the lqud. The reduced volume For pure lqud was calculated from thermal expanson coeffcent accordng to Flory formula ~ [( 14/3 )/(1 )] 3...( 13) Where s the coeffcent of thermal expanson calculated from measured denstes ρ at two temperatures (ln 2ln 1)/( 2 1).....(14) The characterstc pressure P* and temperature T* are obtaned from the relaton P ~ /...(15) * 2 beng the sothermal compressblty and ~ /... (16) * Where at zero pressure the reduced volume and temperatures satsfy the reduced equaton of state. ~ ~ ~ T ( 1/ 3 1)/ 4 / 3...( 17 ) The reduced temperature approprate for a mxture of two components (ndcated by subscrpts 1 and 2) at mole fracton x s ~ ~ ~ T ( 1* T 2 * T )/( 1 1* 2* )...( 18) Where X 12 s a constant characterzng the dfference n the energy of speces 1 and 2. The segment or hard core volume fracton, s defned by 1 2) x1v 1*/( xv 1 1* x 1 ( 2v2 And the surface fracton *)...( 19) 2 ( 1 1) 2S 2/( 1S 12S 2)...( 20) 472

7 Natonal Journal of Chemstry,2009, Volume 35 S beng the molecular surface /volume rato n the absence of a value for X 12 (e.g. from measured values of excess heats of mxng) T ~ For the soluton s gven by equaton 18 whch, takng X 12 = 0 reduces to ~ ~ ~ T ( P1 * T1 2P 2* T2)/( 1P 1* 2 1 P 2*)...( 21) Excess molar volumes were there calculated from the followng equaton Where V E ~ ~ xv 1 1* x2v 2* /3( 1V 12V 2) 2 7 / 3 ~ T...( 22) ~ ~ ~ ~ 1 4 [( 1 2 ) 3 1]/( 1 2 ) 3...( 23) The parameters of the pure component lquds molar volume,v, thermal expanson coeffcent,, characterstc volume,, characterstc temperature, T, reduced volume, ~ and reduced temperature T ~ were calculated from equatons (12-23) are parmeterued for computng the excess molar volumes V E of the bnary mxtures n ths study are lsted n Table 3. Predcted V E values and the expermental values over the entre composton range at K are lsted n Table 4 wth the expermental data. We observed poor a agreement between the expermental values and the predcted ones. The theory fals to predct the excess molar volumes of polar polar mxtures. Ths ndcates that Flory theory dd not take n account the polarty effect n these mxtures. 473

8 Natonal Journal of Chemstry,2009, Volume 35 Table (1). Expermental Values of the densty () and Excess molar volume (V E ) of 1 N-methylmorpholne and 2 Isomerc pentanols mxtures at 298 K. ρ/ V E / 2 g.cm -3 cm 3 mol -1 ρ/ V E / 2 g.cm -3 cm 3 mol -1 1 N-methylmorpholne + 1 N-methylmorpholne pentanol 2 3-pentanol Table (1) cont. ρ/ V E / 2 g.cm -3 cm 3 mol -1 ρ/ V E / 2 g.cm -3 cm 3 mol -1 1 N-methylmorpholne methyl 1-butanol 1 N-methylmorpholne methyl-1-butanol

9 Natonal Journal of Chemstry,2009, Volume 35 Table (1) cont. ρ/ V E / 2 g.cm -3 cm 3 mol -1 1 N-methylmorpholne methyl 2-butanol Table (2). Polynomal Coeffcents and Standard Devatons σ, Obtans for Fts of Eqn. 10 to the V E Composton Data for the bnary Systems at K. system A ه A 1 A 2 A 3 σ 1 N-methylmorpholne pentanol N-methylmorpholne pentanol N-methylmorpholne methyl-1-butanol N-methylmorpholne methyl-1-butanol N-methylmorpholne methyl-2-butanol

10 Natonal Journal of Chemstry,2009, Volume 35 Table (3). Parameters of the pure lquds accordng to the Flory theory at K. Lqud V/Lmol (K -1 ) V * T * (K) ν ~ / Lmol -1 T~ N-methylmorpholne pentanol pentanol methyl-1-butanol methyl -1-butanol methyl -2-butanol Table (4). Excess molar volume (V E ) from Expermental and the predcted by Flory Theory. 2 V E (exp.) V E (ther.) 2 V E (exp.) V E (ther.) 1 N-methylmorpholne pentanol 1 N-methylmorpholne pentanol

11 Natonal Journal of Chemstry,2009, Volume 35 Table (4) cont. 2 V E (exp) V E (ther) 2 V E (exp) V E (ther) 1 N-methylmorpholne methyl 1-butanol 1 N-methylmorpholne methyl-1-butanol Table (4) cont. 2 V E (exp) V E (ther) 1 N-methylmorpholne methyl 2-butanol

12 V / cm. mol E 3-1 Natonal Journal of Chemstry,2009, Volume Fg. 1- Excess molar volumes V E, at K versus 2, the mole fracton of Isomerc Pentanols: ( ) 2-pentanol;( ) 3- pentanol;( ) 3-methyl-1- butanol; ( ) 2-methyl-1- butanol; and ( ) 2-methyl-2-butanol. References 1- G.C.Franchn, A.Mrchett, L.Tasse and G.Tos, J. Chem. Soc. Faraday Trans. I, 1988, 84, G.C.Franchn, A.Mrchett,C.Part, L.Tasse and G.Tos, J. Chem. Soc. Trans. I, 1989, 85, P. J. Flory, J.Am. Chem. Soc., 1965, 87, T. A. Salman Ph.D.Thess, Unversty of Al- Nahreen, College of Scence (2001). 5- H. T. Van and D. J. Patterson, J. Soln. Chem., 1982, 11, E. Brandstat, V. George and A. Kolbe, J. Mol. Lq., 1985, 31, B. B.Swan and G. S. Roy, Jpn,. J. Apl. Phys., 1986, 25, S. Trpathy, B. B. swan, Chem. Papers., 1991, 45, A.M.Awwad and E. I. Allos, J. Soluton Chem., 1987, 16(6), A. M. Awwad ;S.F. Al-Modfa and K. A. Jbara, J. Chem. Thermoldyn., 1985, S.F. Al-Modfa, A. M. Awwad and K. A. Jbara, Thermochemcal Acta, 1985, 84, R. Payne, I, Theodorou, J. Phys. Chem., 1972, 76, S.F. Al-Azzaw, and A. M. Awwad, J. Chem. Eng. Data, 1990, 35, A. H. Al-Dujal; A. A. Yassen and A. M. Awwad, J. Chem. Eng. Data, 2000, 45, S. F. Aghamr, H. Modarress and G. A. mansoor, J. Phys. Chem., 2001, 14, H. Shekaar and H. Modarress, J of Sc Islamc Repuplc of Iran, 2003, 14 (2),

13 Natonal Journal of Chemstry,2009, Volume E. Jmenez, C. Franjo and M. I. Pazandrade, J. Chem. Eng. Data, 1997, 42, A. M. Awwad, A. H. Al-Dujal and H. A. Salman, J. Chem. Eng. Data, 2002, 47, A. H. Al-Dujal; A. M. Awwad and H. A. Salman, Iraq J. Sc., 2001, 42, W. L Weng, J. Chem. Eng., 2000, 45, A. M. Awwad and K. A. Jbara, Flud Phase Equlbra, 1989, 47,