Journal of Chemical and Pharmaceutical Research

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1 Available n line Jurnal f Chemical and Pharmaceutical Research ISSN N: CODEN(USA): JCPRC5 J. Chem. Pharm. Res., 010, (6): Electrical cnductivity f s-acetylthichline halides and perchlrate in n-butanl Aida I. Kawana, Nasr H. El-hammamy*, Nabila M.El-Mallah and Heba M. Mharem Department f Chemistry, Faculty f Science, Alexandria University, Alexandria, Egypt, P.O. 46 Ibrahimia, Alexandria 131, Egypt ABSTRACT The cnductance f s-acetylthichline halides and perchlrate has been measured in n- butanl at 5 C.The data were analyzed using the Fuss=Onsager equatin fr 1:1 assciated electrlytes and the characteristic functin, Λ (equivalent cnductance at infinite dilutin), a (cntact distance f apprach) and K A (assciatin cnstant) has been derived. The assciatin cnstant K A was analyzed n the basis f the slvent separated-in pair mdel. INTRODUCTION Studies n electrlytic cnductance f acetylthichline halides and perchlrate slutins in water, methanl, ethanl and n-prpanl at 5 C, have been reprted recently (1-4). The paper represents a precise study f the cnductance f acetylthichline halides and perchlrate in n- butanl at 5 C in rder t thrw light n the behaviur f the behaviur f these salts in simple slvents. EXPERIMENTAL SECTION n-butanl, s-acetylthichline brmide, idide and perchlrate were purified as reprted elsewhere (5, 6). The specific cnductance fr cnductivity n-butanl (after purificatin) was fund tbe ( ) Ω -1 cm -1. The density f n-butanl was determined using 5ml pyknmeter at 5 ± 0.0 C and was fund t be g / cm 3. Its viscsity was measured at 5 ± 0.0 C using the viscmeter with a flw-time at 50 s fr water. It was fund t be p. The dielectric cnstant value used was that reprted by Evans and Gardam (7). 301

2 Cnductance Measurements Cell with bright platinum electrdes and a cell cnstant f 0.1 cm -1. Cnductance meter (mdel Crisn Cl P31), was used fr measuring the specific cnductance f dilute slutins Preparatin f Slutins All slutin were prepared by weight reduced t vacu. Salts were weighed by difference n a micrbalance which reads t ± 0.1 mg. Dilutin were carried ut successively int the cell by siphning the slvent by means f weighing pipette. RESULTS AND DISCUSSION The measured equivalent cnductance are shwn in Table I. An apprximate value f Λ (estimated frm the extraplatin f Λ vs C 1/ plt) intrduced t Fuss-Kraus-Shedlvsky (F.K.S.) equatin, t btain accurate values, 1 ΛS (z) 1 (CΛC(z) f ) = + (1) Λ K Λ D Where K D is the dissciatin cnstant and S (z) is the Shedlvsky ' s functin which was tabulated by Daggett fr different values f z. The value f z culd be calculated frm the fllwing equatin z 3/ ( ) / Λ = α CΛ () Α in the equatin is the limiting tangent. The plt f /ΛS (z) vs (CΛS (z) f ) gives 1/ Λ as the intercept and 1/ K D Λ as the slpe. Mre accurate values f Λ, a and K A are btained frm Fuss-Onsager equatin (8), with the aid f special cmputer prgram (IBM PC) starting with the value Λ which was btained previusly frm (F.K.S.) equatin. The accuracies required in these cmputatin are ± 0.0 fr Λ ; ± fr J <00, ± 5 fr J = ( ) and ± 10 fr J > Fig. 1 shws the variatin f a with J. By the aid f this calibratin curve, the average value f a determined frm the crrespnding average value f J (which is previusly btained frm the cmputer readings) Knwing that J is a functin f a and is represented by the fllwing equatin (8) J = σ 1 Λ + σ (3) where σ 1 and σ are the functin f J. The derived cnstants are represented in Table II. Λ increases frm acetylthichline brmide t perchlrate accrding t the inic equivalent cnductance f anins, The values f a decrease with increasing the size f anins indicating that it cntrls the extent f in pairing. The salvatin f these anins increases in the rder: Br - > I - - > ClO 4,which is in accrdance with the trend f a values. Frm the electrstatic pint f view, since the distance between the catin and the anin increases in the same rder, the frce f attractin increase in the rder: ClO - 4 > I - > Br -. And the trend K A increases with increase the size f anin (except I - ). In the earlier study (-4) n the cnductance f s-acetylthichline halides and perchlrate in methanl, ethanl and n-prpanl at 5 C authrs fund that the rder f salvatin (a ) is Br - > I - > ClO 4 - while K A (in methanl) increases frm ClO 4 - t Br - in the trend : ClO 4 - > I - > Br -, K A (in ethanl) increases frm ClO 4 - t Br - in the trend : ClO 4 - > I - > Br -, while K A (in n-prpanl) is 30

3 irregularly varied with the size f anin. The gradual decrease f a with the K A amng the studied salts was attributed t the relative psitin f the anin with respect t the catin which may nt be cmpletely spherical. Cnductance measurement f acetylchline halides and perchlrate in n-butanl at 5 C (5) gives the rder f salvatin (a ) as Cl - > Br - >I - > ClO 4 - and the trend f K A regularly increase with increase f the size f anin (except idide) which is als similar t present wrk. The increase f K A with increasing the size f anin f s- acetylthichline halides and perchlrate can be explained in the light f the U term included in the fllwing equatin (9) ln K A = ln (4 π Na 3 /3000) + (e / a DkT) + U (4) where, U = S / k - E s / KT S / k is the entrpy Bltzman cnstant rati which illustrates the prbability f the rientatin f slvent mlecules arund the free ins, and E s / KT is an energy relatinship which includes the energy f slvent mlecules with respect t bth free in and in-pair. The values f U term f s-acetylthichline halides and perchlrate are given in Table III. The result reveal that the value f U slightly decrease frm Br - t ClO 4 -. The in diple term becmes mre predminant than the entrpy term. Therefre the slvent separated in-pair mdel can be nw applied (10). In this mdel a multiple step assciatin is suggested and can be illustrated by the fllwing scheme: The assciatin cnstant is given by the fllwing expressin: K A = K Σ = [inpairs] = K + 1 (1+K ) (5) [(Acetylthichline) ] [X (slvent) ] n where, K A = K Σ is btained frm the cnductance measurements and b = a e DkT K 1 4π N a = b e (6) 303

4 K was thus calculated. The results cmplied in TABLE III, indicate that K 1 increases frm Br - t ClO 4 - i.e., the in-pair prefers the mre slvated frm (case I) than the deslvated frm (case II). The electrstatic radius (R + r R - ) is given by Stkes ' equatin, R ± = / λ ± η (7) Where λ - is btained frm the intercept f the straight line resulting frm the plts f Walden prduct Λ η vs the reciprcal f the mlecular weight as previusly discussed (5), where λ + fr s-acetylthichline + represented by the average value f λ + f the brmide, idide and perchlrate salts. Frm the data in TABLE IV, it can be seen that the values f a are smaller than the electrstatic radii (R + +R - ) which btained frm Stkes, equatin. This is due t the assciatin f ins (5). TABLE.I: Cnductance f Acetylthichline salts in n-butanl at 5 C Acetylthichline brmide Acetylthichline idide Acetylthichline perchlrate 10 4 C * Λ ** 10 4 C Λ 10 4 C Λ * equiv L -1 ** hm -1 equiv -1 cm TABLE:II. Characteristic parameters fr Acetylthichline salts in n-butanl at 5 C salts Λ (hm -1 equiv -1 Ac.Th. I cm ) ± ± ± J K A a (Ǻ) σ Λ TABLE:III. Calculated values f K and U f Acetylthichline Haides and Perchlrate in n-butanl at 5 C salts K A K 1 K U TABLE:IV. Calculatin f the radii f the ins fr Acetylthichline salts in n-butanl at 5 C salts Λ (1) () λ η - λ (1) + (1) λ + (1) Av. λ R + (Ǻ) R - (Ǻ) ± (1) hm -1 equiv -1 cm () hm -1 equiv -1 cm p R + +R a (Ǻ)

5 a Ac.Th ClO J J a 0 Fig.1: Variatin f J and a in n-butanl at 5 C REFERENCES [1] Nasr.H. El-Hammamy, Aida I. Kawana, Mustafa M. El-Khly, Mhamed F. Amira and Ghada A. Ibrahim, Alex. J. Pharm. Sci., 3 (), 79-81(009). [] Nasr.H. El-Hammamy, Aida I. Kawana, Shawky El-Shazly and Heba M. Mharem, Alex. J. Pharm. Sci., submitted fr publicatin (010). [3] N.H. El-Hammamy, A.M. Ismaeil and M.F. Amira and N.S. El-Sisy, J. Indian Chem. Sc., 86, (009). [4] A.I. Kawana, M.T. Mhamed and N.H. El-Hammamy, J. Indian Chem. Sc., 84, (007). [5] N.H. El-Hammamy, A,I.Kawana, Sh.A. El-shazly and F.F. El-bardisy, Bull. Electrchem., (1994). [6] A.I. Kawana, Bull. Electrchem., 16, 5 (000). [7] D.F. Evans and P. Gardam, J. Phys. Chem., 7, 381 (1968). [8] R.M. Fuss and L.Onsager, J. Phys. Chem.,61, 668 (1957); J. Amer. Chem. Sc., 81, 659 (1959). [9] F. Accascina, A. D ' Apran and R. Tril, J. Phys. Chem., 71, 3469 (1967). [10] D.F. Evans and P. Gardam, J.Phys. Chem., 73, 158(1969). 305