Available n line www.jcpr.cm Jurnal f Chemical and Pharmaceutical Research ISSN N: 0975-7384 CODEN(USA): JCPRC5 J. Chem. Pharm. Res., 010, (6):301-305 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 (5-8 10-8 ) Ω -1 cm -1. The density f n-butanl was determined using 5ml pyknmeter at 5 ± 0.0 C and was fund t be 0.8057 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 be0.0589 p. The dielectric cnstant value used was that reprted by Evans and Gardam (7). 301
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 = (00-1000) and ± 10 fr J > 1000. 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
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 = 3000 3 b e (6) 303
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 ± = 0.8194 10-8 / 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 11.876 9.43 11.133 10.164 10.089 9.713 10.467 9.795 9.7831 10.578 8.977 10.101 9.3179 10.14 8.6835 10.905 7.9090 10.507 8.4040 10.436 7.870 11.45 7.1753 10.856 7.6485 10.71 7.1797 11.53 6.6313 11.054 6.991 10.985 6.5848 11.785 6.1905 11.344 6.4901 11.0 6.0756 1.10 5.8374 11.584 6.0098 11.431 5.6683 1.41 5.4480 11.895 5.6094 11.641 5.638 1.589 * 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 ) 19.70 ± 0.45797 0.657 ± 0.41641 3.476 ± 0.4666 J K A a (Ǻ) σ Λ 513.7 48.1 5.963 0.011 56.0 177.8 5.363 0.051 47.7 4175.7 4.613 0.07 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 48.1 114.599 18.617 177.8 151.463 13.378 4175.7 54.196 1.47.98.67.79 TABLE:IV. Calculatin f the radii f the ins fr Acetylthichline salts in n-butanl at 5 C salts Λ (1) 19.694 0.637 3.437 - () λ η - λ (1) + (1) λ + (1) Av. λ R + (Ǻ) R - (Ǻ) 0.1307 8.3 11.464 3.8456 0.419 9.3 11.317 11.666.713 3.396 0.9048 11. 1.17 ±0.365.808 (1) hm -1 equiv -1 cm () hm -1 equiv -1 cm p R + +R - 6.559 6.109 5.534 a (Ǻ) 5.963 5.363 4.613 304
a 0 6 5.5 5 4.5 4 900 700 Ac.Th ClO4 900 700 500 500 300 300 J 100 100 J 1900 1900 1700 1700 4.5 5 5.5 6 6.5 7 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, 878-881 (009). [4] A.I. Kawana, M.T. Mhamed and N.H. El-Hammamy, J. Indian Chem. Sc., 84, 816-819 (007). [5] N.H. El-Hammamy, A,I.Kawana, Sh.A. El-shazly and F.F. El-bardisy, Bull. Electrchem., 10. 307 (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