Kinetics and Mechanism of the Reaction of para-Chlorophenyl Aryl Chlorothiophsphates with Anilines in Acetonitrile at 55℃`.

초록

Md. Ehtesham UI Hoque, Chan Kyung Kim, Bon-Su Lee, Hai Whang Lee Department of Chemistry, Inha University The Kinetics and mechanism of the aminolysis of para-chlorophenyl arly chlorothiophsphates, (p-CIC6H4OP(=S)(CI)OC6H4Y) 1, are inverstigated in acetonitrile at 55℃. The obtained cross-interaction constants are both negative, pxy = -0.29 and pxy = -1.07, suggesting that the reactions proceed by SN2 mechanism. The Hammett plots (logk2 vs. δy) show a sharp break at δy = 0. The activation parameters △H≠(4.2 - 11.5 kcal mol-1) and △S≠(-47 - -61cal mol-1 k-1) values are corresponding reactions of para-chlorophenyl aryl chlorothiophsphates (p-CIC6H4OP(=S)(CI)OC6H4Y) 2, due to lower electrophilicity of P in P=S relative to P=O, because of electrophilicity differnces, favoring O over S. The rates are faster than those for the corresponding reaction of aryl phenyl chlorothiophosphates, (C6H5OP(=S)(CI)OC6H4Y) 3, due to the presence of electron withdrawing group, p-CI in the benzene ring in 1. The selectivity parameters, px ( = -3.35 - -3.86) βx( = 1.24 - 1.36) and two distinct group of py (0.13 - 0.61 for δy < 0 ) and (0.22 - 0.60 for δy > 0) values of 1 are similare to 3, suggesting similar mechanism of 3, a concerted process with a late, product-like transition state in which both the bond marking and leaving group departure are extensive.