Aminolysis of Phenyl-Substituted p-Chlorphenyl Chlorothiophosphates in Acetontrile

초록

The kinetics and mechanism of the aminoylsis of aryl p-chlrophenyl chlrothiphos phates, (p-CIC6H4O)P(=S)(CI)OC6H4Y; 1, are investigated in acetonitrili at 550C.The obtained cross-interaction constant are both negative, fiXY= -0.41 and -0.40, suggesting that the reaction proceeds by an SN2 mechanism. The Hammett plots of (logk2 vs fDY) show a sharp break at fDY =0, suggesting changes in the TS structure to a more associative type. The primary kinetic istope dffects (kH/kD = 1.10-1.46)observed. ThefcH1, (4.2-10.9 kcal mol-1) and △ㄴ1, (-48 - -61 cal mol-1) values are obtained. The rates are much slower than the corresponding reactions of (p-CIC6H4O)p(=O)(CI)OC6H4Y; 2, due to lower electrophilicity of P in P=S relative to P=O, because of electronegativity differnces. The rates are faster than those for the corresponding reactions of (C6H5O)P(=S)(CI)OC6H4Y; 3, due to the presence of (CH6C5O)(P)=(S)(CI)OC6H4Y; 3, due to the presence of electron withdrawing group, p-CI in the benzene ring in 1. The selectivity parameters fDY (0.10 -0.70, 0.70-1.06), Fix (-3.53 - -3.92), fAx(1.24 - 1.38) values of 1 are similar to 3, suggesting similar mechanism of 3, a concerted process with a late, product-like transition state in which bond formingand bond breaking are extensive.