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Aminolysis of Phenyl-Substituted p-Chlorophenyl Chlorothiophosphates in Acetonitrile

등록일
2005년 8월 11일 12시 10분 35초
접수번호
0813
발표코드
22P106포 이곳을 클릭하시면 발표코드에 대한 설명을 보실 수 있습니다.
발표시간
토 <발표Ⅳ>
발표형식
포스터
발표분야
물리화학
저자 및
공동저자
M. E. Hoque, 김찬경, 이본수, 이해황
인하대학교,
The kinetics and mechanism of the aminolysis of aryl p-chlorophenyl chlorothiophos phates, (p-ClC6H4O)P(=S)(Cl)OC6H4Y; 1, are investigated in acetonitrile at 550C. The obtained cross-interaction constant are both negative, ƒÏXY= -0.41 and -0.40, suggesting that the reaction proceeds by an SN2 mechanism. The Hammett plots of ( logk2 vs  ƒÐY)  show a sharp break at ƒÐY =0, suggesting changes in the TS structure to a more associative type.The primary kinetic isotope effects (kH/kD = 1.10 −1.46)observed.Theƒ¢H¹‚ (4.2−10.9 kcal mol-1) and ∆S¹‚ (-48 − -61 cal mol-1K-1) values are obtained.The rates are much slower than the corresponding reactions of (p-ClC6H4O)P(=O)(Cl)OC6H4Y; 2, due to lower electrophilicity of P in P=S relative to P=O, because of electronegativity differences. The rates are faster than those for the corresponding reactions of (C6H5O)P(=S)(Cl)OC6H4Y; 3, due to the presence of electron withdrawing group, p-Cl in the benzene ring in 1.The selectivity parameters ƒÐY (0.10 −0.70, 0.70-1.06),  ƒÏx (-3.53 − -3.92), ƒÀx(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 forming and bond breaking are extensive.

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