Nucleophilic substitution reactions of Y-aryl methyl (8) and Y-aryl propyl (10) chlorothiophosphates with substituted anilines and deuterated anilines are investigated kinetically in acetonitrile at $55.0^\circ}C$. A concerted mechanism is proposed for 8 based on the negative $\rho}_XY}$ (= -0.23) value, while a stepwise mechanism with a rate-limiting leaving group departure from the intermediate is proposed for 10 based on the positive $\rho}_XY}$ (= +0.68) value. The deuterium kinetic isotope effects (DKIEs; $k_H/k_D$) are 0.89-1.28 and 0.62-1.20 with 8 and 10, respectively. Primary normal and secondary inverse DKIEs are rationalized by a frontside attack involving hydrogen bonded, four-center-type transition state and backside attack involving in-line-type transition state, respectively.
在
乙腈中于
$55.0^\circ}C$下,研究了Y-芳基
甲基(8)和Y-芳基丙基(10)
氯硫磷酸盐与取代
苯胺和
氘代苯胺的亲核取代反应动力学。基于负值的
$\rho}_XY}$(=-0.23),为8提出了协同机理,而基于正值的
$\rho}_XY}$(=+0.68),为10提出了带有速率限制
中间体离去基团的分步机理。
氘的同位素效应(DKIEs;
$k_H/k_D$)分别为8的0.89-1.28和10的0.62-1.20。通过涉及
氢键的四中心型过渡态的前侧攻击和涉及直线型过渡态的后侧攻击,分别合理化了初级正常和次级反向的DKIEs。