Kinetics and Mechanism of the Anilinolysis of Dipropyl Chlorophosphate in Acetonitrile
作者:Md. Ehtesham Ul Hoque、Hai-Whang Lee
DOI:10.5012/bkcs.2012.33.6.1879
日期:2012.6.20
The kinetic studies on the reactions of dipropyl chlorophosphate (3O) with substituted anilines ($XC_6H_4NH_2$) and deuterated anilines ($XC_6H_4ND_2$) have been carried out in acetonitrile at $55.0^\circ}C$. The obtained deuterium kinetic isotope effects (DKIEs; $k_H/k_D$) are primary normal ($k_H/k_D$ = 1.09-1.01) with the strongly basic anilines while secondary inverse ($k_H/k_D$ = 0.74-0.82) with the weakly basic anilines. The steric effects of the two ligands on the rates are extensively discussed for the anilinolyses of the ($R_1O$)($R_2O$)P(=O or S)Cl-type chlorophosphates and chlorothiophosphates. A concerted mechanism is proposed with a frontside nucleophilic attack involving a hydrogen-bonded four-center-type transition state for the strongly basic anilines and with a backside attack transition state for the weakly basic anilines on the basis of the DKIEs, primary normal and secondary inverse with the strongly and weakly basic anilines, respectively.
已在55.0°C的乙腈中对氯二丙基磷酸酯(3O)与取代苯胺($XC_6H_4NH_2$)和氘代苯胺($XC_6H_4ND_2$)的反应进行了动力学研究。获得的氘动力学同位素效应(DKIEs;$k_H/k_D$)对于强碱性苯胺为主要正常型($k_H/k_D$ = 1.09-1.01),而对于弱碱性苯胺则为次要反向型($k_H/k_D$ = 0.74-0.82)。对这两种配体在($R_1O$)($R_2O$)P(=O或S)Cl型氯磷酸酯和氯硫磷酸酯的苯胺解反应速率的立体效应进行了广泛讨论。根据DKIEs,提出了一种协同机制,强碱性苯胺涉及前侧亲核攻击,形成一个氢键结合的四中心型过渡态,而弱碱性苯胺则通过后侧攻击形成过渡态,这与强碱性和弱碱性苯胺的主要正常与次要反向DKIEs一致。