Kinetics and Mechanism of the Anilinolysis of O-Ethyl Phenyl Phosphonochloridothioate in Acetonitrile

摘要

The nucleophilic substitution reactions of O-ethyl phenyl phosphonochloridothioate with substituted anilines (XC6H4NH2) and deuterated anilines (XC6H4ND2) are kinetically investigated in acetonitrile at 55.0 °C. The deuterium kinetic isotope effects (DKIEs) invariably increase from a secondary inverse DKIE (k_H/k_D = 0.93) to a primary normal DKIE (k_H/k_D = 1 -28) as the substituent of nucleophile (X) changes from electron-donating to electron-withdrawing. These can be rationalized by the gradual transition state (TS) variation from a backside to frontside attack. A concerted S_n2 mechanism is proposed. A trigonal bipyramidal TS is proposed for a backside attack while a hydrogen-bonded, four-center-type TS is proposed for a frontside attack.