A Mechanistic Study on Acyl Transfer Reactions of Aryl Substituted Benzoates Between Aryloxides

• Published in: Bulletin of the Korean Chemical Society 1991, Vol.12 (4), p.406-410
• Main Authors: Ik-Hwan Um, Jae-Shin Jeon, Dong-Sook Kwon
• Format: Article
• Language: Korean
• ISSN: 0253-2964; 1229-5949

Second order rate constants have been measured spectrophotometrically for reactions of 4-nitrophenyl substituted benzoates with various aryloxides and aryl benzoates with p-chlorophenoxide. The reactivity has exhibited significant dependences on the electronic nature of the substituent in the acyl moiety of the substrate and in the nucleophilic phenoxide, while the substituent in the leaving phenoxide has little influenced the reactivity. The Bronsted coefficient $\beta$ values so obtiained support that the present acyl transfer reaction proceeds via a stepwise mechanism in which the nucleophilic attack would be the rate-determining step. Interestingly, the magnitude of the $\betaacyl$ and $\beta$ nuc increases with increasing reactivity, implying that the reactivity selectivity principle is not operative in the present system. The failure of the reactivity selectivity principle is attributed to a change in transition state structure upon the substituent variation in the present acyl transfer reaction.