Mechanism and Linear Free Energy Relationships in Michael-Type Addition of 4-Substituted Anilines to Activated Olefin in Acetonitrile

• Published in: International journal of chemical kinetics Vol. 45; no. 12; pp. 763 - 770
• Main Authors: Dhahri, N., Boubaker, T., Goumont, R.
• Format: Journal Article
• Language: English
• Published: Hoboken Blackwell Publishing Ltd 01-12-2013; Wiley Subscription Services, Inc
• Subjects: Kinetics
• ISSN: 0538-8066; 1097-4601
• DOI: 10.1002/kin.20811

ABSTRACT
Kinetic studies for the Michael‐type reactions of ethyl‐3‐(4′‐N,N‐dimethylaminophenyl)‐2‐(nonafluorobutane)sulfonylpro‐penoate 1 with 4‐X‐substituted anilines 2a–e (X = OCH3, CH3, H, F, and Cl) have been investigated in acetonitrile at 20°C. A quadratic dependence of the pseudo–first‐order rate constants (kobsd) versus [2a–e] has been observed and has been interpreted in terms of a dimer nucleophile mechanism. The finding of a relatively large negative ρ value (−3.09) for the Hammett plot suggests that the intermediate (I±) is highly zwitterionic in nature. A linear correlation (r2 = 0.9989) between the Hammett's substituent constants σ and nucleophilicity parameters N of 4‐X‐substituted anilines in acetonitrile has been observed. The electrophilicity parameters E of the olefin 1 is evaluated, using the correlations σ versus N and log k versus σ and compared with the electrophilicities of analogously Michael acceptors.