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 degrees C. A quadratic dependence of the pseudo-first-order rate constants (k(obsd)) versus [2a-e] has been observed and has been interpreted in terms of a dimer nucleophile mechanism. The finding of a relatively large negative value (-3.09) for the Hammett plot suggests that the intermediate (I-+/-) is highly zwitterionic in nature. A linear correlation (r(2)= 0.9989) between the Hammett's substituent constants sigma 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 sigma versus N and log k versus sigma and compared with the electrophilicities of analogously Michael acceptors.