Electrophilicities of 1,2-Disubstituted Ethylenes.

The kinetics of the reactions of maleic anhydride, N-methylmaleimide, fumaronitrile, diethyl fumarate, and diethyl maleate with pyridinium and sulfonium ylides were studied in DMSO at 20 °C. All of the reactions were found to follow a second-order rate law, and can be described by the linear free energy relationship log k2 (20 °C) = sN( N + E), where N and sN are solvent-dependent nucleophile-specific parameters, and E is an electrophile-specific parameter. The electrophilicity parameters E of the investigated acceptor-substituted alkenes were derived from the linear correlations of (log k2)/ sN vs. N, and range from -19.8 to -11.1. [ABSTRACT FROM AUTHOR]