Electrophilicity Parameters for Benzylidenemalononitriles

Kinetics of the reactions of stabilized carbanions (derived from nitroethane, diethyl malonate, ethyl cyanoacetate, ethyl acetoacetate, acetyl acetone) with benzylidenemalononitriles have been determined in dimethyl sulfoxide solution at 20 degrees C. The second-order rate constants are employed to determine the electrophilicity parameters E of the benzylidenemalononitriles according to the correlation equation log k (20 degrees C) = s(E + N). Comparison with literature data shows that this equation allows the semiquantitative prediction of the reactivities of benzylidenemalononitriles toward a wide variety of nucleophiles, including carbanions, enamines, amines, water, and hydroxide.