Kinetic Study on the Reactions of (Diethylamino)dialkylphosphine with Ethylene Carbonate

Abstract

The rates of the reaction of (diethylamino)dialkylphosphine with ethylene carbonate have been determined by measuring with IR spectra the decrease in the amount of ethylene carbonate. The rates varies according to the class of the alkyl substituents on the phosphorus atom, i. e., the order of the rate was as follows:
Secondary alkyl>Primary alkyl>Methyl
Good correlations with Taft equation were found in each class of the alkyl substituents, and the p was found to be positive. The results are consistent with a mechanism involving a four-centered transition state where the phosphorus atom acts as an electrophile site and accepts the electron pair from the ester-oxygen atom of ethylene carbonate. In addition, the electrophilicity. of the phosphorus atom is affected considerably by the hyperconjugation effect of the substituents on the phosphorus atom.