Brönsted exponents in the proton abstraction from derivatives of ethyl α-benzylacetoacetate, 3-benzylpentane-2,4-dione, and benzylmalononitrile

Abstract

Measurements are reported of the rates of proton transfer from ring-substituted ethyl α-benzylacetoacetates, 3-benzylpentane-2,4-diones, and benzylmalononitriles to a series of carboxylate ions. For the first two series the Brönsted exponents for substitution in the carbon acid are considerably greater than those for substitution in the carboxylate ion, and this behaviour is compared with the more extreme differences previously reported for reactions of the nitro-alkanes. For the benzylmalononitriles both exponents are equal to unity. Velocity constants are also given for the reactions of 3-benzylpentane-2,4-diones with water and with pyridine, and of benzylmalononitriles with water.