Equilibrium reactions of n -butanethiol with some conjugated heteroenoid compounds

Abstract

The reactions of 2-benzal-1,3-indanediones and the cyano-containing benzalmalononitriles, ethyl benzalcyanoacetates, benzalcyanoacetamides, and benzalcyanoacetanilides with n-butanethiol at 25 °C in 20% ethanol – 80% pH 7 buffer attain equlibrium at a rate too fast to measure by standard methods. The equilibrium constants have been calculated and these in turn related to Hammett σ and Taft σ* constants. The differences in the reactions of these and other gem difunctional systems which react virtually completely with n-butanethiol under the same experimental conditions and at a measurable rate, are attributed to participation of the functional group cis to the phenyl group in the reverse reaction. It is shown that n-butanethiol adds to cinnamalacetophenone by a 1,4-mechanism and the reactions of this nucleophile with similar compounds having extended conjugated systems are discussed.