Analysis of hydrogen-bond complexation constants in 1,1,1-trichloroethane: the α2Hβ2H relationship

Abstract

Hydrogen-bond complexation constants determined by Taylor and co-workers using 1,1,1-trichloroethane (TCE) solvent have been analysed through the α₂^Hβ₂^H relationship; α₂^H and β₂^H are the solute hydrogen-bond acidity and basicity parameters obtained from complexation constants in tetrachloromethane. Constants for three alcohol/N-methylpyrrolidinone complexations have been determined in TCE, and if these are used instead of the original alcohol/N-methylpyrrolidinone complexation constants, a good relationship is obtained, eqn. (i). The slope in eqn. (i) is smaller than that for the α₂^Hβ₂^H relationship in tetrachloromethane, but the intercept is the same.

Eqn. (i) has been used to obtain 25 new α₂^H values for acids; these include acetanilides, sulfonamides, triazoles and tetrazoles. The latter two types of compound have very large α₂^H values; that for 5-phenyl-1,2,3,4-tetrazole (0.88) being near the value for dichloroacetic acid (0.90). Values of β₂^H for 31 hydrogen-bond bases have also been calculated using eqn. (i). These include bases with heterocyclic moieties to which β₂^H values had not previously been assigned, e.g. oxazole, isoxazole, triazoles and a tetrazole.