Relative acidity and basicity of amines in tetrahydrofuran and the influence of these factors on the carbonylation of lithium amides

Abstract

The equilibrium constants for the ion-pair formation between 2,4-dinitrophenol and the following amines: pyrrolidine, piperidine, dibutylamine, di-isopropylamine, cyclohexylisopropylamine, dicyclohexylamine, morpholine, and diethylamine, in tetrahydrofuran (THF) have been measured. The relative acidities of the same amines (except diethylamine) have been also determined, as well as the pK_a-values for di-isopropylamine, cyclohexylisopropylamine, and dicyclohexylamine in THF. The results show the importance of acid–base equilibria in determining the product distribution in the carbonylation of lithium amides in THF. They also explain the role of the [amine] : [amide] ratio in determining the reaction products.