General-base-catalysed proton exchange in 1,3-dimethyl-2-iminoimidazolidin-4-one hydriodide

Abstract

The general-base-catalysed exchange of the methylene protons of the title compound in D₂O has been studied using n.m.r. techniques with 70 bases that include aliphatic monocarboxylates and dicarboxylates, o-, m-, and p-substituted benzoates, 2-, 3-, and 4-substituted pyridines, creatinine, and D₂O. Aliphatic monocarboxylates, m- and p-substituted benzoates, the pyridines, and D₂O conform to a single Brønsted relationship (β 0.79 ± 0.05). However, o-substituted benzoates exhibit enhanced catalytic activity while the aliphatic dicarboxylates and creatinine show reduced catalytic activity. The possible causes for such deviations are discussed.