Kinetics of acid-catalyzed deuteriation of the 2,3-dihydro-5,7-dimethyl-1,4-diazepinium cation

Abstract

Rates of deuteriation at C-6 of 2,3-dihydro-5,7-dimethyl-1,4-diazepinium perchlorate, in phosphate-buffered deuterium oxide, were determined by ¹H n.m.r. spectroscopy. The rate was found to be independent of pH (from pH 6 to 8) and of the concentration of DPO₄^2– but directly proportional to the concentration of D₂PO₄^–. The reaction is one of the few electrophilic substitutions in which the electrophile donor is negatively charged and the acceptor is positively charged. It is thought that D₂PO₄^– is particularly effective, and D₃O⁺ particularly ineffective, because of attraction of unlike charges and repulsion of like charges, respectively.