NUCLEAR MAGNETIC RESONANCE STUDIES OF PROTON-EXCHANGE KINETICS OF N-METHYLACETAMIDE AND N-ACETYLGLYCINE N-METHYLAMIDE

Proton-exchange kinetics of compounds with peptide-like bonds, N-methylacetamide (NMA) and N-acetylglycine N-methylamide (AGMA), have been studied by the nmr method. NMA has one proton capable of exchanging, while AGMA has two. For AGMA, CH3CONHCH2CONHCH3, the amino proton adjacent to the methylene group is labeled site A, while the amino proton adjacent to the N-methyl group is labeled site B. The specific rate of protolysis of NMA is proportional to hydrogen ion concentration, while there is a 1.3-1.4 power dependence of the specific rate on hydrogen ion concentration for both sites A and B of AGMA. The activation energies of protolysis for NMA and AGMA sites A and B were found to be 16.4,16.2, and 17.7 kcal/mol, respectively.