Intermolecular methyl transfer on pyrolysis of carpronium chloride

Abstract

The methyl transfer occurring in the production of methyl N,N‐dimethyl‐γ‐aminobutyrate by pyrolysis of carpronium chloride was examined by means of pyrolysis gas chromatography mass spectrometry with the aid of some deuterated compounds. The mass spectra of methyl N,N‐dimethyl‐γ‐aminobutyrate, produced from deuterated derivatives of carpronium chloride, showed inter alia, characteristic molecular ion peaks which indicated that the methyl of the trimethylammonium group transfers and displaces the methyl of the carbomethoxy group of the tertiary amino compound. The results show that an intermolecular methyl transfer occurs in part on pyrolysis of carpronium chloride, to form methyl N,N‐dimethyl‐γ‐aminobutyrate in which the methyl oxygen is replaced by a methyl from the nitrogen of the original compound. The mechanism presented involves the bimolecular reaction between zwitterionic intermediates formed by ionic O‐demethylation of carpronium chloride.