Application of mass spectrometry to the study of prototropic equilibria in 5-substituted tetrazoles in the gas phase; experimental evidence and theoretical considerations

The tautomerism of tetrazole, 5-methyltetrazole, and its isotopically substituted derivatives is discussed on the basis of their fragmentation patterns, and of quantum chemical calculations by the LCAO MO method in the CNDO/2 approximation. The equilibrium of these compounds in the gas phase is displaced towards the 2H-tautomer. Analysis of the mass spectra of 5-methyl[2H3]tetrazole revealed randomization of hydrogen between the methyl and the NH groups.