Mass Spectral Study of the Occurrence of Tautomeric Forms of Thiohydantoins

Abstract

Mass spectrometry is used to evaluate the occurrence of thio-enol structures among the several possible tautomers of thiohydantoins and dithiohydantoins. Mass spectra of differently-substituted thiohydantoins are examined looking for common mass spectral behaviors to be predicted. Ion fragmentations from specific tautomers allow the most stable thio-enol structure for both type of compounds. The mass spectrum of the alkylation product of 5,5-dimethyldithiohydantoin and the nuclear magnetic resonance spectra of the alkylation products of both 2-thiohydantoin and dithiohydantoin support the fact that the most likely thio-enol structure is determined by the presence of one or two thio-carbonyl groups in the hydantoin molecule.