[en] As a consequence of partial double bond nature of the exocyclic C-N bond, 2-methyl-amino-4-thiazolinone exists in DMSO-D₆ as a mixture of E and Z conformers of the amino form with predominance of the sterically favored E conformer. 2-Phenylimino-4-thiazolidinone in the same solvent exists as a mixture of the E and Z isomers of the imino form