A DIPOLE MOMENT STUDY OF N-METHYL AND N,N'-DIMETHYL-IMIDAZOLIDIN-2-ONES, IMIDAZOLIDINE-2-THIONES AND -2-SELENONES

Article abstract of DOI:10.1016/0022-2860(81)80068-3

The electric dipole moments in benzene and dioxan of potentially tautomerizable N-methylimidazolidin-2-one, N-methylimidazolidine-2-thione and -2-selenone clearly support the lactam structure for these compounds.The fact that their dipole moments in dioxan are markedly greater than those in benzene is explained by a higher (HN-C=Y) mesomeric moment in the hydrogen-bonded solute...dioxan complexes.Analysis of the dipole moments in benzene of N,N'-dimethylimidazolidin-2-one, N,N'dimethylimidazolidine-2-thione and -2-selenone shows that the mesomeric moment (due to contribution of ⁺N=C-Y^- zwitterionic valence structures) gradually increases on going from Y=O to Y=S, and Y=Se.Finally, preferred conformations, from their dipole moments in benzene, are suggested for tetramethylurea and tetramethylthiourea.