Collect. Czech. Chem. Commun. 1982, 47, 35-44

The confirmation of trisubstituted ureas and thioureas in solution

Jaromír Kaváleka, Pavel Fiedlerb, Zlata Papouškovác and Otto Exnerb

a Department of Organic Chemistry, Institute of Chemical Technology, 532 10 Pardubice
b Institute of Organic Chemistry and Biochemistry, Czechoslovak Academy of Sciences, 166 10 Prague 6
c Institute of Chemical Process Fundamentals, Czechoslovak Academy of Sciences, 165 02 Prague 6 - Suchdol


Dipole moments of 1,1-dimethyl-3-arylureas Ia-Ie, measured in benzene and dioxan solutions, were interpreted in terms of the Z-conformation (A), taking into account a proper correction for the conjugation within the functional group. The conformation was corroborated on the basis of infrared spectra in several solvents, in particular referring to the amide-II band. No indication of any minor conformer was obtained. The same techniques applied to 1,1-dimethyl-3-arylthioureas IIa. IIb confirmed the already reported equilibrium of Z- and E-conformers; their population depends sensitively on solvent.