Collect. Czech. Chem. Commun. 1982, 47, 814-827

Configuration and conformation of amidoximes. N,N-Dialkyl derivatives

Otto Exnera and Nedelko Motekovb

a Institute of Organic Chemistry and Biochemistry, Czechoslovak Academy of Sciences, 166 10 Prague 6, ČSSR
b Department of Inorganic Chemistry, Higher Institute of Food and Flavour Industries, 4000 Plovdiv, Bulgaria


Dipole moments of N,N-dialkylamidoximes Ia-Ie and of substituted O-benzoyl-N,N-dimethyl-benzamidoximes IIa-IIe were measured in benzene or dioxan, respectively. The results with the latter set of compounds allow to assign in an independent and unambiguous way the E-configuration which was found previously for all N,N-dialkylamidoximes investigated in the crystalline state; our reasoning does not involve bond moment values within the amidoxime functional group. The fundamental difference in the stereochemistry between unsubstituted amidoximes and their N,N-dialkyl derivatives has thus been confirmed. On the other hand, the configuration of simple N,N-dialkylamidoximes (e.g. Ia-Ie) cannot be deduced from their dipole moments in a straightforward manner. The reason is that the conjugation within the N=C-N chain requires a mesomeric correction term which cannot be neglected and is not equal in either configuration. The example shows very clearly limitations of the bond moment approach if applied to conjugated molecules.