Dipole moments and molecular conformations of O-vinyl- and O-ethylacetoximes in solutions

Dipole moments of the molecules of O-vinyl- and O-ethylacetoximes in octane and THF were measured at different temperatures. In octane, the equilibriu m mixture of stable O-vinylacetoxime conformers consists of forms with diff erent polarity. Polarity of these conformers, which are due to rotation abo ut the C-O and N-O bonds, is mainly determined by the relative position of the lone electron pairs of nitrogen and oxygen atoms. The fraction of the p olar conformer increases, as temperature increases, as well as on going fro m octane to THF. Saturation of the vinyl group in the O-vinylacetoxime mole cule nearly halves the molecular dipole moment in the nonpolar medium, whic h radically differentiates this compound from vinyl ethers.