Rotational isomerism of vinyl ethers of azines based on the data of IR spectroscopy and quantum-chemical AM1 calculations

The IR spectra of vinyl ether; of azines have two C=C stretching vibration bands of the vinyl group at 1620 and 1640 cm(-1), which correspond to the s -cis and nonplanar s-trans conformers, respectively. According to the resul ts of AM1 calculations, the hetaryl fragment and the vinyl group in the s-t rans conformers of all the ethers under study are twisted out of the C-O-C plane by similar to 30 degrees. In the s-cis conformation, the angle of rot ation of the heterocycle with respect to the vinyloxy group varies from 45 to 90 degrees. The character of the change in the intensity of the nu(C=C) absorption bands of the doublet under changes of the temperature indicates that the s-trans conformer is energetically favorable. The exception is 5-v inyloxyacridine for which the s-cis conformation is more favorable.