ABINITIO STUDY OF THE STRUCTURE, IN-PLANE HARMONIC FORCE-FIELD, AND FUNDAMENTAL VIBRATION FREQUENCIES OF CIS-ACROLEIN AND TRANS-ACROLEIN

The structure, in-plane force field, and fundamental vibration frequencies of trans- and cis-acrolein are computed ab initio using 4-31G and (7,3) basis sets. Using a scaling procedure and spectroscopic masses, the vibration frequencies are calculated from ab initio force constant matrices, and found on average to be within 2.5% of the experimental values in the case of the trans conformer. The values predicted for the cis conformer, for which only a few tentative assignments have been made for spectroscopic observations, should facilitate the complete assignment in the future. Further experimental studies are necessary to resolve the substantial disagreement found between theory and experiment with respect to the length of the central formal carbon-carbon single bond in the series of molecules trans-glyoxal, trans-acrolein, and trans-1,3-butadiene. © 1979.