Conformational structure of divinylacetylene

Ab initio quantum chemical calculations of the divinylacetylene molecule wi th different mutual orientations of vinyl groups are carried out using the 6-31G*/MP2 basis set. The torsional potential is approximated by a Fourier series. It is shown that the second term of the series dominates. The entha lpies of the cis- and trans-isomers are nearly equal; the maximum correspon ds to the gosh-orientation (180.4 cm(-1) with respect to the cis-form). The vibrational spectra of the compounds with cis-, gosh-, and trans-orientati ons of vinyl groups are analyzed based on the ab initio calculations. It is concluded that the experimental data available in the literature agree wit h the hypothesis that divinylacetylene exists as cis- and trans-isomers.