The conformation and vibrational spectra of 1,5-hexadiene-3-yne (divinylacetylene) and perchloro-1,5-hexadiene-3-yne (perchlorodivinylacetylene)

Infrared spectra of 1,5-hexadiene-S-yne (divinylacetylene) have been recorded in the vapour phase, in solution and in the amorphous and crystalline solid states at 90 K in the region 4000–4020 cm^?1. Correspondingly, IR spectra ofperchloro-1,5-hexadiene-3-yne (perchlorodivinylacetylene) as a melt, as a solute in various solvents and as a solid at 90 K have been obtained. Raman spectra of the two compounds were recorded in the liquid (molten) state including polarization measurements, and as crystalline solids at 90 K.The spectral data indicate that each compound exists as one conformer only in the various states of aggregation. In divinylacetylene the molecular symmetry appears to be anti (C_2h) while for perchlorodivinylacetylene the symmetry is either C_2v (syn) or C₂ (gauche). Vibrational assignments for the spectra of both molecules are presented and the values are compared with the results of normal coordinate analyses.