An empirical potential function for cyclopropene and vibrational spectra of cyclopropene-1,3-d2

Abstract

A potential function has been fitted to the vibrational fundamentals of eight of the nine possible hydrogen-deuterium isotopomers of cyclopropene. For one of these species, the 1,3-d/sub 2/molecule, infrared and Raman spectra are reported for the first time and assigned. The fundamental frequencies (in cm/sup -1/) of the 1,3-d/sub 2/ species are 3134, 2972, 2384, 2203, 1598, 1348, 1104, 1020, 979, 903, (821), 771, 749, 657, and 475. The value in parentheses is in doubt. The new empirical potential function is a significant improvement over the earlier one of Wiberg and Wendoloski, which came from fitting only the frequencies of the four isotopomers of C/sub 2v/ symmetry. The empirical potential function is discussed in relationship to the later semiempirical potential function of Wiberg, Dempsey, and Wendoloski, which was obtained by fitting the diagonal force constants to observed frequencies while using scaled, ab initio values of the off-diagonal force constants. Accurate frequencies are predicted for the as-yet unknown 1,2,3-d/sub 3/ isotopic species.