Vibrational spectra and normal coordinate analysis for trans-2-butene-d and trans-2-butene-d8

The vibrational spectra of trans-2-butene-d0 and trans-2-butene-d8 were recorded in the region 4000–100 cm–1. In conjunction with a normal coordinate analysis, vibrational assignments are proposed on the basis of Raman depolarization ratios for the liquid samples, isotopic shift ratios, and group coordinate considerations. Both assignments and vibrational coupling effects are discussed in terms of the calculated potential energy distributions. A 21-parameter modified internal valence force field was determined by least squares procedures from the observed polycrystalline frequencies of the two isotopic species.