Infrared spectra of diphenylethine and diphenylethine-d10

Abstract

The infrared spectra of diphenylethine and diphenylethine-d10 have been measured in the 4000–33 cm−1 region both for solution and solid samples. Polarized spectra of oriented crystals, (001) crystal plane, allow segregation of most bands into their respective symmetry classes. The slightness of correlation crystal field effects suggested by the comparison between crystal and solution spectra is confirmed by measurements on dilute isotopic solutions. The oriented gas model predictions are a useful guide despite some well-identified deviations.The assignment of the infrared active fundamentals is proposed on the basis of the dichroic indications and the isotopic shifts. Most of the relevant absorption frequencies of diphenylethine and diphenylethine-d10 are recognized as characteristic of a monosubstituted benzene and the spectra are interpretable on the basis of two phenyl groups weakly interacting through the acetylenic bridge.