Vibrational Spectroscopic and Conformational Analysis of Pinosylvin

Abstract

Infrared and Raman spectra of pinosylvin were recorded and the vibrational frequencies with the corresponding infrared intensities were compared with the results of ab initio calculations utilizing the DFT method with the Becke3P86 functional and the 6-31G(d) basis set. Normal coordinate analysis was carried out. The effect of the conformation of the OH groups on the distribution of net charges, molecular energy and vibrational fundamentals were analyzed. One of the OH-cis−OH-trans conformers has the lowest energy. The conformation has a strong effect on the aforementioned properties, e.g., the cis-to-trans transition generates electron repulsion toward the vinylidene group between the two benzene rings. The changes in the different properties are in good accordance with each other. For comparison, the vibrational spectra were also recorded and calculated for the parent compound, trans-stilbene.