Conformational analysis and interpretation of ν(OH) bands in the IR spectrum of o-vinylphenol: a DFT study

Two-dimensional cyclic potential energy surface for internal rotation of vinyl and hydroxyl substituents in o-vinylphenol molecule was constructed by the B3LYP/6-311G(d) method. It was shown that o-vinylphenol molecule exists in the gas phase as a mixture of seven rotamers denoted as A (A') B (B'), C (C') and D. The B3LYP/cc-pVTZ calculated percentage of the rotamers A and A' in which OH center dot center dot center dot pi intramolecular interaction occurs, is at most 24%. The height of barriers to interconversions between o-vinylphenol rotamers varies from 0.1 to 5.2 kcal mol(-1). According to B3LYP/cc-p VTZ calculations, the inclusion of solvent effect in the framework of the polarizable continuum model for a solution of o-vinylphenol in CCl4 leads to a decrease in theoretical values of nu(OH) frequencies by about 4-9 cm(-1) and to an increase in the percentage of the rotamers without intramolecular hydrogen bond by about 4.3% compared to the corresponding gas-phase values. The simulated IR spectral contours of nu(OH) bands are in good agreement with experimental ones.