The Conformation of Alkyl Benzyl Alcohols Studied by ab initio MO Calculations − A Comparison with IR and NMR Spectroscopic Data

Ab initio MO calculations were carried out for the conformations of a series of alkyl‐substituted benzyl alcohols C 6 H 5 CH 2 CHOH−R (R = CH 3 , C 2 H 5 , i Pr, t Bu) at the MP2/6‐311G(d,p)//MP2/6‐31G(d) level. It was found that the conformation where the OH group is gauche to the phenyl group is the most stable. The geometry where both the OH and R groups are close to phenyl is the second most stable. This finding has been interpreted on the grounds of the attractive OH/π and CH/π hydrogen bonds and a repulsive van der Waals interaction between vicinal CH groups. NMR nuclear Overhauser effects, spin‐coupling data, and IR spectroscopic data are consistent with the conclusion given by the MO calculations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)