On the Reorientation and Hydrogen-Bond Dynamics of Alcohols.

The mechanism of the OH bond reorientation in liquid methanol and ethanol is examined. It is found that the extended jump model, recently developed for water, describes the OH reorientation in these liquids. The slower reorientational dynamics in these alcohols compared to water can be explained by two key factors. The alkyl groups on the alcohol molecules exclude potential partners for hydrogen bonding exchanges, an effect that grows with the size of the alkyl chain. This increases the importance of the reorientation of intact hydrogen bonds, which also slows with increasing size of the alcohol and becomes the dominant reorientation pathway.