The temperature dependence of the νs(OH) frequency of self-associated methanol in solution

Abstract
The first moment M 1(H) of the v s(OH) absorption band of self-associated CD3OH in freon 11 and the corresponding first moment M 1(D) of self-associated CH3OD have been measured at 10 K intervals between 160 K and 280 K. The regression of the moments on coth (ħω2/2kT) is close to linear, with correlation coefficients of 0·998 for H and 0·999 for D. The ratio M 1(H)/M 1(D) is independent of temperature. The frequency shifts with temperature are much too great to be explicable solely in terms of thermal expansion of the hydrogen bond. We argue that a quartic anharmonic coupling between the νs(OH) and νσ(OH … O) modes is largely responsible for the effect.