HYDROGEN-BONDING - PART 45 - THE SOLUBILITY OF GASES AND VAPORS IN METHANOL AT 298 K - AN LFER ANALYSIS

Values of the Ostwald solubility coefficient of gases and vapours in m ethanol solvent, L-MeOH, at 298 K have been determined for 23 solutes by an indirect method in which experimental partition coefficients bet ween methanol and hexadecane were combined with literature data on Ost wald solubility coefficients in hexadecane. Another 70 L-MeOH values w ere obtained from literature data and the total 93 values were correla ted by the Abraham equation to give the regression, where n = 93, r(2) = 0.9952, sd = 0.13 and F = 3681. log L-MeOH = -0.004 - 0.215 R-2 + 1 .173 pi(2)(H) + 3.701 Sigma alpha(2)(H) + 1.432 Sigma beta(2)(H) + 0.7 69 log L-16 The solute descriptors In eqn. (i) are: R-2 an excess mola r refraction, pi(2)(H) the dipolarity/polarisability, Sigma alpha(2)(H ) the overall hydrogen-bond acidity Sigma beta(2)(H) the overall hydro gen-bond basicity and log L-16, where L-16 is the Ostwald solubility c oefficient on hexadecane at 298 K, The number of data points, or solut es, is n, the correlation coefficient is r, the standard deviation is sd and Fis the F-statistic, Just as for the case of water solvent, sol ute dipolarity/polarisability, hydrogen-bond acidity and hydrogen-bond basicity all lead to an increase in log L, although methanol is much less acidic than water. However, contrary to the solubility of vapours in water, the log L-16 descriptor now also leads to an increase in lo g L, Explanations for the different behaviour of water and methanol ar e given. An analysis of log P values for the transfer of solutes from water to methanol also shows that bulk methanol is as strong a hydroge n-bond base as bulk water but is a much weaker hydrogen-bond acid.