The hydrophobic effect in aqueous solutions of positional isomers of alkan-n-ols. A calorimetric study at 298.15 K

Enthalpies of dilution were measured for binary aqueous solutions of positional isomers of pentanol and hexanol, and for some ternary solutions containing two of the following alcohols: methanol, ethanol, propan-1-ol, butan-1-ol, and pentan-1-ol. The enthalpic interaction coefficients found depend greatly on the alkyl chain length and on the position of the hydroxyl functional groups. A refinement of the model of overlapping hydration cospheres is proposed. Two hydrated molecules should interact through a preferential, "side on", orientation, stabilized by the contemporaneous juxtaposition of the hydroxyl groups and the alkyl chains. The effects which cause the hxx values of positional isomers to differ are discussed. © 1991.