Heat of solution in water of the liquid methylene group at 25°C

The heats of solution of some liquid n-carboxylic acids and n-alkanols to high dilution in water at 25°C have been determined calorimetrically. From these and already published data, for a series of n-alkylhexaoxyethylene glycol monoethers, it is concluded that the heat of solution of the liquid —CH2— group in water for the systems studied is about +350 cal/mole up to alkyl chain lengths of C8, if polar head group effects are not operative. There is no evidence that above C8 the —CH2— increment in the heat of solution of n-alkyl chain compounds is constant. The usefulness of alkane/water interfacial tension data in estimating the thermodynamic parameters of transfer of the methylene group is discussed.