Thermodynamic properties of organic oxygen compounds. Part XXIII. Low-temperature heat capacity and entropy of C6, C7, and C9 ketones

Abstract

The heat capacities of five ketones [hexan-2-one (I), hexane-3-one (II), 3,3-dimethylbutan-2-one (III), 2,4-dimethylpentan-3-one (IV), and nonan-5-one (V)] have been measured. Triple-point temperatures, heats of fusion, and purities of the samples were determined. Compounds (II) and (V) were found to exist in two crystalline forms, the transitions from lower to higher temperature forms resulting in entropy increments of 4·73 and 3·39 J/K mol respectively. The entropies of the liquid ketones at 298·15 K are: (I), 308·1; (II), 305·3; (III), 282·4; (IV), 318·0; and (V), 401·4 J/K mol. The entropy of (II) at 298·15 K in the ideal-gas state was found to be 409·6 J/K mol.