Volumes and heat capacities of benzene derivatives in water at 25°C: Group additivity of the standard partial molal quantities

Abstract

Differences in densities and heat capacities per unit volume were measured in water with a flow densimeter and a flow microcalorimeter for a series of substituted benzene compounds in water at 25°C. Apparent molal volumes and heat capacities were calculated from the data, and, by extrapolation to infinite dilution, the standard partial molal quantities were dervied. An additivity scheme is proposed to obtain the group contribution to these systems. The standard partial molal volumes and heat capacities of rather complex aromatic molecules in water can be predicted inside about 1 cm3 mol−1 and 10 J K−1 mol−1. The values of the volumes and heat capacities of groups adjacent to an aromatic ring are not the same as those on an aliphatic molecule but a simple relation exists between both sets.