THE EFFECT OF THE MOLECULAR SHAPE ON THE ENTHALPIC BEHAVIOR OF LIQUID-MIXTURES - CYCLIC HYDROCARBONS IN HEPTANE AND TETRACHLOROMETHANE

Excess enthalpies H-E at 298.15 K have been determined by flow microca lorimetry for binary mixtures of heptane or tetrachloromethane+a cycli c hydrocarbon (cycloheptane, cyclooctane, cyclodecane, 1,2,3,4-tetrahy dronaphthalene, cis-decahydronaphthalene, trans-decahydronaphthalene, bicyclohexyl). With the exception of tetrahydronaphthalene+tetrachloro methane and of trans-decahydronaphtalene+heptane, all mixtures examine d exhibit positive deviations. H(E)s have been analysed in terms of th e DISQUAC model. Partial molar excess enthalpies at infinite dilution as well as standard enthalpies of solvation, Delta H-0, have been eval uated for cycloalkanes in the two solvents and compared with those of linear and branched alkanes. The effect of cyclization upon Delta H-0 has been discussed and the contributions to Delta H-0 of the cavity an d of the interaction terms have been estimated through the scaled part icle theory.