EXCESS MOLAR HEAT-CAPACITIES AND EXCESS MOLAR VOLUMES OF BINARY-MIXTURES OF 2-BROMO-2-CHLORO-1,1,1-TRIFLUOROETHANE (HALOTHANE) WITH OXYGENATED AND HYDROCARBON SOLVENTS

Excess molar heat capacities C(p)E were determined at 298.15 K for the following thirteen mixtures: 2-bromo-2-chloro-1,1,1-trifluorethane (halothane)+acetone (ACT), +dipropyl ether (DPE), +diisopropyl ether (DIPE), +methyl tert-butyl ether (MTBE), +tetra-hydrofuran (THF), 1,4-dioxane (DIOX), +methyl acetate (MAC), +benzene (BENZ), +cyclohexane (cC6), +n-hexane (nC6), +2,2-dimethylbutane (22DMB), +n-heptane (nC7), and +2,4-dimethylpentane (24DMP). Excess molar volumes V(E) at 281.15 K were also measured for the following mixtures: halothane + DPE, +DIPE + DIOX, +BENZ, +cC6, +22DMB, +nC7, and +24DMP. V(E) values for the remaining five mixtures (ACT, MTBE, THF, MAC, and nC6) were previously reported. For all oxygenated solvents, C(p)E is positive and V(E) negative, while for the equal-structure hydrocarbon solvents (taken as homomorphs), they are of the opposite sign. This is interpreted in terms of the formation of H-bonded complexes between the oxygen atom in the solvent molecule and the highly acidic hydrogen atom in halothane. For benzene, C(p)E and V(E) are positive but small; this is consistent with the weak electron-donor character of benzene and indicates the presence of a weak halothane/BENZ complexation which most probably occurs through a charge transfer mechanism similar to that present in mixtures of fully halogenated freons, such as Freon 113, with oxygenated solvents. The use of the homomorphs indicated that (i) for halothane +DPE, +DIPE, and +MTBE, the asymmetry of the C(p)E curves and their opposite-sign curvatures at low and high halothane concentrations are mainly due to the physical contributions to C(p)E, and (ii) for halothane +ACT, +MAC, and +DIOX, the solutions contain multisolvated species.