ORTHO-EFFECTS OF CHLOROBENZOIC AND NITROBENZOIC ACIDS IN WATER-DIMETHYLSULFOXIDE MIXTURES AT 25-DEGREES-C

The dissociation of ortho-chloro- and nitro-benzoic acids in water-DMSO mixtures (0.0 + 0.8 DMSO mole fraction) was studied by means of a linear combination of the ordinary polar, proximity polar, and steric effects. Enthalpic and entropic contributions to substituent effects for the ortho-derivatives were also examined. The dissociation of the ortho-chloro-derivatives appear to be mostly anion-controlled. However, for the ortho-nitro-derivatives, the steric inhibition of solvation on the undissociated molecules may also be involved in controlling the course of the reaction. © 1979.