Dimerization of Phthalate Ion in Non-Aqueous Solvents

Solutions of tetraethylammonium phthalate in non-aqueous solvents (ethanol, dimethylsulfoxide, dimethylformamide, and acetonitrile) were studied by electronic absorption spectroscopy. It was shown that the phthalate anion dimerizes in acetonitrile and dimethylformamide solutions due to π-stacking, the experimental equilibrium constants being 550±50 and 900±50, respectively. Dimerization of the phthalate anion was not observed in ethanol and dimethylsulfoxide solutions.