AGGREGATION OF LITHIUM PHENOLATES IN WEAKLY POLAR APROTIC SOLVENTS.

Article abstract of DOI:10.1021/ja00351a010

The aggregation of lithium phenolate, 3,5-dimethylphenolate, 2,6-dimethylphenolate, and 2,6-di-tert-butylphenolate in dioxalane, dimethoxyethane, and pyridine has been investigated by a variety of methods including studies of vapor pressure barometry, **1**3C chemical shifts, **7Li nuclear quadrupole coupling constants, and **1**3C spin-lattice relaxation times. The phenolates with no ortho substituents from tetramers under most conditions. In pyridine at low concentrations and temperature the tetramers coexist with dimers. Lithium 2,6-dimethylphenolate forms dimers under all conditions studied, and lithium 2,6-di-tert-butylphenolate exists as a monomer or an oligomer depending on conditions. Attempts to establish solvation numbers for the aggregates from solvent **1**3C relaxation times have not been successful, and the reason for the failure, very fast solvent exchange, is discussed. The kinetics and thermodynamics of exchange between dimers and tetramers of lithium 3,5-dimentylphenolate in pyridine have been investigated, and the mechanism of interconversion is shown to involve additional solvation of the tetramer prior to dissociation.