ACIDITY OF DIBASIC CARBON ACIDS .3. ION SOLVATION STATE OF MONOMETALLIC SALTS OF 9,10-DIHYDROANTHRACENE AND ITS DERIVATIVES IN THF

The ion solvation state of monometallic salts of 9,10-dihydroanthracen e (DHA) and its 9,10-disubstituted derivatives in THF has studied by W -VIS and H-1 and C-13 NMR spectroscopy, At room temperature, lithium 9 -phenyl-9,10-dihydroanthracen-9-ide, lithium 9,10-dimethyl-9,10-dihydr oanthracenide and lithium 9,10-diphenyl-9,10-dihydroanthracenide exist as solvent separated ion pairs (SSIP). Lithium 9, 10-dihydroanthracen e, lithium 9-methyl-9,10-dihydroanthracen-10-ide and sodium, potassium and rubidium 9-phenyl-9,10-dihydroanthracen-9-ides, 9,10-dimethyl-9,1 0-dihydroanthracenides and 9,10-diphenyl-9,10-dihydroanthracenides exi st as a mixture of SSIP and contact ion pairs (CIP). Sodium, potassium , rubidium and caesium 9,10-dihydroanthracenides, 9-methyl-9,10-dihydr oanthracen-10-ides and 9-cyano-9,10-dihydroanthracenides exist as CIP in solution. The stabilizing effect of the methyl and phenyl substitue nts is more significant for SSIP than for CIP. The thermodynamics for SSIP to CIP conversion is determined for the sodium salts: of DHA and its; derivatives. Delta S-degrees is 27 +/- 2 cal mol(-1) K-1 Delta H degrees increases with substituent size and charge dispersion. A model for the transition of CIP of alkali-metal salts of DHA and its deriva tives into SSIP is suggested. The model takes into account the geometr y and charge distribution in anions.