ACIDITY OF DIBASIC ACIDS .1. THE 2ND ACIDITY CONSTANT OF 9,10-DIHYDRO-ANTHRACENE AND ITS 9,10-SUBSTITUTED DERIVATIVES - EFFECT OF SUBSTITUENT AND COUNTER ION

The second equilibrium ion pair acidity constants (pK2) of 9,10-dihydroanthracene, 9-phenyl-9,10-dihyroanthracene, 9,10-diphenyl-9,10-dihydroanthracene and 9-cyano-9,10-dihydroanthracene with sodium, potassium and rubidium have been determined in tetrahydrofuran (THF) at 25-degrees-C in the concentration range 10(-5)-10(-2) mol dm-3. Equilibria were monitored by UV-VIS and H-1 NMR spectroscopies and the spectra of the dimetallic and monometallic salts reported. The dimetallic salts of all the dibasic carbon acids studied behave as contact ion pairs in THF. The pK2 of 9,10-dihydroanthracene is insensitive to substituent effect but is strongly dependent on the cation.