ACIDITY OF DIBASIC CARBON ACIDS .2. GEOMETRY AND ELECTRONIC-STRUCTUREOF MONO-ANIONS AND DI-ANIONS OF 9,10-DIHYDROANTHRACENE AND ITS DERIVATIVES IN TETRAHYDROFURAN

The geometric structure, charge distribution and heats of formation of 9-R(1)-10-R(2)-9,1 0-dihydroanthracenes (R(1) = R(2) = H; R(1) = Me, R(2) = H; R(1) = R(2) = Me; R(1) = Ph, R(2) = H; R(1) = R(2) = Ph; R(1 ) = CN, R(2) = H), their mono- and di-anions; deprotonated at position s 9 and 10 have been calculated by the AM-1 method. The C-13 chemical shifts of the mono- and di-alkali metal salts have been determined in [H-2(8)]THF. The structures of the mono- and di-anions are nearly plan ar, the dianions being more planar than the monoanions. The hybridizat ion of the deprotonated carbon atoms is nearly sp(2). Phenyl substitue nts subtend angles of 56.5 degrees and 45.0 degrees to the anthracene plane in the mono- and di-anions, respectively. With the exception of the cyano group, there is little participation by the substituents in the delocalization of negative charge. There is a correlation between the pi-electron densities and the change in C-13 chemical shift upon a nion formation from the neutral species. The values of the proportiona lity constants are equal to 120.3 and 133.1 ppm/electron for mono- and di-anions, respectively. The pattern of negative charge distribution in the monoanions of 9,10-dihydroanthracenes is similar to that of sub stituted diphenylmethanes. The first and second acidity constants of s ubstituted 9,10-dihydroanthracenes in the liquid phase follow the patt erns indicated by the gas phase calculations of their relative thermod ynamic stabilities.