Titrations in non-aqueous media. Part XV. Redoximetric titrations of anthracene and anthracene derivatives with manganese(III) acetate in glacial acetic acid

Abstract

Anthracene, 9-methylanthracene, 9-phenylanthracene, 9-chloroanthracene, 9-anthracenecarbaldehyde, 9,10-diphenylanthracene, 9,10-dibromoanthracene, 9,10-anthracenedicarbaldehyde, 9,10-ditolylanthracene, 9-cyanoanthracene, 9,10-dicyanoanthracene, 9-cyano-10-methoxyanthracene, 9-chloro-10-cyanoanthracene and dibenz[a,h]anthracene were titrated redoximetrically with manganese(III) acetate in glacial acetic acid. Titrations were carried out at 60 °C, both directly and indirectly. Because the direct titrations are time consuming, the indirect titrations were found to be the more practical. For the indirect titrations a hydroquinone solution was used as a back-titrant. The end-points were determined potentiometrically using a redox platinum and silver-silver chloride electrode assembly. The first nine compounds listed above participated in two-electron redox reactions to produce anthraquinone and its derivatives. The remaining five compounds did not undergo a redox reaction. This is probably due to the very strong electron-withdrawing effect of the cyano group or to the fused benzene rings.