Persulphate oxidation of o-benzylbenzamide gave mainly 2,2′-bibenzyl-αα′-diyldibenzamide, and smaller amounts of 3-phenylphthalide, 3-phenylphthalimidine, and related dimers. The initial oxidation occurs at the benzyl and not the amide group. Analogous products were obtained from the oxidation of o-benzylbenzoic acid. In both cases dimerisation at the benzylic position was suppressed by addition of copper(II) ions. Persulphate oxidation of o-benzoylbenzamide afforded phthalimide, fluorenone, and o-benzoylbenzoic acid.