Influence of Structural Features on Formation of Solid Charge-Transfer Complexes of Quinones with Carcinogenic and Related Noncarcinogenic Electron Donors¹

Ninety-seven compounds expected to function as electron donors in charge-transfer complex formation were tested by microscopic fusion methods for formation of solid quinone complexes. Donor classes included polycyclic hydrocarbons, nitrogen heterocyclics, aromatic amines, aromatic azo compounds, and some miscellaneous compounds. Carcinogenic and noncarcinogenic substances were present in each group. Methylated benzoquinones, naphthoquinones, and anthraquinones were studied. Vitamin K₁, α-tocopherol quinone, and two Q coenzymes were included in this group.

It was found that for quinones of comparable degree and position of methylation, the order of reactivity is benzoquinones > naphthoquinones ≫ anthraquinones. The benzoquinones react with all categories of donors while the naphthoquinones react primarily with the polycyclic hydrocarbons and aromatic amines. Vitamin K₁ and α-tocopherol quinone form colored melts but no solid complexes and the Q coenzymes form few colored melts and no solid complexes.

2,3-Dimethyl-, trimethyl-, and tetramethyl-1,4-benzoquinone are the most reactive of the group of quinones studied. These quinones are simple homologs of the tocopherol quinones, and they form solid complexes with most of the carcinogenic donors.