NEW STERICALLY HINDERED DI-O-QUINONES OF THE BIPHENYL SERIES

New di-o-quinones of the biphenyl series, namely, l-5,5'-di-tert-butyl biphenyl-3,4,3',4'-diquinones, were synthesized. Their structures were established by IR and NMR spectroscopy. The molecular structure of hy l-5,5'-di-tert-butylbiphenyl-3,4,3',4'-diquinone was established by X- ray structural analysis. The structure is characterized by orthogonal (the torsion angle is 82.9 degrees) mutual arrangement of o-benzoquino ne fragments. ESR studies demonstrated that chemical reduction of diqu inone proceeds in four one-electron stages to form paramagnetic mono- and trianions as intermediates. Quinopyrocatechols, which are intermed iates in the synthesis of di-o-quinones, were isolated and characteriz ed.