Solid state complexes of polymethylated quinones with polymethylated phenols. The crystal structure of the 2:1 complex of 2,5-dimethyl-1,4-benzoquinone with 2,5-dimethyl-1,4-dihydroxybenzene

Abstract

2,5-Dimethyl-1,4-benzoquinone and 2,5-dimethylhydroquinone have been found to form a 2:1 complex instead of the more usual 1:1 quinhydrone. The crystal structure and Fourier transform i.r. spectrum of this complex have been determined. The structure is monoclinic, space group P21/c, with a= 10.480(4), b= 12.344(3), c= 9.301(3)Å, β= 115.91(2)°,Z= 2,(C8H8O2)2·C8H10O2. The structure has been determined by direct methods and refined to R 0.051 for the 1 404 reflections recorded with an automatic single crystal diffractometer. Duroquinhydrone has been re-examined and the 1H n.m.r. spectrum in solution as well as the Fourier transform i.r. spectrum of the solid (paraffin oil mull) have confirmed the previous assumption that, in spite of the steric crowding introduced by the eight methyl groups, this is a 1:1 complex, although the position of the oxygen–hydrogen stretching frequency, higher than is found with other quinhydrones, suggests that the hydrogen bonded structure in this complex is significantly affected by the presence of the methyl groups.