Hydrogen Bond Linking of Quinol Molecules

Abstract

CRYSTAL structure examination has shown that quinol molecules may link by hydrogen bonds in a special manner. The compound SO2.3C6H4(OH)21 is found to have a rhombohedral lattice; the corresponding hexagonal unit cell, a = 16·3, c = 5·81 A., contains nine molecules of quinol and three of sulphur dioxide. From X-ray intensity relationships and absent spectra, the evidence of face development, and the negative results of pyro-electric and piezoelectric tests, the space group should be R3. For β-quinol, Caspari2 found a unit cell of very similar dimensions, without a centre of symmetry, and of the possible space groups C13–C3 and C43–R3 preferred C13–C3; a determination of atomic positions was not attempted. We have confirmed the polar character, but from absent spectra find the space group to be (C43–R3. From the great similarity, after allowance for the sulphur dioxide, between our X-ray data for β-quinol and the sulphur dioxide compound, the two structures must have much in common. As a safeguard, therefore, against erroneous conclusions due to faulty space group suppositions, the structure of the sulphur dioxide compound was developed, without the initial assumption of centrosymmetry, by three-dimensional Patterson and Fourier methods. In the early stages this procedure brought in a symmetry centre, and for the subsequent work the space group was taken as R3 in accordance with this and the other evidence.