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.