The crystal and molecular structure of dibenzyl disulphide. The refinement of a structure with high correlation coefficients

Abstract

The crystal structure of dibenzyl disulphide, C6Hs-CH2-S-S-CH2-C6Hs, has been determined from three-dimensional X-ray diffraction data. The crystals are monoclinic and belong to the space group Cc.The unit cell has dimensions a= 13.46, b= 8.23, c= 11.29/~, ~= y= 90 °, fl= 99°30 ', and contains four molecules. Difficulty was exl~erienced because of a very strong tendency to twinning of the crystals, often only detected on high-layer line photographs. Positional and temperature factor parameters for sulphur and carbon atoms have been refined by Fourier, block-diagonal least squares and finally by full-matrix least squares. Refinement was unusually difficult because of large correlation coefficients between parameters, associated with a pseudo twofold axis of symmetry in the molecule. In the final stages, hydrogen atoms were included in fixed positions. The final R value based on 867 independent observed reflexions was 7.9%. The precise chemical nature of the S-S bond is examined. ExperimentalA sample of dibenzyl disulphide was recrystaUized from ethanol and gave colourless plate-like crystals, which showed straight extinction parallel to the plate edges when viewed under the polarizing microscope. The density of the crystals was measured by the method of flotation in aqueous solutions of potassium iodide and found to be 1.28 g.cm -3.Considerable difficulty was experienced in selecting a suitable crystal for X-ray analysis since many crystals which appeared suitable after optical and preliminary X-ray examination proved to be twinned when high layer line Weissenberg photographs were taken. A single crystal of dimensions 0.025 x 0.025 x 0.015 cm was eventually used for X-ray analysis, and threedimensional equi-inclination Weissenberg data were collected for the hkO, hkl...hk8, hOl and hll zones.The intensities of 867 independent reflexions were collected photographically, measured visually and converted to [F] 2 and [FI by applying Lorentz and polarization corrections. In view of the small crystal size and the low absorption coefficient, corrections for absorption were considered unnecessary. No correction was made for extinction. Reflexions too weak to be observed were ignored. Crystal data (C6H5. CH2)2S2, M = 246.3 . Monoclinic, a= 13.46, b = 8.23, c = 11.29A_, all + 0.02~ = ), = 90 °, fl = 99 ° 30' + 30'. U= 1233.5~ 3, Z=4, Din= l'28g.cm -3, De= l'32g.cm -3 F000 = 520, Cu K~, 2 = 1.542 A, ~ = 36 cm -1 .Absent reflexions: hkl when h+k is odd, hOl when l is odd (and when h is odd), 0k0 when k is odd.These absences restrict the space group to Cc or C2/c, but the former was confirmed by the pyroelectric test, the statistical test and by the structure refinement. Structure analysisThere are four molecules in the unit cell, and for the space group Cc these must occupy the general positions (x,y,z); (x,-y,½+z); (½+x,½+y,z) and (½+x, ½-Y, ½+z). Patterson summations were performed with hkO and hOl data, but these were not interpreted in terms of a satisfactory trial structure because of the diffuse nature of the peaks. Th...

Preparation of New Nitrogen-Bridged Heterocycles. 60. Syntheses and Conformational Analyses of Bis(indolizin-1-yl) Disulfides

“…6) According to the literature there are several MO calculations in which a preference of the gauche (cis) form over the anti (trans) form in relation to the disulfide linkage and an energy minimum in the dihedral angle near 90°have been shown. 7,8) Furthermore, some structural data for comparatively simple disulfides such as dimethyl disulfide, 9,10) dibenzyl disulfide, 11) and diphenyl disulfide 12,13) by other investigators were in agreement with this prediction. However, there have not been many studies on the conformations of disulfide compounds and a more detailed investigation of their conformations is still valuable.…”

Bis [o-(bromomethyl)benzyl] disulfide

“…1.408 (7) 1.394 (9) 1.374 (9) 1.386 (8) 1.406 (8) 1.394 (7) 1.413 (7) 1.394 (6) 1.394 (7) 1.398 (9) 1.372 (10) 1.403 (9) C ( (Table 2) closely match corresponding ones in dibenzyl disulfide (Lee & Bryant, 1969;van Dijk & Visser, 1971). The average S-S, S-Csph Br-Csph Car--Csp (ar = aromatic) and Cra,--Car bonds of 2.025 (2), 1.835 (5), 1.978 (6), 1.505 (6) and 1.395 (6) A respectively are all normal.…”

The crystal structure of the monoclinic phase of 2,2-di-tert-butyl-3,3-diphenylthiirane at –140°C

“…However, C-S distances as long as 1.84-1.85 /k have been found, e.g. in dibenzyl disulphide (Lee & Bryant, 1969) …”