Received 9 December 2005
trans-1,4-Dimethylcyclohexane, C8H16, was studied as part of a project to develop a computer-controlled low-temperature crystal-growing device. The liquid crystallizes with the molecule lying on a centre of symmetry, leading to Z' = .
trans-1,4-Dimethylcyclohexane, (I) (Fig. 1), was one of eight alkylcyclohexanes whose thermodynamic properties were published in 1949 (Huffman et al., 1949). That work reported a melting point of 236.217 K and showed no evidence for phase changes in the range down to liquid-nitrogen temperatures.
The sample used for the present study was one of several sealed in 0.2 mm Lindeman tubes for preliminary work carried out in 1979. Data had been collected at that time on a Stoe Weissenberg diffractometer and the structure solved, but it was not of a publishable quality (Courseille et al., 1979).
The sample solidified spontaneously to a polycrystalline mass on flash cooling to 150 K. The temperature was then raised to 230 K and the sample zone-refined into a single-crystal using tandem computer-controlled heating elements. The temperature was then slowly reduced to 150 K for data collection.
The structure of (I) consists of molecules lying on centres of symmetry. This leads to the packing consisting of columns of molecules lying along the b axis (Fig. 2), with the mean plane of the molecule inclined at 145° to that axis (Fig. 3).
| || Figure 1 |
The structure of (I), with displacement ellipsoids drawn at the 50% probability level and H atoms shown as spheres of arbitary radii. Unlabelled atoms are related to labelled atoms by a centre of symmetry.
| || Figure 2 |
A projection of (I) along the b axis. The low specific gravity (0.98 Mg m-3) is explained by the open texture of the structure.
| || Figure 3 |
A projection of (I) along the c axis, showing the molecular stacks parallel to the b axis.
The material was used as supplied by Aldrich Chemical Company Inc. in 1979.
The H atoms were all located in a difference map and then repositioned geometrically. The H atoms were initially refined with soft restraints on the bond lengths and angles to regularize their geometry, with C-H distances in the range 0.93-0.98 Å, and on the displacement parameters, with Uiso(H) = 1.2-1.5 times Ueq of the parent atom, after which their positions were refined with riding constraints.
Data collection: COLLECT (Nonius, 2001).; cell refinement: DENZO/SCALEPACK; data reduction: DENZO/SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: CRYSTALS.
Altomare, A., Cascarano, G., Giacovazzo, C., Guagliardi, A., Burla, M. C., Polidori, G. & Camalli, M. (1994). J. Appl. Cryst. 27, 435.
Betteridge, P. W., Carruthers, J. R., Cooper, R. I., Prout, C. K. & Watkin, D. J. (2003). J. Appl. Cryst. 36, 1487.
Courseille, D., Hospital, M., Leroy, F. & Watkin, D. (1979). 5th European Crystallographic Meeting, Copenhagen, Denmark, p. 285.
Huffman, H. M., Todd, S. S. & Oliver, G. D. (1949). J. Am. Chem. Soc. 71, 584-592.
Nonius (2001). COLLECT. Nonius BV, Delft, The Netherlands.
Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307-326. New York: Academic Press.
Watkin, D. J., Prout, C. K. & Pearce, L. J. (1996). CAMERON. Chemical Crystallography Laboratory, University of Oxford, England.