organic compounds
trans-1,2-Dimethylcyclohexane
aChemical Crystallography, Central Chemistry Laboratory, University of Oxford, Oxford OX1 3TA, England
*Correspondence e-mail: richard.bream@pmb.ox.ac.uk
The title compound, C8H16, a liquid at room temperature, was studied as part of a project to develop a computer-controlled low-temperature crystal-growing device. Single crystals, in P21/n, were obtained at 167 K. The molecule adopts a chair conformation and possesses a non-crystallographic twofold axis of symmetry.
Comment
trans-1,2-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 184.994 K and showed no evidence for phase changes in the range down to liquid nitrogen temperatures.
The sample we used 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 was not of a publishable quality (Courseille et al., 1979).
The sample solidified spontaneously to a polycrystalline mass on flash cooling to 120 K. The temperature was then raised to 167 K and the sample was 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 molecules are in the chair conformation with the two methyl groups trans-equatorial [τ = −58.0 (2)]. The molecule has an excellent internal twofold axis (r.m.s. positional deviation 0.03 Å, r.m.s. bond length deviation 0.01 Å and r.m.s. torsion angle deviation 1.6° including the refined H atoms). The van der Waals surface is in the form of a slightly elongated disk with alternate layers inclined to each other. The calculated density is not unlike that of the ordered monoclinic phase of cyclohexane (0.996 Mg m−3), suggesting that a low specific gravity may be a feature of small chain cyclic hydrocarbons (Kahn et al., 1973).
Experimental
The material was used as supplied by the Aldrich Chemical Company Inc. in 1979.
Crystal data
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Refinement
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The H atoms were all located in a difference map and then repositioned geometrically. They were initially refined with soft restraints on the bond lengths and angles to regularize their geometry (C—H = 0.93–0.98 Å) and displacement parameters [Uiso(H) = 1.2–1.5Ueq(C)], after which their positions were refined with riding constraints.
Data collection: COLLECT (Nonius, 2001); cell 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.
Supporting information
https://doi.org/10.1107/S1600536806002741/fl6215sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536806002741/fl6215Isup2.hkl
Data collection: COLLECT (Nonius, 2001); cell
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.C8H16 | Dx = 0.965 Mg m−3 |
Mr = 112.22 | Melting point: 184.994 K |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
a = 5.3403 (4) Å | Cell parameters from 1440 reflections |
b = 19.4410 (15) Å | θ = 5–27° |
c = 7.4446 (7) Å | µ = 0.05 mm−1 |
β = 92.378 (4)° | T = 150 K |
V = 772.24 (11) Å3 | Cylinder, colourless |
Z = 4 | 1.00 × 0.20 (radius) mm |
F(000) = 256 |
Nonius KappaCCD diffractometer | 1677 reflections with I > −3σ(I) |
Graphite monochromator | Rint = 0.039 |
ω scans | θmax = 27.4°, θmin = 5.2° |
Absorption correction: multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997) | h = −6→6 |
Tmin = 0.86, Tmax = 0.97 | k = −25→22 |
2938 measured reflections | l = −9→9 |
1679 independent reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.083 | H-atom parameters constrained |
wR(F2) = 0.149 | w = 1/[σ2(F2) + (0.05P)2 + 0.29P] where P = [max(Fo2,0) + 2Fc2]/3 |
S = 1.01 | (Δ/σ)max = 0.004 |
1677 reflections | Δρmax = 0.23 e Å−3 |
73 parameters | Δρmin = −0.20 e Å−3 |
0 restraints |
x | y | z | Uiso*/Ueq | ||
C1 | 0.7205 (3) | 0.10079 (7) | 0.29818 (19) | 0.0409 | |
C2 | 0.4530 (3) | 0.12850 (7) | 0.27380 (19) | 0.0393 | |
C3 | 0.4130 (3) | 0.18962 (8) | 0.39864 (19) | 0.0422 | |
C4 | 0.4752 (3) | 0.17273 (8) | 0.5957 (2) | 0.0445 | |
C5 | 0.7418 (3) | 0.14581 (8) | 0.6199 (2) | 0.0451 | |
C6 | 0.7843 (3) | 0.08472 (8) | 0.4962 (2) | 0.0431 | |
C7 | 0.3833 (4) | 0.14810 (9) | 0.0788 (2) | 0.0508 | |
C8 | 0.7683 (4) | 0.03765 (9) | 0.1821 (2) | 0.0532 | |
H11 | 0.8373 | 0.1384 | 0.2618 | 0.0482* | |
H21 | 0.3394 | 0.0905 | 0.3103 | 0.0464* | |
H31 | 0.5218 | 0.2279 | 0.3634 | 0.0510* | |
H32 | 0.2359 | 0.2055 | 0.3837 | 0.0504* | |
H41 | 0.4519 | 0.2148 | 0.6686 | 0.0539* | |
H42 | 0.3575 | 0.1364 | 0.6321 | 0.0538* | |
H51 | 0.7789 | 0.1322 | 0.7491 | 0.0538* | |
H52 | 0.8556 | 0.1841 | 0.5909 | 0.0538* | |
H61 | 0.9627 | 0.0704 | 0.5102 | 0.0513* | |
H62 | 0.6790 | 0.0465 | 0.5304 | 0.0527* | |
H71 | 0.2144 | 0.1700 | 0.0727 | 0.0746* | |
H72 | 0.5042 | 0.1815 | 0.0397 | 0.0756* | |
H73 | 0.3827 | 0.1069 | 0.0005 | 0.0756* | |
H81 | 0.9407 | 0.0204 | 0.2094 | 0.0792* | |
H82 | 0.7535 | 0.0497 | 0.0548 | 0.0792* | |
H83 | 0.6466 | 0.0027 | 0.2082 | 0.0802* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0482 (9) | 0.0385 (8) | 0.0364 (8) | −0.0018 (6) | 0.0068 (7) | −0.0021 (6) |
C2 | 0.0477 (9) | 0.0398 (8) | 0.0307 (7) | −0.0016 (6) | 0.0032 (6) | −0.0001 (6) |
C3 | 0.0481 (9) | 0.0435 (8) | 0.0353 (8) | 0.0038 (7) | 0.0043 (6) | −0.0003 (6) |
C4 | 0.0514 (10) | 0.0502 (9) | 0.0323 (8) | 0.0010 (7) | 0.0046 (7) | −0.0044 (7) |
C5 | 0.0514 (10) | 0.0507 (9) | 0.0331 (8) | −0.0014 (7) | 0.0013 (6) | −0.0031 (7) |
C6 | 0.0463 (9) | 0.0419 (8) | 0.0408 (9) | 0.0008 (7) | −0.0001 (7) | 0.0004 (6) |
C7 | 0.0678 (11) | 0.0524 (9) | 0.0320 (8) | 0.0048 (8) | 0.0011 (7) | 0.0008 (7) |
C8 | 0.0616 (11) | 0.0515 (10) | 0.0466 (9) | 0.0075 (8) | 0.0029 (8) | −0.0104 (8) |
C1—C2 | 1.531 (2) | C4—H42 | 0.990 |
C1—C6 | 1.531 (2) | C5—C6 | 1.526 (2) |
C1—C8 | 1.529 (2) | C5—H51 | 1.009 |
C1—H11 | 1.005 | C5—H52 | 0.990 |
C2—C3 | 1.529 (2) | C6—H61 | 0.994 |
C2—C7 | 1.531 (2) | C6—H62 | 0.972 |
C2—H21 | 1.001 | C7—H71 | 0.997 |
C3—C4 | 1.526 (2) | C7—H72 | 0.969 |
C3—H31 | 0.986 | C7—H73 | 0.991 |
C3—H32 | 0.997 | C8—H81 | 0.993 |
C4—C5 | 1.521 (2) | C8—H82 | 0.977 |
C4—H41 | 0.992 | C8—H83 | 0.966 |
C2—C1—C6 | 110.81 (12) | C4—C5—C6 | 111.00 (13) |
C2—C1—C8 | 113.12 (13) | C4—C5—H51 | 110.4 |
C6—C1—C8 | 110.15 (12) | C6—C5—H51 | 110.1 |
C2—C1—H11 | 107.4 | C4—C5—H52 | 107.2 |
C6—C1—H11 | 107.0 | C6—C5—H52 | 110.2 |
C8—C1—H11 | 108.1 | H51—C5—H52 | 107.8 |
C1—C2—C3 | 110.76 (12) | C1—C6—C5 | 112.93 (12) |
C1—C2—C7 | 112.87 (12) | C1—C6—H61 | 109.4 |
C3—C2—C7 | 110.38 (12) | C5—C6—H61 | 108.7 |
C1—C2—H21 | 106.3 | C1—C6—H62 | 107.5 |
C3—C2—H21 | 107.9 | C5—C6—H62 | 109.6 |
C7—C2—H21 | 108.4 | H61—C6—H62 | 108.7 |
C2—C3—C4 | 112.76 (12) | C2—C7—H71 | 109.5 |
C2—C3—H31 | 109.0 | C2—C7—H72 | 108.2 |
C4—C3—H31 | 108.1 | H71—C7—H72 | 108.2 |
C2—C3—H32 | 109.2 | C2—C7—H73 | 110.6 |
C4—C3—H32 | 109.9 | H71—C7—H73 | 109.7 |
H31—C3—H32 | 107.6 | H72—C7—H73 | 110.5 |
C3—C4—C5 | 110.67 (12) | C1—C8—H81 | 109.3 |
C3—C4—H41 | 108.7 | C1—C8—H82 | 110.3 |
C5—C4—H41 | 110.9 | H81—C8—H82 | 108.5 |
C3—C4—H42 | 107.5 | C1—C8—H83 | 108.8 |
C5—C4—H42 | 108.9 | H81—C8—H83 | 110.3 |
H41—C4—H42 | 110.1 | H82—C8—H83 | 109.7 |
References
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