trans-1,2-Dimethyl­cyclo­hexa­ne

Bream, R.; Watkin, D.; Cowley, A.

doi:10.1107/S1600536806002741

organic compounds

CRYSTALLOGRAPHIC
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ISSN: 2056-9890

Volume 62| Part 2| February 2006| Pages o785-o787

https://doi.org/10.1107/S1600536806002741

trans-1,2-Dimethylcyclohexane

Richard Bream,^a ^* David Watkin ^a and Andrew Cowley ^a

^aChemical Crystallography, Central Chemistry Laboratory, University of Oxford, Oxford OX1 3TA, England
^*Correspondence e-mail: richard.bream@pmb.ox.ac.uk

(Received 11 January 2006; accepted 23 January 2006; online 27 January 2006)

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 ).

Figure 1
The title compound with displacement ellipsoids drawn at the 50% probability level. H atoms are shown as spheres of arbitary radius.

Figure 2
An a axis projection of the title compound. One column of molecules has been highlighted in blue for comparison with Fig. 3

Figure 3
A projection along the c axis, showing the molecular stacks parallel to the a axis.

Experimental

The material was used as supplied by the Aldrich Chemical Company Inc. in 1979.

Crystal data

C₈H₁₆
M_r = 112.22
Monoclinic, P 2₁ /n
a = 5.3403 (4) Å
b = 19.4410 (15) Å
c = 7.4446 (7) Å
β = 92.378 (4)°
V = 772.24 (11) Å³
Z = 4
D_x = 0.965 Mg m⁻³
Mo Kα radiation
Cell parameters from 1440 reflections
θ = 5–27°
μ = 0.05 mm⁻¹
T = 150 K
Cylinder, colourless
1.00 × 0.20 (radius) mm

Data collection

Nonius KappaCCD diffractometer
ω scans
Absorption correction: multi-scan(DENZO/SCALEPACK; Otwinowski & Minor, 1997 )T_min = 0.86, T_max = 0.97
2938 measured reflections
1679 independent reflections
1677 reflections with I > −3σ(I)
R_int = 0.039
θ_max = 27.4°
h = −6 → 6
k = −25 → 22
l = −9 → 9

Refinement

Refinement on F²
R[F² > 2σ(F²)] = 0.083
wR(F²) = 0.149
S = 1.01
1677 reflections
73 parameters
H-atom parameters constrained
w = 1/[σ²(F²) + (0.05P)² + 0.29P] where P = [max(F_o²,0) + 2F_c²]/3
(Δ/σ)_max = 0.004
Δρ_max = 0.23 e Å⁻³
Δρ_min = −0.20 e Å⁻³

Table 1
Selected geometric parameters (Å, °)

C1—C2	1.531 (2)
C1—C6	1.531 (2)
C1—C8	1.529 (2)
C2—C3	1.529 (2)
C2—C7	1.531 (2)
C3—C4	1.526 (2)
C4—C5	1.521 (2)
C5—C6	1.526 (2)

C2—C1—C6	110.81 (12)
C2—C1—C8	113.12 (13)
C6—C1—C8	110.15 (12)
C1—C2—C3	110.76 (12)
C1—C2—C7	112.87 (12)
C3—C2—C7	110.38 (12)
C2—C3—C4	112.76 (12)
C3—C4—C5	110.67 (12)
C4—C5—C6	111.00 (13)
C1—C6—C5	112.93 (12)

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 [U_iso(H) = 1.2–1.5U_eq(C)], 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.

Supporting information

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S1600536806002741/fl6215sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536806002741/fl6215Isup2.hkl

Computing details top

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.

trans-1,2-dimethyl-cyclohexane top

Crystal data top

C₈H₁₆	D_x = 0.965 Mg m⁻³
M_r = 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

Data collection top

Nonius KappaCCD diffractometer	1677 reflections with I > −3σ(I)
Graphite monochromator	R_int = 0.039
ω scans	θ_max = 27.4°, θ_min = 5.2°
Absorption correction: multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997)	h = −6→6
T_min = 0.86, T_max = 0.97	k = −25→22
2938 measured reflections	l = −9→9
1679 independent reflections

Refinement top

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(F_o²,0) + 2F_c²]/3
S = 1.01	(Δ/σ)_max = 0.004
1677 reflections	Δρ_max = 0.23 e Å⁻³
73 parameters	Δρ_min = −0.20 e Å⁻³
0 restraints

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
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*

Atomic displacement parameters (Å²) top

	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)

Geometric parameters (Å, º) top

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

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