trans-1,4-Di­bromo­cyclo­hexane-1,4-di­carboxyl­ic acid

Molecules of the title compound, C₈H₁₀Br₂O₄, located on symmetry centers, are in a rigid chair conformation, with the COOH and Br substituents axial and equatorial, respectively. The carboxyl­ic acid groups form hydrogen bonds, in a cyclic motif, leading to infinite chains along the b axis.

Key indicators

• Single-crystal X-ray study
• T = 110 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.026
• wR factor = 0.077
• Data-to-parameter ratio = 14.6

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

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S1. Comment

This paper is part of a study of the molecular conformation and crystal polarity of trans-1,4-di- and tetrasubstituted symmetrical cyclohexanes (Echeverría et al., 2000, 1995a,b). The intramolecular bond lengths and the endocyclic bond angles that describe the molecular conformation of the title compound, (I), are given in Table 1. The mean C—C ring bond length and the mean endocyclic angle are 1.532 (3) Å and 110.7 (2)°, respectively; the latter value being close to the value for the ideal cyclohexane ring, C—C—C 111.1° (Bucourt & Hainaut, 1965) and to the observed mean value in the parent compound trans-1,4-cyclohexanedicarboxylic acid, (II) [111.4 (4)°; Dunitz & Strickler, 1966; Von Luger et al., 1972]. The cyclohexane ring, as described by the puckering parameters (Cremer & Pople, 1975), Q_T = 0.585 (2) Å, θ = 0.0 (1)° and ϕ undefined, is not distorted. The torsion angle C1—C2—C3ⁱ—C1ⁱ in (I), 56.2 (2)°, can be compared with 53.4 (3)° in (II), 54.8 (8)° in trans-1,4-dibromocyclohexane-1,4-dicarbonitrile (Echeverría, 1995a), and 57.1 (3)° in trans-cyclohexane-1,4-dicarbonitrile (Echeverría, 1995b). In contrast to observations in other studies, where flatter chairs were found as the size of substituents was increased (Juaristi, 1995; Echeverría et al., 2000), the molecule of (I) exhibits a more pronounced chair conformation. The exocyclic angle involving the substituents (C4—C1—Br1) is 102.2 (1)°. This departs from the experimental H_eq—C—H_ax value, 106.6°, obtained from isotopomers of cyclohexane selectively substituted with deuterium and ¹³C, using pulsed microwave Fourier transform spectroscopy (Dommen et al., 1990). The R_eq—C—R_ax angle in (I) is also smaller than the values obtained in other heavily substituted cyclohexanes, that include halogens and/or carboxymethyl groups, e.g. 105.7 (1)° in trans-dimethyl 1,4-bis(difluoromethyl)cyclohexane-1,4-dicarboxylate (Swenson et al., 1996) and 106.7 (2)° in 1Ha:2He/4Ha:5He-octafluorocyclohexane (Goodhand & Hamor, 1978). In spite of the equatorial position of Br, the C—Br bond length, 1.988 (2) Å, is longer than the C—Br bond length, 1.834 Å, observed in trans-1,4-dibromocyclohexane (Hassel & Hadler Vihovde, 1953). This is consistent with the elongation predicted by HF calculations in overcrowded, perhalogenated cyclohexanes (Ciolowski et al., 1995).

The three-dimensional structure consists of infinite chains extending in the b direction. These chains result from hydrogen bonds, in a cyclic motif, formed by the carboxylic acid groups (Table 2). The chains are linked by weak C—H···O bonds (Steiner et al., 2002) and weak C—H···Br contacts.

S2. Experimental

The title compound was synthesized according to Barón et al. (1975) and crystallized by slow evaporation from acetone.

S3. Refinement

H atoms bound to C atom were located in difference Fourier syntheses and were refined freely in isotropic mode. The H atom of the hydroxyl group was stereochemically positioned and allowed to ride on the bound O atom. The O—H bond was also allowed to rotate about the C—O bond. The largest difference electron-density peak is 0.94 Å from Br1.

Computing details

Data collection: SMART-NT (Bruker, 1998); cell refinement: SMART-NT; data reduction: SAINT-NT (Bruker, 1998); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 1990), PARST (Nardelli, 1983, 1995) and ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

	Fig. 1. A view of (I), with displacement ellipsoids drawn at the 50% probability level.
	Fig. 2. A view, along b, of the unit-cell contents for (I).

(I)

Crystal data

C8H10Br2O4	Dx = 2.204 Mg m^−3
Mr = 329.98	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pbca	Cell parameters from 914 reflections
a = 10.5125 (8) Å	θ = 11.5–26.3°
b = 8.3836 (5) Å	µ = 8.14 mm^−1
c = 11.2817 (9) Å	T = 110 K
V = 994.29 (12) Å^3	Prism, colourless
Z = 4	0.20 × 0.13 × 0.10 mm
F(000) = 640

Data collection

Bruker SMART 1K CCD diffractometer	1224 independent reflections
Radiation source: fine-focus sealed tube	975 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.041
ω scans	θmax = 28.2°, θmin = 3.6°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −13→13
Tmin = 0.244, Tmax = 0.443	k = −11→11
10606 measured reflections	l = −13→15

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.027	Hydrogen site location: difference Fourier map
wR(F^2) = 0.077	H atoms treated by a mixture of independent and constrained refinement
S = 1.06	w = 1/[σ^2(Fo^2) + (0.0491P)^2 + 0.3512P] where P = (Fo^2 + 2Fc^2)/3
1224 reflections	(Δ/σ)max = 0.001
84 parameters	Δρmax = 1.04 e Å^−3
0 restraints	Δρmin = −0.56 e Å^−3

Special details

Experimental. SADABS has been used for a true 2θ dependent absorption correction. The value of mu*t used was 0.8

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Br1	0.748735 (19)	0.14791 (3)	0.35473 (2)	0.01766 (13)
O1	0.47439 (18)	0.3451 (2)	0.38949 (16)	0.0177 (4)
O2	0.57933 (17)	0.35366 (17)	0.56340 (15)	0.0167 (4)
C3	0.6237 (2)	0.0233 (3)	0.5610 (2)	0.0136 (4)
C2	0.4990 (2)	0.0173 (3)	0.3698 (2)	0.0132 (4)
C1	0.5904 (2)	0.1125 (2)	0.4474 (2)	0.0130 (5)
C4	0.5459 (2)	0.2838 (2)	0.47227 (19)	0.0127 (4)
H1	0.4565	0.4376	0.4071	0.053 (11)*
H32	0.676 (3)	0.090 (4)	0.610 (3)	0.024 (7)*
H31	0.670 (3)	−0.078 (3)	0.540 (2)	0.016 (7)*
H21	0.544 (3)	−0.077 (3)	0.345 (2)	0.012 (7)*
H22	0.478 (2)	0.078 (3)	0.300 (2)	0.009 (6)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.01612 (18)	0.01552 (19)	0.0213 (2)	−0.00093 (8)	0.00486 (8)	−0.00113 (8)
O1	0.0255 (10)	0.0067 (8)	0.0210 (9)	0.0025 (7)	−0.0030 (7)	−0.0002 (7)
O2	0.0228 (9)	0.0094 (7)	0.0180 (9)	0.0013 (6)	−0.0020 (7)	−0.0018 (6)
C3	0.0127 (10)	0.0100 (9)	0.0181 (12)	0.0011 (8)	−0.0028 (9)	−0.0001 (8)
C2	0.0162 (11)	0.0098 (10)	0.0137 (12)	0.0004 (9)	−0.0017 (8)	−0.0002 (8)
C1	0.0137 (11)	0.0073 (9)	0.0179 (12)	−0.0001 (7)	0.0011 (9)	−0.0007 (8)
C4	0.0144 (10)	0.0089 (9)	0.0148 (11)	−0.0023 (8)	0.0011 (8)	0.0014 (8)

Geometric parameters (Å, º)

Br1—C1	1.988 (2)	C3—H31	1.01 (3)
O1—C4	1.304 (3)	C2—C1	1.525 (3)
O1—H1	0.82	C2—C3^i	1.545 (3)
O2—C4	1.235 (3)	C2—H21	0.97 (3)
C3—C1	1.525 (3)	C2—H22	0.96 (3)
C3—C2^i	1.545 (3)	C1—C4	1.536 (3)
C3—H32	0.96 (3)
C4—O1—H1	109.47	C3^i—C2—H22	109.9 (15)
C1—C3—C2^i	109.97 (18)	H21—C2—H22	108 (2)
C1—C3—H32	109.5 (18)	C3—C1—C2	111.75 (18)
C2^i—C3—H32	108.3 (18)	C3—C1—C4	111.99 (18)
C1—C3—H31	109.2 (15)	C2—C1—C4	113.69 (18)
C2^i—C3—H31	109.8 (16)	C3—C1—Br1	108.88 (15)
H32—C3—H31	110 (2)	C2—C1—Br1	107.70 (16)
C1—C2—C3^i	110.57 (18)	C4—C1—Br1	102.23 (13)
C1—C2—H21	106.7 (16)	O2—C4—O1	125.0 (2)
C3^i—C2—H21	112.1 (16)	O2—C4—C1	120.60 (19)
C1—C2—H22	109.5 (14)	O1—C4—C1	114.39 (19)
C1—C2—C3^i—C1^i	−56.1 (2)	C3—C1—C4—O2	25.0 (3)
C2^i—C3—C1—C2	−56.8 (2)	C2—C1—C4—O2	152.8 (2)
C2^i—C3—C1—C4	72.1 (2)	Br1—C1—C4—O2	−91.4 (2)
C2^i—C3—C1—Br1	−175.6 (1)	C3—C1—C4—O1	−156.2 (2)
C3^i—C2—C1—C3	57.1 (2)	C2—C1—C4—O1	−28.4 (3)
C3^i—C2—C1—C4	−70.8 (2)	Br1—C1—C4—O1	87.4 (2)
C3^i—C2—C1—Br1	176.7 (1)

Symmetry code: (i) −x+1, −y, −z+1.