1,14-Di­bromo­tetra­decane

In the title compound, C₁₄H₂₈Br₂, the mol­ecule is centrosymmetric and the molecular skeleton, including both terminal Br atoms, has an all-trans conformation. In the crystal structure, the mol­ecules form layers in which the long axes of the mol­ecules are inclined with respect to the layers. The molecules are arranged in a zigzag manner in the neighboring layers, making a herring-bone motif just as in the tilt-smectic C phase of liquid crystals.

Key indicators

• Single-crystal X-ray study
• T = 296 K
• Mean [sigma](C-C) = 0.006 Å
• R factor = 0.043
• wR factor = 0.099
• Data-to-parameter ratio = 21.1

checkCIF results

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S1. Comment

Normal long-chain aliphatic compounds such as n-alkanes, a-monosubstituted n-alkanes, and α,ω-disubstituted n-alkanes, have been investigated for disclosing the principles of organic chemical crystallography and basic polymer science because the molecular skeleton consists of a simple trans zigzag straight hydrocarbon chain. The molecular shape of these compounds can be regarded as rod-like, which is one of the typical features of liquid crystalline molecules, and the molecules in the crystalline state form a layered structure similar to those of the smectic liquid crystalline phase. Moreover, some of them exhibit a high-temperature rotator phase just below their melting points in which molecules have motional freedom in some degree as well as that in liquid crystals. Therefore, normal long-chain aliphatic compounds have also been investigated as models for the smectic liquid crystals.

In these investigations, it is important to obtain the detailed crystal data. Up until now, many researchers have studied crystal structures of many different kinds of normal long-chain aliphatic compounds, for example, n-alkanes (e.g. Nyburg & Gerson, 1992), n-primary alcohols (e.g. Michaud et al., 2000), and α,ω-disubstituted n-alkanes such as 1,12-dibromododecane (Kulpe et al., 1981) and 11-bromoundecane-1-ol (Rosen & Hybl, 1972). Recently, we have systematically analyzed the crystal structures of alkane-α,ω-diols containing 10–19 and 21–23 C atoms (Nakamura et al., 2001; Uno et al., 2002), and we have studied the phase-transition phenomena of the series of alkane-α,ω-diols containing 13–24 C atoms (Ogawa & Nakamura, 1999). In addition, we have also analyzed the crystal structures of 1,16-dibromohexadecane (Kobayashi et al., 1995) and 1,18-dibromooctadecane (Nakamura et al., 1993) in order to elucidate the effect of the terminal groups in normal long-chain aliphatic compounds. Against these backgrounds, we have carried out the crystal structure analysis of 1,14-dibromotetradecane, (I). In this paper, the crystal structure of (I) is described and compared with those of the homologous series and the analogous compounds.

The molecular structure of (I) is shown in Fig. 1. The molecule is centrosymmetric and all torsion angles are about ±180°, that is, the molecular skeleton containing both terminal Br atoms has an all-trans conformation. Fig. 2 shows the projection of the crystal structure of (I) along the b axis. The molecules form layers with a thickness of c/2. In the layer, the long axes of the molecules are inclined at 37.9 (1)° with respect to the normal line to the basal plane of Br atoms, the ab plane. This layer structure is similar to those of the triclinic structure of the even-numbered n-alkanes containing 6–24 C atoms, but the inclination angle of (I) is larger than those of the even-numbered n-alkanes [e.g. n-icosane: 18.5 (1)°; Nyburg & Gerson, 1992]. It is considered that the arrangement in the layer is influenced by the steric and electrostatic repulsion of Br atoms at both ends. As the result, a molecular position in the layer is slid along the direction of the long axis of the neighboring molecule.

The repulsion also influences the interlayer arrangement so that the molecules between the neighboring layers swivel on its long axis with the dihedral angle of the trans zigzag planes of 30.1 (2)°. Moreover, the layers are arranged in a zigzag manner between the neighboring layers making a herringbone motif just like the tilt–smectic C phase of liquid crystals, as shown in Fig.3. The layers are stacked closely in such a way that the α-CH₂ groups are allowed to fit into the grooves formed by Br atoms with the nearest contacts of 3.758 (3) Å, which agree closely with the van der Waals contacts of 3.75 Å (Rowland & Taylor, 1996). Such a closed packing is observed in the even-numbered alkane-α,ω-diols containing 4–18 and 22 C atoms (e.g. Thalladi et al., 2000), also.

The features in the molecular and crystal structure of (I) are similar to those of the homologous series with an even number of C atoms, viz. 1,12-dibromododecane (Kulpe et al., 1981), 1,16-dibromohexadecane (Kobayashi et al., 1995), and 1,18-dibromooctadecane (Nakamura et al., 1993).

S2. Experimental

The title compound, (I), was synthesized from commercially available 1,14-tetradecanedioic acid (Tokyo Kasei Kogyo Co. Ltd) by esterification, reduction, and bromination. The pure compound was obtained through fractional distillation and recrystallization. The single-crystal of (I) used for the X-ray analysis was grown by slow evaporation from a solution containing a mixture of n-heptane and 2-propanol (1:3).

S3. Refinement

All H atoms were located at idealized positions (C—H = 0.95 Å). The H-atom isotropic displacement parameters were set to be 1.2 U_eq of the parent C atom.

Computing details

Data collection: MSC/AFC Diffractometer Control Software Molecular Structure Corporation, 1992); cell refinement: MSC/AFC Diffractometer Control Software; data reduction: CrystalStructure (Molecular Structure Corporation & Rigaku, 2001); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: CRYSTALS (Watkin et al., 1996); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: CrystalStructure.

Figures

	Fig. 1. The molecular structure of (I), showing the crystallographic numbering scheme [symmetry code: (i) 2 − x, −y, −z]. Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. The projection of the crystal structure of (I) along the b axis.
	Fig. 3. The projection of the crystal structure of (I) along the a axis.

(I)

Crystal data

C14H28Br2	F(000) = 364.00
Mr = 356.16	Dx = 1.440 Mg m^−3
Monoclinic, P21/n	Melting point: 322.9(4) K
Hall symbol: -P 2yn	Cu Kα radiation, λ = 1.54178 Å
a = 5.486 (6) Å	Cell parameters from 22 reflections
b = 5.389 (7) Å	θ = 9.6–19.9°
c = 27.827 (4) Å	µ = 6.06 mm^−1
β = 93.38 (4)°	T = 296 K
V = 821.2 (14) Å^3	Plate, colorless
Z = 2	0.43 × 0.43 × 0.08 mm

Data collection

Rigaku AFC-5R diffractometer	Rint = 0.038
ω scans	θmax = 70.1°
Absorption correction: numerical (NUMABS; Higashi, 1999)	h = −6→1
Tmin = 0.208, Tmax = 0.782	k = 0→6
2304 measured reflections	l = −33→33
1563 independent reflections	1 standard reflections every 150 reflections
1305 reflections with F^2 > 2σ(F^2)	intensity decay: 2.8%

Refinement

Refinement on F^2	w = 1/[0.0002Fo^2 + 8.4σ^2(Fo) + 0.21]/(4Fo^2)
R[F^2 > 2σ(F^2)] = 0.043	(Δ/σ)max < 0.001
wR(F^2) = 0.099	Δρmax = 0.54 e Å^−3
S = 1.00	Δρmin = −0.55 e Å^−3
1563 reflections	Extinction correction: Larson (1970)
74 parameters	Extinction coefficient: 24.8 (2)
H-atom parameters not refined

Special details

Refinement. Refinement using reflections with F² > −3.0 σ(F²). The weighted R-factor (wR) and goodness of fit (S) are based on F². R-factor (gt) are based on F. The threshold expression of F² > 2.0 σ(F²) is used only for calculating R-factor (gt).

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

	x	y	z	Uiso*/Ueq
Br1	−0.1134 (1)	0.8399 (1)	0.21295 (2)	0.0779 (2)
C1	0.0619 (9)	0.5449 (9)	0.1940 (2)	0.072 (1)
C2	0.2116 (8)	0.5888 (9)	0.1518 (2)	0.066 (1)
C3	0.3428 (9)	0.3564 (8)	0.1376 (1)	0.066 (1)
C4	0.4975 (8)	0.3954 (8)	0.0945 (1)	0.065 (1)
C5	0.6325 (8)	0.1670 (8)	0.0796 (1)	0.063 (1)
C6	0.7857 (8)	0.2070 (8)	0.0365 (1)	0.065 (1)
C7	0.9241 (8)	−0.0196 (9)	0.0214 (1)	0.064 (1)
H1	0.1669	0.4926	0.2204	0.0868*
H2	−0.0534	0.4178	0.1860	0.0868*
H3	0.1075	0.6427	0.1254	0.0788*
H4	0.3289	0.7140	0.1599	0.0788*
H5	0.4462	0.3029	0.1642	0.0786*
H6	0.2248	0.2316	0.1297	0.0786*
H7	0.3933	0.4483	0.0681	0.0777*
H8	0.6141	0.5214	0.1025	0.0777*
H9	0.7374	0.1145	0.1060	0.0759*
H10	0.5162	0.0407	0.0717	0.0759*
H11	0.6802	0.2580	0.0100	0.0783*
H12	0.9006	0.3348	0.0443	0.0783*
H13	1.0299	−0.0704	0.0479	0.0771*
H14	0.8093	−0.1476	0.0137	0.0771*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0904 (5)	0.0653 (3)	0.0810 (4)	0.0090 (3)	0.0306 (3)	−0.0013 (3)
C1	0.086 (3)	0.062 (3)	0.072 (3)	0.012 (2)	0.026 (3)	0.005 (2)
C2	0.071 (3)	0.060 (2)	0.067 (2)	0.002 (2)	0.017 (2)	0.003 (2)
C3	0.073 (3)	0.064 (3)	0.061 (2)	0.006 (2)	0.019 (2)	0.002 (2)
C4	0.072 (3)	0.063 (3)	0.062 (2)	0.004 (2)	0.018 (2)	0.003 (2)
C5	0.071 (3)	0.064 (3)	0.056 (2)	0.006 (2)	0.016 (2)	0.001 (2)
C6	0.073 (3)	0.065 (3)	0.058 (2)	0.005 (2)	0.018 (2)	0.002 (2)
C7	0.070 (3)	0.065 (3)	0.059 (2)	0.007 (2)	0.016 (2)	0.002 (2)

Geometric parameters (Å, º)

Br1—C1	1.947 (5)	C2—H4	0.95
C1—C2	1.490 (5)	C3—H5	0.95
C2—C3	1.509 (6)	C3—H6	0.95
C3—C4	1.523 (5)	C4—H7	0.95
C4—C5	1.507 (6)	C4—H8	0.95
C5—C6	1.520 (5)	C5—H9	0.95
C6—C7	1.510 (6)	C5—H10	0.95
C7—C7^i	1.508 (7)	C6—H11	0.95
C1—H1	0.95	C6—H12	0.95
C1—H2	0.95	C7—H13	0.95
C2—H3	0.95	C7—H14	0.95
Br1···Br1^ii	3.758 (3)	Br1···Br1^iii	3.758 (3)
Br1—C1—C2	112.8 (3)	H5—C3—H6	109.5
C1—C2—C3	111.6 (4)	C3—C4—H7	108.3
C2—C3—C4	112.9 (4)	C5—C4—H7	108.3
C3—C4—C5	114.2 (4)	C3—C4—H8	108.3
C4—C5—C6	114.0 (4)	C5—C4—H8	108.3
C5—C6—C7	114.5 (4)	H7—C4—H8	109.5
C6—C7—C7^i	114.6 (5)	C4—C5—H9	108.3
Br1—C1—H1	108.6	C6—C5—H9	108.3
C2—C1—H1	108.6	C4—C5—H10	108.3
Br1—C1—H2	108.6	C6—C5—H10	108.3
C2—C1—H2	108.6	H9—C5—H10	109.5
H1—C1—H2	109.5	C5—C6—H11	108.2
C1—C2—H3	108.9	C7—C6—H11	108.2
C3—C2—H3	108.9	C5—C6—H12	108.2
C1—C2—H4	108.9	C7—C6—H12	108.2
C3—C2—H4	108.9	H11—C6—H12	109.5
H3—C2—H4	109.5	C6—C7—H13	108.2
C2—C3—H5	108.6	C7^i—C7—H13	108.2
C4—C3—H5	108.6	C6—C7—H14	108.2
C2—C3—H6	108.6	C7^i—C7—H14	108.2
C4—C3—H6	108.6	H13—C7—H14	109.5
Br1—C1—C2—C3	−179.3 (3)	C4—C5—C6—C7	179.4 (4)
C1—C2—C3—C4	−180.0 (4)	C5—C6—C7—C7^i	179.8 (5)
C2—C3—C4—C5	179.6 (4)	C6—C7—C7^i—C6^i	180.0
C3—C4—C5—C6	179.8 (4)

Symmetry codes: (i) −x+2, −y, −z; (ii) −x−1/2, y−1/2, −z+1/2; (iii) −x−1/2, y+1/2, −z+1/2.