δ-Hexabromo­cyclo­dodeca­ne

(1R,2S,5R,6S,9S,10R)-Hexabromo­cyclo­dodecane (C₁₂H₁₈Br₆, δ-HBCD) was crystallized from acetonitrile. The C—Br distances range from 1.962 (8) to 1.982 (8) Å and inter­molecular Br...Br contacts contribute to the formation of layers.

Key indicators

• Single-crystal X-ray study
• T = 294 K
• Mean [sigma](C-C) = 0.013 Å
• R factor = 0.045
• wR factor = 0.107
• Data-to-parameter ratio = 24.5

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT341_ALERT_3_C Low Bond Precision on C-C Bonds (x 1000) Ang ...         13
PLAT410_ALERT_2_C Short Intra H...H Contact  H7A    ..  H10     ..       1.99 Ang.

Alert level G
PLAT793_ALERT_1_G Check the Absolute Configuration of C1     = ...          R
PLAT793_ALERT_1_G Check the Absolute Configuration of C2     = ...          S
PLAT793_ALERT_1_G Check the Absolute Configuration of C5     = ...          R
PLAT793_ALERT_1_G Check the Absolute Configuration of C6     = ...          S
PLAT793_ALERT_1_G Check the Absolute Configuration of C9     = ...          S
PLAT793_ALERT_1_G Check the Absolute Configuration of C10    = ...          R

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   2 ALERT level C = Check and explain
   6 ALERT level G = General alerts; check

   6 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   1 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

1,2,5,6,9,10-Hexabromocyclododecane (HBCD) is a widely used brominated flame retardant with a complex stereochemistry (Heeb et al., 2005; Law et al., 2005). The commercial HBCD mixture consists largely of a mixture of three diastereomeric pairs of enantiomers, termed (±) α, β, and γ-HBCD with the γ-isomers as main component (Groweiss et al., 1991; Becher, 2005). Recently the presence of small amounts of δ- and ε-HBCD diastereomers in both technical mixture and environmental samples has been reported (Heeb et al., 2005; Dodder et al., 2006). HBCD has been subject of intensitive studies (i.e. Heeb et al., 2007) as a result of its persistence in the environment, its potential bioactivity and increasing levels in the biosphere (Vos et al., 2003; Covaci et al., 2006; BSEF, 2007). After elucidation of the crystal structure of the six main stereoisomers of the technical mixture (Koeppen et al., 2007,), we directed our attention to the two minor diastereomers. Recently both minor diastereomers were characterized by NMR and their order of elution on a C18 stationary phase was determined (Arsenault et al., 2007). Furthermore, no attempt was made to confirm absolute configurations of δ- and ε-HBCD using single-crystal X-ray crystallography. The knowledge of the three-dimensional structures of all HBCD diastereomers occurring in the environment is necessary for the understanding of the bioaccumulation and the potentially bioisomerization of HBCD. The average C—Br distance in the title compound (Fig. 1) [1.972 (8) Å] is in good agreement with those in the other stereoisomeres (d_av(C—Br)=1.962 (10) -1.974 (13) Å, Koeppen et al., 2007). The average C—C distance of 1.520 (12) Å is also in good agreement with the distances observed in the other HBCD compounds.

The packing of the molecules is mainly influenced by Br···Br interactions. The observed Br···Br contacts range from 3.611 (3) to 3.664 (3) Å and can be classified both as type I (Br5···Br10, d=3.611 (3) Å, θ₁=136.69°, θ₂=154.01°) and II (Br2···Br9, d=3.664 (3) Å, θ₁=83.75°, θ₂=162.48°) contacts, whereas the latter is polarization-induced and contributes actively to crystal structure stabilization (Pedireddi et al., 1994). These contacts lead to the formation of layers parallel to the b-c plane, stacked along the a direction (Fig. 2). The shortest centroid to centroid distances between two HBCD molecules of different layers amount to 5.864 (8) and 5.985 (9) Å, respectively.

Related literature

The corresponding α,-β,- and γ-stereoisomers of HBCD form comparable Br···Br contacts (Koeppen et al., 2007).

For related literature, see: Arsenault et al. (2007); BSEF (2007); Becher (2005); Covaci et al. (2006); Dodder et al. (2006); Groweiss et al. (1991); Heeb et al. (2005, 2007); Law et al. (2005); Pedireddi et al. (1994); Vos et al. (2003).

S2. Experimental

1R,2S,5R,6S,9S,10R-Hexabromocyclododecane (δ-HBCD) was obtained by bromination of trans,trans,trans-cyclododeca-1,5,9-triene (t,t,t-CDT), as illustrated in the reaction scheme (Fig. 3). δ-HBCD was isolated from the reaction mixture by preparative HPLC (C-18 column). For single-crystal x-ray crystallography colourless crystals of δ-HBCD were grown by solvent evaporation from acetonitrile at ambient temperature. LC—MS/MS-experiments ([M—H]^-(m/z 640.6) → [Br]^-(m/z 79.0)) using a combination of a Zorbax XBD-C18 (Agilent Technologies, Waldbronn, Germany) and a chiral NUCLEODEX β-PM (Macherey- Nagel GmbH & Co, Düren, Germany) analytical column shows that δ-HBCD elute between (-)α- and (+)α-HBCD. This corresponds to the results reported in literature (i. e. Arsenault et al., 2007). Spectroscopic Analysis, IR (microscope, cm^-1): 2960, 2937, 2924, 2890, 2862, 2848, 1736, 1459, 1441, 1421, 1373, 1335, 1297, 1278, 1260, 1239, 1157, 1105, 1056, 1037, 1021, 1003, 985, 907, 863, 787, 751, 742, 735, 672, 645, 602.

S3. Refinement

All non-hydrogen atoms were refined anisotropically. The hydrogen atoms were located in difference maps but positioned with idealized geometry and refined using the riding model, with C—H = 0.93–0.97 Å, and U_iso(H) = 1.2U_eq(parent atom).

Computing details

Data collection: SMART (Bruker, 2001); cell refinement: SMART; data reduction: SAINT (Bruker, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPIII (Burnett & Johnson, 1996); software used to prepare material for publication: SHELXTL (Bruker, 2001).

Figures

	Fig. 1. The structure of HBCD with labelling and displacement ellipsoids drawn at the 50% probability level.
	Fig. 2. The crystal packing, showing the layers of HBCD molecules parallel to the b-c plane, connected by Br···Br contacts (green lines).
	Fig. 3. General reaction scheme of synthesis of δ- and ε-HBCD.

(1R,2S,5R,6S,9S,10R)-Hexabromocyclododecane

Crystal data

C12H18Br6	Z = 2
Mr = 641.72	F(000) = 600
Triclinic, P1	Dx = 2.407 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 9.218 (6) Å	Cell parameters from 102 reflections
b = 10.664 (7) Å	θ = 3.5–28°
c = 10.807 (7) Å	µ = 13.58 mm^−1
α = 116.807 (8)°	T = 294 K
β = 96.310 (9)°	Block, colourless
γ = 104.703 (9)°	0.12 × 0.11 × 0.1 mm
V = 885.6 (10) Å^3

Data collection

Bruker APEX CCD area-detector diffractometer	4046 independent reflections
Radiation source: fine-focus sealed tube	2183 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.060
ω scans	θmax = 27.6°, θmin = 2.2°
Absorption correction: ψ scan (SAINT; Bruker, 2001)	h = −11→9
Tmin = 0.194, Tmax = 0.257	k = −10→13
6072 measured reflections	l = −13→14

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)] = 0.045	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.107	H-atom parameters constrained
S = 0.87	w = 1/[σ^2(Fo^2) + (0.0366P)^2] where P = (Fo^2 + 2Fc^2)/3
4046 reflections	(Δ/σ)max = 0.007
165 parameters	Δρmax = 0.66 e Å^−3
0 restraints	Δρmin = −0.79 e Å^−3

Special details

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	0.15295 (11)	0.27503 (12)	0.38667 (10)	0.0522 (3)
Br2	0.42537 (11)	0.58963 (12)	0.68589 (11)	0.0527 (3)
Br5	0.29225 (11)	0.57767 (11)	1.09885 (10)	0.0509 (3)
Br6	−0.01545 (11)	0.26237 (13)	1.05275 (11)	0.0550 (3)
Br9	0.56301 (10)	−0.01812 (12)	0.77553 (10)	0.0475 (3)
Br10	0.25800 (11)	−0.22121 (11)	0.46069 (10)	0.0530 (3)
C1	0.2920 (9)	0.2702 (10)	0.5343 (8)	0.040 (2)
H1	0.3929	0.2794	0.5117	0.048*
C2	0.3175 (9)	0.4033 (9)	0.6823 (9)	0.035 (2)
H2	0.3891	0.3946	0.7496	0.043*
C3	0.1755 (10)	0.4198 (10)	0.7442 (9)	0.042 (2)
H3A	0.1991	0.5251	0.8116	0.051*
H3B	0.0889	0.3912	0.6659	0.051*
C4	0.1214 (9)	0.3341 (10)	0.8186 (8)	0.038 (2)
H4A	0.0892	0.2283	0.7492	0.045*
H4B	0.0303	0.3543	0.8479	0.045*
C5	0.2374 (9)	0.3656 (10)	0.9492 (8)	0.036 (2)
H5	0.3321	0.3535	0.9199	0.043*
C6	0.1904 (9)	0.2662 (10)	1.0140 (9)	0.036 (2)
H6	0.2665	0.3100	1.1059	0.044*
C7	0.1842 (9)	0.1070 (10)	0.9223 (9)	0.039 (2)
H7A	0.1171	0.0652	0.8275	0.047*
H7B	0.1387	0.0480	0.9642	0.047*
C8	0.3428 (9)	0.0945 (10)	0.9078 (8)	0.042 (2)
H8A	0.3892	0.0860	0.9874	0.050*
H8B	0.4083	0.1864	0.9163	0.050*
C9	0.3434 (9)	−0.0364 (10)	0.7682 (9)	0.037 (2)
H9	0.2894	−0.1299	0.7656	0.044*
C10	0.2658 (9)	−0.0404 (9)	0.6350 (8)	0.034 (2)
H10	0.1581	−0.0482	0.6380	0.041*
C11	0.3370 (9)	0.0978 (9)	0.6213 (8)	0.034 (2)
H11A	0.3692	0.1860	0.7157	0.041*
H11B	0.4293	0.0907	0.5871	0.041*
C12	0.2291 (9)	0.1175 (10)	0.5215 (8)	0.037 (2)
H12A	0.1289	0.1050	0.5433	0.044*
H12B	0.2139	0.0407	0.4233	0.044*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0463 (6)	0.0689 (8)	0.0452 (6)	0.0099 (5)	0.0026 (4)	0.0388 (6)
Br2	0.0551 (7)	0.0439 (7)	0.0621 (7)	0.0064 (5)	0.0154 (5)	0.0341 (6)
Br5	0.0488 (6)	0.0401 (7)	0.0510 (6)	0.0162 (5)	0.0066 (5)	0.0134 (5)
Br6	0.0478 (6)	0.0791 (9)	0.0723 (7)	0.0349 (5)	0.0385 (5)	0.0532 (7)
Br9	0.0394 (6)	0.0548 (7)	0.0606 (6)	0.0240 (5)	0.0189 (5)	0.0333 (6)
Br10	0.0492 (6)	0.0407 (7)	0.0491 (6)	0.0092 (5)	0.0144 (5)	0.0092 (5)
C1	0.033 (5)	0.049 (7)	0.033 (5)	0.007 (4)	0.009 (4)	0.021 (5)
C2	0.031 (5)	0.038 (6)	0.040 (5)	0.007 (4)	0.008 (4)	0.024 (5)
C3	0.045 (6)	0.043 (6)	0.050 (6)	0.019 (5)	0.023 (5)	0.028 (5)
C4	0.029 (5)	0.053 (7)	0.033 (5)	0.011 (4)	0.009 (4)	0.025 (5)
C5	0.033 (5)	0.042 (6)	0.023 (5)	0.009 (4)	0.006 (4)	0.010 (4)
C6	0.038 (5)	0.032 (6)	0.033 (5)	0.009 (4)	0.014 (4)	0.012 (5)
C7	0.044 (6)	0.033 (6)	0.045 (6)	0.016 (4)	0.020 (4)	0.019 (5)
C8	0.035 (6)	0.048 (7)	0.037 (5)	0.019 (4)	0.009 (4)	0.015 (5)
C9	0.032 (5)	0.039 (6)	0.054 (6)	0.014 (4)	0.019 (4)	0.032 (5)
C10	0.032 (5)	0.035 (6)	0.032 (5)	0.013 (4)	0.009 (4)	0.014 (4)
C11	0.027 (5)	0.030 (6)	0.035 (5)	0.008 (4)	0.006 (4)	0.008 (4)
C12	0.036 (5)	0.043 (6)	0.027 (5)	0.009 (4)	0.003 (4)	0.017 (4)

Geometric parameters (Å, º)

Br1—C1	1.962 (8)	C5—H5	0.9800
Br2—C2	1.964 (8)	C6—C7	1.512 (11)
Br5—C5	1.981 (8)	C6—H6	0.9800
Br6—C6	1.982 (8)	C7—C8	1.520 (10)
Br9—C9	1.973 (8)	C7—H7A	0.9700
Br10—C10	1.973 (8)	C7—H7B	0.9700
C1—C12	1.518 (12)	C8—C9	1.526 (11)
C1—C2	1.526 (11)	C8—H8A	0.9700
C1—H1	0.9800	C8—H8B	0.9700
C2—C3	1.548 (10)	C9—C10	1.513 (10)
C2—H2	0.9800	C9—H9	0.9800
C3—C4	1.501 (11)	C10—C11	1.534 (11)
C3—H3A	0.9700	C10—H10	0.9800
C3—H3B	0.9700	C11—C12	1.508 (11)
C4—C5	1.519 (10)	C11—H11A	0.9700
C4—H4A	0.9700	C11—H11B	0.9700
C4—H4B	0.9700	C12—H12A	0.9700
C5—C6	1.518 (12)	C12—H12B	0.9700
C12—C1—C2	115.5 (7)	C6—C7—C8	113.2 (7)
C12—C1—Br1	108.2 (5)	C6—C7—H7A	108.9
C2—C1—Br1	110.9 (6)	C8—C7—H7A	108.9
C12—C1—H1	107.3	C6—C7—H7B	108.9
C2—C1—H1	107.3	C8—C7—H7B	108.9
Br1—C1—H1	107.3	H7A—C7—H7B	107.8
C1—C2—C3	118.6 (7)	C7—C8—C9	115.6 (6)
C1—C2—Br2	109.7 (5)	C7—C8—H8A	108.4
C3—C2—Br2	108.8 (6)	C9—C8—H8A	108.4
C1—C2—H2	106.4	C7—C8—H8B	108.4
C3—C2—H2	106.4	C9—C8—H8B	108.4
Br2—C2—H2	106.4	H8A—C8—H8B	107.4
C4—C3—C2	118.6 (8)	C10—C9—C8	113.5 (7)
C4—C3—H3A	107.7	C10—C9—Br9	110.7 (5)
C2—C3—H3A	107.7	C8—C9—Br9	106.5 (5)
C4—C3—H3B	107.7	C10—C9—H9	108.7
C2—C3—H3B	107.7	C8—C9—H9	108.7
H3A—C3—H3B	107.1	Br9—C9—H9	108.7
C3—C4—C5	116.8 (7)	C9—C10—C11	115.6 (7)
C3—C4—H4A	108.1	C9—C10—Br10	110.5 (6)
C5—C4—H4A	108.1	C11—C10—Br10	109.4 (5)
C3—C4—H4B	108.1	C9—C10—H10	107.0
C5—C4—H4B	108.1	C11—C10—H10	107.0
H4A—C4—H4B	107.3	Br10—C10—H10	107.0
C6—C5—C4	117.0 (7)	C12—C11—C10	114.2 (6)
C6—C5—Br5	109.5 (5)	C12—C11—H11A	108.7
C4—C5—Br5	108.9 (6)	C10—C11—H11A	108.7
C6—C5—H5	107.0	C12—C11—H11B	108.7
C4—C5—H5	107.0	C10—C11—H11B	108.7
Br5—C5—H5	107.0	H11A—C11—H11B	107.6
C7—C6—C5	114.4 (7)	C11—C12—C1	112.1 (6)
C7—C6—Br6	108.6 (5)	C11—C12—H12A	109.2
C5—C6—Br6	109.9 (6)	C1—C12—H12A	109.2
C7—C6—H6	107.9	C11—C12—H12B	109.2
C5—C6—H6	107.9	C1—C12—H12B	109.2
Br6—C6—H6	107.9	H12A—C12—H12B	107.9