Tri­bromo­acetic acid

Acta Cryst.(2003). E59, o619±o621 DOI: 10.1107/S1600536803007268 Jones and Lozano C₂HBr₃O₂

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organic papers

Acta Crystallographica Section E Structure Reports Online

ISSN 1600-5368

Tribromoacetic acid

Peter G. Jones* and Virginia Lozano

Institut fuÈr Anorganische und Analytische Chemie, Technische UniversitaÈt Braunschweig, Postfach 3329, 38023 Braunschweig, Germany

Correspondence e-mail: [email protected]

Key indicators Single-crystal X-ray study T= 133 K

Mean(C±C) = 0.003 AÊ Rfactor = 0.022 wRfactor = 0.053

Data-to-parameter ratio = 26.8

For details of how these key indicators were automatically derived from the article, see http://journals.iucr.org/e.

#2003 International Union of Crystallography Printed in Great Britain ± all rights reserved

The packing of the title compound, C2HBr3O2, involves

regions of hydrogen-bonded carboxylic acid dimers, in turn linked by two contacts of the type Br Br and one Br O.

Comment

We have begun to investigate the structures of tribromo-acetates and therefore decided to determine the structure of the parent acid, tribromoacetic acid. The structure of trichloroacetic acid has recently been reported by Rajagopalet al.(2003).

The molecular structure of tribromoacetic acid, (I), is presented in Fig. 1. Bond lengths and angles may be regarded as normal, in particular the CÐO bond lengths, which show no signs of the disorder sometimes observed in carboxylic acids (for a detailed discussion, see Wilson, 2002). Atom Br2 is approximately synperiplanar to O1.

More interesting features are observed in the packing. Apart from the classical `carboxylic acid dimer' formed by hydrogen bonding, there are three signi®cant contacts involving atom Br1; 3.6284 (5) AÊ to Br2(xÿ1

2, yÿ12, z),

3.6193 (5) AÊ to Br3(ÿxÿ1

2,y+12,ÿz+12), and 3.009 (2) AÊ to

the carbonyl atom O2(xÿ1

2,y+12,z).

The Br Br contacts are established as `type II' in the classi®cation of Pedireddi et al. (1994) by the angles at bromine; 101.25 (7)/167.92 (7) _{for the ®rst and 93.77 (7)/} 167.05 (7) _{for the second. Such contacts are thought to be} associated with a positive region of charge in the extension of the CÐBr vector beyond Br, which can interact with the negative region perpendicular to the CÐBr bond at the other bromine. The somewhat longer Br3 Br3 interaction of 3.8020 (5) AÊ (code:ÿxÿ1

2,yÿ12,ÿz+12), however, has equal

angles at bromine [142.57 (7)_{, equal by symmetry] and such} `type I' contacts are regarded as less energetically favourable. Contacts of the type Br O may be regarded as one form of `halogen bond' (Metrangolo & Resnati, 2001). Although the distance observed here is signi®cantly shorter than the sum of the van der Waals radii (Br = 1.85 AÊ and O = 1.52 AÊ; Bondi, 1964), much shorter values have been observed (down toca

2.7 AÊ, as quoted in the above-mentioned article). Lommerseet al. (1996), in a review of contacts between halogens and oxygen or nitrogen, pointed out that these also tend to be

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Jones and Lozano C₂HBr₃O₂ Acta Cryst.(2003). E59, o619±o621

approximately linear at the halogen [here 157.24 (8)_{], but} show little preferred directionality to the O-atom lone pairs [here the bromine lies 1.964 (5) AÊ out of the C1/C2/O1/O2 plane]. Again, electrostatic forces are thought to play an important role.

The net effect of the contacts can be seen in the packing diagrams. Carboxylic acid dimers occupy the regionsz'0,1

2,

1,etc. Fig. 2 shows the region atz'1

2, with dimer formation

supported by Br1 Br2 and Br1 O2; Br1 Br3 links the CBr3 moieties of successive dimer regions to form double

layers of molecules betweene.g. z'1

2and 1 (Fig. 3).

Experimental

The title material was purchased from Aldrich. Single crystals grew from a solution in dichloromethane/petrol ether (ca 1/5 v/v) on cooling to 255 K.

Crystal data

C2HBr3O2

Mr= 296.76

Monoclinic,C2=c a= 11.1679 (12) AÊ b= 5.7966 (6) AÊ c= 19.821 (2) AÊ = 103.132 (4)

V= 1249.6 (2) AÊ3

Z= 8

Dx= 3.155 Mg mÿ3

MoKradiation Cell parameters from 4624

re¯ections = 3.8±30.5

= 19.26 mmÿ1

T= 133 (2) K Tablet, colourless 0.150.130.04 mm

Data collection

Bruker SMART 1000CCD diffractometer !and'scans

Absorption correction: multi-scan (SADABS; Bruker, 1998) Tmin= 0.268,Tmax= 0.564

9331 measured re¯ections

1823 independent re¯ections 1577 re¯ections withI> 2(I) Rint= 0.037

max= 30.0

h=ÿ15!15 k=ÿ8!8 l=ÿ27!27

Re®nement

Re®nement onF2

R[F2_{> 2(F}2_{)] = 0.022}

wR(F2_{) = 0.053}

S= 1.00 1823 re¯ections 68 parameters

All H-atom parameters re®ned w= 1/[2_(F

o2) + (0.031P)2]

whereP= (Fo2+ 2Fc2)/3

(/)max= 0.001

max= 0.61 e AÊÿ3

min=ÿ0.80 e AÊÿ3

Table 1

Selected geometric parameters (AÊ,_).

Br1ÐC1 1.934 (2) Br2ÐC1 1.929 (3) Br3ÐC1 1.944 (2)

O1ÐC2 1.302 (3) O2ÐC2 1.219 (3) C1ÐC2 1.539 (3)

C2ÐC1ÐBr2 110.56 (17) C2ÐC1ÐBr1 111.01 (17) Br2ÐC1ÐBr1 109.85 (12) C2ÐC1ÐBr3 105.38 (16) Br2ÐC1ÐBr3 110.08 (12)

Br1ÐC1ÐBr3 109.90 (12) O2ÐC2ÐO1 126.2 (2) O2ÐC2ÐC1 121.0 (2) O1ÐC2ÐC1 112.7 (2)

Br2ÐC1ÐC2ÐO2 ÿ16.4 (3)

Table 2

Hydrogen-bonding geometry (AÊ,_).

DÐH A DÐH H A D A DÐH A O1ÐH01 O2i _{0.76 (4) 1.95 (4) 2.691 (3) 162 (4)}

Symmetry code: (i)ÿx;ÿy;1ÿz.

Data collection:SMART(Bruker, 1998); cell re®nement:SAINT (Bruker, 1998); data reduction: SAINT; program(s) used to solve Figure 2

Packing diagram of the title compound viewed perpendicular to theab

plane. Secondary interactions are indicated by dashed lines.

Figure 3

Packing diagram of the title compound viewed perpendicular to thebc

plane. Secondary interactions are indicated by dashed lines. Figure 1

structure:SHELXS97 (Sheldrick, 1990); program(s) used to re®ne structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP (Siemens, 1994); software used to prepare material for publication: SHELXL97.

Financial support from the Fonds der Chemischen Industrie is gratefully acknowledged. VL was supported by the Erasmus scheme. We thank Mr A. Weinkauf for technical assistance.

References

Bondi, A. (1964).J. Phys. Chem.68, 441±451.

Bruker (1998).SMART(Version 5.0),SAINT(Version 4.0) andSADABS (Version 2.0). Bruker AXS Inc., Madison, Wisconsin, USA.

Lommerse, J. P. M., Stone, A. J., Taylor, R. & Allen, F. H. (1996).J. Am. Chem. Soc.118, 3108±3116.

Metrangolo, P. & Resnati, G. (2001).Chem. Eur. J.7, 2511±2519.

Pedireddi, V. R., Reddy, D. S., Goud, B. S., Craig, D. C., Rae, A. D. & Desiraju, G. R. (1994).J. Chem. Soc. Perkin Trans.2, pp. 2353±2360.

Rajagopal, K., Mostad, A., Krishnakumar, R. V., Nandhini, M. S. & Natarajan, S. (2003).Acta Cryst.E59, o316±o318.

Sheldrick, G. M. (1990).Acta Cryst.A46, 467±473.

Sheldrick, G. M. (1997).SHELXL97. University of GoÈttingen, Germany. Siemens (1994).XP. Version 5.03. Siemens Analytical X-ray Instruments Inc.,

Madison, Wisconsin, USA.

Wilson, C. C. (2002).New J. Chem.26, 1733±1739.

Acta Cryst.(2003). E59, o619±o621 Jones and Lozano C₂HBr₃O₂

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Acta Cryst. (2003). E59, o619–o621

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Acta Cryst. (2003). E59, o619–o621 [doi:10.1107/S1600536803007268]

Tribromoacetic acid

Peter G. Jones and Virginia Lozano

S1. Comment

We have begun to investigate the structures of tribromoacetates and therefore decided to determine the structure of the

parent acid, tribromoacetic acid. The structure of trichloracetic acid has recently been reported by Rajagopal et al. (2003).

The molecular structure of tribromoacetic acid, (I), is presented in Fig. 1. Bond lengths and angles may be regarded as

normal, in particular the C—O bond lengths, which show no signs of the disorder sometimes observed in carboxylic

acids (for a detailed discussion, see Wilson, 2002). Atom Br2 is approximately synperiplanar to O1.

More interesting features are observed in the packing. Apart from the classical `carboxylic acid dimer′ formed by

hydrogen bonding, there are three significant contacts involving atom Br1; 3.6284 (5) Å to Br2(x − 1/2, y − 1/2, z),

3.6193 (5) Å to Br3(-x − 1/2, y + 1/2, −z + 1/2), and 3.009 (2) Å to the carbonyl atom O2(x − 1/2, y + 1/2, z).

The Br···Br contacts are established as `type II′ in the classification of Pedireddi et al. (1994) by the angles at bromine;

101.25 (7)/167.92 (7)° for the first and 93.77 (7)/167.05 (7)° for the second. Such contacts are thought to be associated

with a positive region of charge in the extension of the C—Br vector beyond Br, which can interact with the negative

region perpendicular to the C—Br bond at the other bromine. The somewhat longer Br3···Br3 interaction of 3.8020 (5) Å

(code: −x − 1/2, y − 1/2, −z + 1/2), however, has equal angles at bromine [142.57 (7)°, equal by symmetry] and such `type

I′ contacts are regarded as less energetically favourable.

Contacts of the type Br···O may be regarded as one form of `halogen bond′ (Metrangolo & Resnati, 2001). Although the

distance observed here is significantly shorter than the sum of the van der Waals radii (Br = 1.85 Å and O = 1.52 Å;

Bondi, 1964), much shorter values have been observed (down to ca 2.7 Å, as quoted in the above-mentioned article).

Lommerse et al. (1996), in a review of contacts between halogens and oxygen or nitrogen, pointed out that these also

tend to be approximately linear at the halogen [here 157.24 (8)°], but show little preferred directionality to the O-atom

lone pairs [here the bromine lies 1.964 (5) Å out of the C1/C2/O1/O2 plane]. Again, electrostatic forces are thought to

play an important role.

The net effect of the contacts can be seen in the packing diagrams. Carboxylic acid dimers occupy the regions z≈ 0,

1/2, 1, etc. Fig. 2 shows the region at z≈ 1/2, with dimer formation supported by Br1···Br2 and Br1···O2; Br1···Br3 links

the CBr3 moieties of successive dimer regions to form double layers of molecules between e.g. z≈ 1/2 and 1 (Fig. 3).

S2. Experimental

The title material was purchased from Aldrich. Single crystals grew from a solution in dichloromethane/petrol ether (ca

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[image:5.610.126.485.78.348.2]

Acta Cryst. (2003). E59, o619–o621 Figure 1

The molecule of the title compound in the crystal. Ellipsoids represent 50% probability levels. H-atom radii are arbitrary.

Figure 2

Packing diagram of the title compound viewed perpendicular to the xy plane. Secondary interactions are indicated by

[image:5.610.120.489.389.655.2]

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[image:6.610.128.485.66.404.2]

Acta Cryst. (2003). E59, o619–o621 Figure 3

Packing diagram of the title compound viewed perpendicular to the yz plane. Secondary interactions are indicated by

dashed lines.

Tribromoacetic acid

Crystal data

C2HBr3O2

Mr = 296.76 Monoclinic, C2/c a = 11.1679 (12) Å b = 5.7966 (6) Å c = 19.821 (2) Å β = 103.132 (4)° V = 1249.6 (2) Å3

Z = 8

F(000) = 1072 Dx = 3.155 Mg m−3

Mo Kα radiation, λ = 0.71073 Å Cell parameters from 4624 reflections θ = 3.8–30.5°

µ = 19.26 mm−1

T = 133 K Tablet, colourless 0.15 × 0.13 × 0.04 mm

Data collection

Bruker SMART 1000 CCD diffractometer

Radiation source: fine-focus sealed tube Graphite monochromator

Detector resolution: 8.192 pixels mm-1

ω and φ scans

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Acta Cryst. (2003). E59, o619–o621 θmax = 30.0°, θmin = 2.1°

h = −15→15

k = −8→8 l = −27→27

Refinement

Refinement on F2 Least-squares matrix: full R[F2 _{> 2σ(F}2_{)] = 0.022}

wR(F2_{) = 0.053}

S = 1.00 1823 reflections 68 parameters 0 restraints

Primary atom site location: structure-invariant direct methods

Secondary atom site location: difference Fourier map

Hydrogen site location: inferred from neighbouring sites

All H-atom parameters refined w = 1/[σ2_(F

o2) + (0.031P)2] where P = (Fo2 + 2Fc2)/3 (Δ/σ)max = 0.001

Δρmax = 0.61 e Å−3 Δρmin = −0.80 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.

Non-bonded contacts: Distances

3.6284 (0.0005) Br1 - Br2_$2 3.6193 (0.0005) Br1 - Br3_$3 3.8020 (0.0005) Br3 - Br3_$4 3.0091 (0.0020) Br1 - O2_$5 3.4620 (0.0022) Br1 - O1_$6

Angles

101.25 (0.07) C1 - Br1 - Br2_$2 167.92 (0.07) Br1 - Br2_$2 - C1_$2 93.77 (0.07) C1 - Br1 - Br3_$3 161.05 (0.07) Br1 - Br3_$3 - C1_$3 142.57 (0.07) C1 - Br3 - Br3_$4 157.24 (0.08) C1 - Br1 - O2_$5 129.94 (0.17) Br1 - O2_$5 - C2_$5 108.12 (0.08) C1 - Br1 - O1_$6 124.07 (0.16) Br1 - O1_$6 - C2_$6

Operators for generating equivalent atoms:

$2 x − 1/2, y − 1/2, z $3 − x − 1/2, y + 1/2, −z + 1/2 $4 − x − 1/2, y − 1/2, −z + 1/2 $5 x − 1/2, y + 1/2, z $6 x, y + 1, z Refinement. Refinement of F2 _{against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F}2_, conventional R-factors R are based on F, with F set to zero for negative F2_{. The threshold expression of F}2 _{> σ(F}2_{) 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 (Å2₎

x y z Uiso*/Ueq

Br1 −0.24614 (2) 0.57970 (4) 0.389915 (13) 0.01850 (7)

Br2 0.02550 (3) 0.62438 (5) 0.369499 (15) 0.02254 (8)

Br3 −0.14928 (3) 0.22989 (5) 0.291161 (13) 0.02456 (8)

O1 −0.14986 (18) 0.1241 (4) 0.45092 (11) 0.0219 (4)

H01 −0.134 (4) 0.014 (7) 0.472 (2) 0.046 (13)*

O2 0.04944 (17) 0.2079 (3) 0.45893 (10) 0.0213 (4)

C1 −0.1044 (2) 0.4116 (4) 0.37556 (12) 0.0148 (5)

C2 −0.0599 (2) 0.2358 (4) 0.43403 (12) 0.0155 (5)

Atomic displacement parameters (Å2₎

U11 _U22 _U33 _U12 _U13 _U23

Br1 0.01605 (13) 0.01810 (13) 0.02177 (13) 0.00315 (9) 0.00519 (10) 0.00137 (9)

Br2 0.01902 (15) 0.02053 (14) 0.02938 (15) −0.00299 (9) 0.00825 (11) 0.00536 (10)

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Acta Cryst. (2003). E59, o619–o621

O1 0.0154 (10) 0.0233 (11) 0.0261 (10) −0.0013 (8) 0.0029 (8) 0.0101 (8)

O2 0.0155 (10) 0.0257 (10) 0.0226 (9) 0.0015 (8) 0.0042 (8) 0.0081 (8)

C1 0.0143 (12) 0.0155 (12) 0.0146 (11) 0.0000 (9) 0.0033 (9) 0.0010 (9)

C2 0.0185 (13) 0.0161 (12) 0.0123 (11) 0.0000 (9) 0.0041 (9) −0.0010 (9)

Geometric parameters (Å, º)

Br1—C1 1.934 (2) O2—C2 1.219 (3)

Br2—C1 1.929 (3) C1—C2 1.539 (3)

Br3—C1 1.944 (2) O1—H01 0.76 (4)

O1—C2 1.302 (3)

C2—C1—Br2 110.56 (17) Br1—C1—Br3 109.90 (12)

C2—C1—Br1 111.01 (17) O2—C2—O1 126.2 (2)

Br2—C1—Br1 109.85 (12) O2—C2—C1 121.0 (2)

C2—C1—Br3 105.38 (16) O1—C2—C1 112.7 (2)

Br2—C1—Br3 110.08 (12) C2—O1—H01 118 (3)

Br2—C1—C2—O2 −16.4 (3) Br2—C1—C2—O1 165.00 (18)

Br1—C1—C2—O2 −138.6 (2) Br1—C1—C2—O1 42.8 (3)

Br3—C1—C2—O2 102.5 (2) Br3—C1—C2—O1 −76.1 (2)

Hydrogen-bond geometry (Å, º)

D—H···A D—H H···A D···A D—H···A

O1—H01···O2i _{0.76 (4) 1.95 (4) 2.691 (3) 162 (4)}