organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
The hydrogen-bonding scheme in (I) results in two
distinctive submotifs to the unit-cell packing. In the ®rst of
1
1
these, the 4 axis along [001] at x = , y = , with the inversion
2
4
ISSN 0108-2701
point at z = 38, and equivalent locations, generates a closed ring
of four molecules of (I) by way of four O1ÐH1Á Á ÁO1 bonds
(Fig. 2), thus characterized by an R44(8) motif (Bernstein et al.,
1995).
1-Bromo-2,6-dihydroxybenzene
containing R44(8) rings and C(2) helices
In the second submotif, the 41 screw axis at x = , y =
1
1
4
2
generates helical chains of molecules of (I) linked by O2Ð
H2Á Á ÁO2 hydrogen bonds, forming C(2) chains (Fig. 3). Space-
group symmetry results in an equal number of clockwise and
anticlockwise helices, by way of the alternating (with respect
to both [100] and [010]) array of 41 and 43 axes.
Peter Kirsop, John M. D. Storey and William T. A.
Harrison*
Department of Chemistry, University of Aberdeen, Meston Walk, Aberdeen
AB24 3UE, Scotland
Finally, ꢀ±ꢀ stacking interactions are present in (I). The
inversion centre at (14, 41, 41) and equivalent locations generates
pairs of molecules of (I), with a CgÁ Á ÁCgiii separation of
Correspondence e-mail: w.harrison@abdn.ac.uk
Received 22 March 2004
Accepted 23 March 2004
Online 21 April 2004
Ê
3.6397 (12) A [Cg is the centroid of the C1±C6 ring at (0.3348,
1
2
1
2
3
2
0.2915, 0.7669); symmetry code: (iii)
x,
y,
z]. The
best least-squares ring planes for Cg and Cgiii are exactly
ꢀ
Ê
parallel (dihedral angle = 0.0 ) and are separated by 3.470 A.
The lateral displacement of Cgiii relative to the normal from
the Cg best least-squares plane at Cg to the Cgiii best least-
Molecules of the title compound (also known as 2-bromo-
resorcinol), C6H5BrO2, are essentially planar and possess
normal geometrical parameters. The crystal packing is
in¯uenced by OÐHÁ Á ÁO and OÐHÁ Á ÁO/Br hydrogen bonds
and ꢀ±ꢀ stacking interactions, resulting in a distinctive high-
symmetry structure containing R44(8) rings and helical C(2)
chains.
Ê
squares plane is 1.098 A. The unit-cell packing of (I) is shown
in Fig. 4.
Comment
The title compound, (I) (Fig. 1), also known as 2-bromo-
resorcinol, arose during our studies to determine the philicity
of aryl radicals by competitive cyclization (Kirsop et al., 2004).
Figure 1
The asymmetric unit of (I), showing the atom-numbering scheme.
Displacement ellipsoids are drawn at the 50% probability level. H atoms
are shown as small spheres of arbitrary radii and the intramolecular
hydrogen bond is shown as a dashed line.
Compound (I) possesses normal geometrical parameters
Ê
[mean CÐC = 1.386 (2) A, C1ÐBr1 = 1.885 (2) A and mean
Ê
Ê
CÐO = 1.373 (3) A] and, as expected, is essentially planar (for
the non-H atoms, the r.m.s deviation from the best least-
Ê
squares plane is 0.008 A).
As well as van der Waals forces, the crystal packing is
strongly in¯uenced by hydrogen bonding (Table 1). A
hydrogen bond involving atom H2 is bifurcated to an inter-
molecular O and an intramolecular Br acceptor species, and
the donor±acceptor bond-angle sum about atom H2 is 360ꢀ.
The situation involving atom H1 is less clear cut. As well as an
intermolecular O1ÐH1Á Á ÁO1i bond (see Table 1 for symmetry
code), there is also a possible, very long, intermolecular O1Ð
i
Ê
H1Á Á ÁBr1 contact with an HÁ Á ÁBr distance of 3.13 A, although
this was ¯agged as being of questionable signi®cance in a
PLATON (Spek, 2003) analysis of (I). However, the donor±
acceptor bond-angle sum for atoms O1, O1i and Br1i about H1
is 358ꢀ, which suggests that this interaction may have some
signi®cance beyond being merely a packing contact.
Figure 2
Part of the crystal structure of (I), showing a hydrogen-bonded R44(8) ring
and a close ꢀ±ꢀ contact (ring centroids linked by an open line) [symmetry
3
4
1
4
y,
3
3
4
3
4
codes: (i)
1
2
y,
x,
x
,
z; (ii) 14 + y,
z]. H atoms bonded to C atoms and the
x,
z; (iii)
1
x,
4
1
2
1
3
y, z; (iv)
2
2
unit-cell box have been omitted for clarity.
# 2004 International Union of Crystallography o353
Acta Cryst. (2004). C60, o353±o355
DOI: 10.1107/S0108270104006882