Redetermination of 2,6-dimethoxy-benzoic acid.

The crystal structure of the title compound, C(9)H(10)O(4), was first reported by Swaminathan, Vimala & Lotter [Acta Cryst. (1976), B32, 1897-1900]. It has been re-examined, improving the precision of the derived geometric parameters. The asymmetric unit comprises a non-planar independent mol-ecule, as the meth-oxy substituents force the carb-oxy group to be twisted away from the plane of the aromatic ring by 56.12 (9)°. Due to the anti-planar conformation adopted by the OH group, the mol-ecular components do not form the conventional dimeric units, but are associated in the crystal in chains stabilized by linear O-H⋯O hydrogen bonds, involving the OH groups and the carbonyl O atoms, which form C(3) motifs.

Related literature

For previous structure determinations, see: Swaminathan et al. (1976 ▶); Bryan & White (1982 ▶). For related literature, see: Gopalakrishna & Cartz, 1972 ▶; Leiserowitz, 1976 ▶; Byriel et al., 1991 ▶; Chen et al., 2007 ▶. For computation of ring patterns formed by hydrogen bonds in crystal structures, see: Etter et al. (1990 ▶); Bernstein et al. (1995 ▶); Motherwell et al. (1999 ▶). For a description of the Cambridge Structural Database, see: Allen (2002 ▶).

Experimental

Crystal data

C9H10O4

M = 182.17

Orthorhombic,

a = 7.12255 (13) Å

b = 8.92296 (15) Å

c = 13.79430 (18) Å

V = 876.69 (2) Å3

Z = 4

Mo Kα radiation

μ = 0.11 mm−1

T = 298 (2) K

0.12 × 0.10 × 0.10 mm

Data collection

Oxford Diffraction Xcalibur S CCD diffractometer

Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006 ▶) T min = 0.967, T max = 0.999

234729 measured reflections

1246 independent reflections

1241 reflections with I > 2σ(I)

R int = 0.039

Refinement

R[F 2 > 2σ(F 2)] = 0.042

wR(F 2) = 0.110

S = 1.25

1246 reflections

129 parameters

H atoms treated by a mixture of independent and constrained refinement

Δρmax = 0.17 e Å−3

Δρmin = −0.20 e Å−3

Data collection: CrysAlis CCD (Oxford Diffraction, 2006 ▶); cell refinement: CrysAlis RED (Oxford Diffraction, 2006 ▶); data reduction: CrysAlis RED; program(s) used to solve structure: SIR97 (Altomare et al., 1999 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 (Farrugia, 1997 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶).

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809001408/kp2203sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809001408/kp2203Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

C9H10O4	F(000) = 384
Mr = 182.17	Dx = 1.380 Mg m−3
Orthorhombic, P212121	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 75565 reflections
a = 7.12255 (13) Å	θ = 2.7–32.6°
b = 8.92296 (15) Å	µ = 0.11 mm−1
c = 13.79430 (18) Å	T = 298 K
V = 876.69 (2) Å3	Tablets, colourless
Z = 4	0.12 × 0.10 × 0.10 mm

Oxford Diffraction Xcalibur S CCD diffractometer	1246 independent reflections
Radiation source: Enhance (Mo) X-ray Source	1241 reflections with I > 2σ(I)
graphite	Rint = 0.039
Detector resolution: 16.0696 pixels mm-1	θmax = 28.0°, θmin = 2.7°
ω and φ scans	h = −9→9
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006)	k = −11→11
Tmin = 0.967, Tmax = 0.999	l = −18→18
234729 measured reflections

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.042	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.110	H atoms treated by a mixture of independent and constrained refinement
S = 1.25	w = 1/[σ2(Fo2) + (0.059P)2 + 0.1016P] where P = (Fo2 + 2Fc2)/3
1246 reflections	(Δ/σ)max < 0.001
129 parameters	Δρmax = 0.17 e Å−3
0 restraints	Δρmin = −0.20 e Å−3

Experimental. CrysAlis RED (Oxford Diffraction, 2008) Version 1.171.32.15 (release 10-01-2008 CrysAlis171 .NET) (compiled Jan 10 2008,16:37:18) Empirical absorption correction using spherical harmonics, implemented in SCALE3 ABSPACK scaling algorithm.

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.

	x	y	z	Uiso*/Ueq
O1	−0.0502 (3)	0.05267 (15)	0.21547 (10)	0.0450 (4)
O2	−0.0480 (3)	−0.18967 (17)	0.19834 (12)	0.0488 (4)
H2	−0.005 (6)	−0.272 (4)	0.224 (2)	0.080 (11)*
O3	0.3469 (2)	−0.20799 (17)	0.23289 (11)	0.0456 (4)
O4	−0.1001 (2)	0.03782 (19)	0.42166 (10)	0.0523 (4)
C1	0.1298 (3)	−0.08417 (18)	0.33092 (12)	0.0313 (4)
C2	0.3031 (3)	−0.1561 (2)	0.32308 (14)	0.0357 (4)
C3	0.4215 (3)	−0.1652 (3)	0.40281 (17)	0.0499 (5)
H3	0.5420	−0.2152	0.3977	0.067 (8)*
C4	0.3658 (4)	−0.1025 (3)	0.48919 (17)	0.0561 (6)
H4	0.4487	−0.1092	0.5448	0.077 (9)*
C5	0.1956 (4)	−0.0304 (3)	0.49927 (14)	0.0501 (6)
H5	0.1605	0.0144	0.5607	0.050 (7)*
C6	0.0752 (3)	−0.0228 (2)	0.42020 (13)	0.0379 (4)
C7	0.0046 (3)	−0.06772 (19)	0.24441 (13)	0.0324 (4)
C8	0.4849 (4)	−0.3237 (3)	0.2261 (2)	0.0635 (7)
H8A	0.609	−0.2823	0.2415	0.095*
H8B	0.486	−0.364	0.1600	0.095*
H8C	0.4545	−0.4040	0.2722	0.095*
C9	−0.1665 (5)	0.1023 (4)	0.5097 (2)	0.0737 (9)
H9A	−0.088	0.186	0.5271	0.111*
H9B	−0.163	0.0284	0.5603	0.111*
H9C	−0.293	0.136	0.5010	0.111*

	U11	U22	U33	U12	U13	U23
O1	0.0636 (10)	0.0332 (7)	0.0383 (7)	0.0092 (7)	−0.0096 (7)	0.0031 (6)
O2	0.0596 (9)	0.0361 (8)	0.0508 (8)	0.0029 (7)	−0.0232 (8)	−0.0080 (7)
O3	0.0458 (8)	0.0453 (8)	0.0458 (8)	0.0111 (7)	0.0029 (7)	−0.0009 (7)
O4	0.0604 (10)	0.0590 (9)	0.0374 (7)	0.0120 (8)	0.0070 (7)	−0.0056 (7)
C1	0.0411 (9)	0.0241 (7)	0.0287 (7)	−0.0036 (7)	−0.0042 (7)	0.0020 (6)
C2	0.0387 (9)	0.0293 (8)	0.0392 (9)	−0.0036 (7)	−0.0016 (8)	0.0048 (7)
C3	0.0438 (11)	0.0493 (11)	0.0566 (12)	−0.0013 (10)	−0.0146 (10)	0.0096 (10)
C4	0.0653 (15)	0.0587 (13)	0.0442 (11)	−0.0136 (13)	−0.0232 (11)	0.0081 (11)
C5	0.0726 (16)	0.0481 (11)	0.0297 (9)	−0.0132 (11)	−0.0051 (10)	0.0000 (9)
C6	0.0495 (11)	0.0309 (8)	0.0333 (8)	−0.0061 (8)	0.0014 (8)	0.0026 (7)
C7	0.0379 (8)	0.0299 (8)	0.0295 (7)	0.0028 (7)	−0.0014 (7)	0.0002 (7)
C8	0.0588 (14)	0.0612 (15)	0.0704 (16)	0.0217 (13)	0.0115 (14)	0.0042 (14)
C9	0.083 (2)	0.0840 (19)	0.0544 (14)	0.0126 (18)	0.0152 (15)	−0.0216 (14)

O1—C7	1.211 (2)	C3—H3	0.9700
O2—C7	1.314 (2)	C4—C5	1.379 (4)
O2—H2	0.87 (4)	C4—H4	0.9700
O3—C2	1.364 (2)	C5—C6	1.389 (3)
O3—C8	1.429 (3)	C5—H5	0.9700
O4—C6	1.361 (3)	C8—H8A	0.9819
O4—C9	1.424 (3)	C8—H8B	0.9819
C1—C2	1.395 (3)	C8—H8C	0.9819
C1—C6	1.403 (2)	C9—H9A	0.9607
C1—C7	1.497 (2)	C9—H9B	0.9607
C2—C3	1.388 (3)	C9—H9C	0.9607
C3—C4	1.375 (4)
C7—O2—H2	114 (2)	O4—C6—C5	125.03 (19)
C2—O3—C8	117.56 (18)	O4—C6—C1	114.99 (17)
C6—O4—C9	118.6 (2)	C5—C6—C1	120.0 (2)
C2—C1—C6	119.51 (17)	O1—C7—O2	118.91 (17)
C2—C1—C7	120.69 (16)	O1—C7—C1	122.81 (16)
C6—C1—C7	119.77 (17)	O2—C7—C1	118.28 (15)
O3—C2—C3	124.32 (19)	O3—C8—H8A	109.5
O3—C2—C1	115.42 (16)	O3—C8—H8B	109.5
C3—C2—C1	120.20 (18)	H8A—C8—H8B	109.5
C4—C3—C2	119.2 (2)	O3—C8—H8C	109.5
C4—C3—H3	120.4	H8A—C8—H8C	109.5
C2—C3—H3	120.4	H8B—C8—H8C	109.5
C3—C4—C5	122.1 (2)	O4—C9—H9A	109.5
C3—C4—H4	119.0	O4—C9—H9B	109.5
C5—C4—H4	119.0	H9A—C9—H9B	109.5
C4—C5—C6	119.1 (2)	O4—C9—H9C	109.5
C4—C5—H5	120.5	H9A—C9—H9C	109.5
C6—C5—H5	120.5	H9B—C9—H9C	109.5
C8—O3—C2—C3	23.9 (3)	C9—O4—C6—C1	179.9 (2)
C8—O3—C2—C1	−159.0 (2)	C4—C5—C6—O4	176.4 (2)
C6—C1—C2—O3	−177.98 (16)	C4—C5—C6—C1	−1.9 (3)
C7—C1—C2—O3	0.1 (2)	C2—C1—C6—O4	−176.68 (16)
C6—C1—C2—C3	−0.7 (3)	C7—C1—C6—O4	5.2 (2)
C7—C1—C2—C3	177.33 (18)	C2—C1—C6—C5	1.7 (3)
O3—C2—C3—C4	176.9 (2)	C7—C1—C6—C5	−176.37 (17)
C1—C2—C3—C4	−0.1 (3)	C2—C1—C7—O1	−122.8 (2)
C2—C3—C4—C5	−0.1 (4)	C6—C1—C7—O1	55.3 (3)
C3—C4—C5—C6	1.0 (4)	C2—C1—C7—O2	57.4 (3)
C9—O4—C6—C5	1.6 (3)	C6—C1—C7—O2	−124.5 (2)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2···O1i	0.87 (4)	1.82 (4)	2.681 (2)	172 (4)

Table 1

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O2—H2⋯O1i	0.87 (4)	1.82 (4)	2.681 (2)	172 (4)

Symmetry code: (i) .