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organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Volume 65| Part 2| February 2009| Pages o327-o328
doi:10.1107/S1600536809001408

Redetermination of 2,6-di­meth­oxy­benzoic acid

Gustavo Portalonea*

aChemistry Department, "Sapienza" University of Rome, P.le A. Moro, 5, I-00185 Rome, Italy
*Correspondence e-mail: g.portalone@caspur.it

(Received 2 January 2009; accepted 12 January 2009; online 17 January 2009)

The crystal structure of the title compound, C9H10O4, 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 mol­ecule, as the meth­oxy substituents force the carb­oxy group to be twisted away from the plane of the aromatic ring by 56.12 (9)°. Due to the anti­planar conformation adopted by the OH group, the mol­ecular 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[Swaminathan, S., Vimala, T. M. & Lotter, H. (1976). Acta Cryst. B32, 1897-1900.]); Bryan & White (1982[Bryan, R. F. & White, D. H. (1982). Acta Cryst. B38, 1014-1016.]). For related literature, see: Gopalakrishna & Cartz, 1972[Gopalakrishna, E. M. & Cartz, L. (1972). Acta Cryst. B28, 2917-2924.]; Leiserowitz, 1976[Leiserowitz, L. (1976). Acta Cryst. B32, 775-802.]; Byriel et al., 1991[Byriel, K. A., Lynch, D. E., Smith, G. & Kennard, C. H. L. (1991). Aust. J. Chem. 44, 1459-1464.]; Chen et al., 2007[Chen, Q., Qin, J.-K., Zeng, M.-H. & Ng, S. W. (2007). Acta Cryst. E63, o453-o454.]. For computation of ring patterns formed by hydrogen bonds in crystal structures, see: Etter et al. (1990[Etter, M. C., MacDonald, J. C. & Bernstein, J. (1990). Acta Cryst. B46, 256-262.]); Bernstein et al. (1995[Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555-1573.]); Motherwell et al. (1999[Motherwell, W. D. S., Shields, G. P. & Allen, F. H. (1999). Acta Cryst. B55, 1044-1056.]). For a description of the Cambridge Structural Database, see: Allen (2002[Allen, F. H. (2002). Acta Cryst. B58, 380-388.]).

[Scheme 1]

Experimental

Crystal data

  • C9H10O4

  • Mr = 182.17

  • Orthorhombic, P 21 21 21

  • 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[Oxford Diffraction (2006). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Abingdon, England.]) Tmin = 0.967, Tmax = 0.999

  • 234729 measured reflections

  • 1246 independent reflections

  • 1241 reflections with I > 2σ(I)

  • Rint = 0.039
Refinement

  • R[F2 > 2σ(F2)] = 0.042

  • wR(F2) = 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

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) [-x, y-{\script{1\over 2}}, -z+{\script{1\over 2}}].

Data collection: CrysAlis CCD (Oxford Diffraction, 2006[Oxford Diffraction (2006). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Abingdon, England.]); cell refinement: CrysAlis RED (Oxford Diffraction, 2006[Oxford Diffraction (2006). CrysAlis CCD and CrysAlis RED. Oxford Diffraction Ltd, Abingdon, England.]); data reduction: CrysAlis RED; program(s) used to solve structure: SIR97 (Altomare et al., 1999[Altomare, A., Burla, M. C., Camalli, M., Cascarano, G. L., Giacovazzo, C., Guagliardi, A., Moliterni, A. G. G., Polidori, G. & Spagna, R. (1999). J. Appl. Cryst. 32, 115-119.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: ORTEP-3 (Farrugia, 1997[Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565.]); software used to prepare material for publication: WinGX (Farrugia, 1999[Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837-838.]).

Supporting information

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

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

checkCIF report


Comment top

2,6-Dimethoxybenzoic acid was determined some 30 years ago (Swaminathan et al., 1976) but the final refinement was carried only to R=0.15 and no atomic coordinates were provided. Subsequently, a new X-ray structure determination was reported (Bryan & White, 1982). In this study, 775 unique reflections were collected at ambient temperature on an automatic diffractometer using Cu Kα radiation. Data were corrected for Lp effects, but not for absorption [µ(Cu Kα)= 94 mm-1]. 708 reflections having values significantly above background were used in the block-diagonal least-squares refinement. The final calculations, carried out on a fairly small data set, led to R = 0.035 for 158 refined parameters, a data-to-parameter ratio of 4.5, the maximum shift-to-error in the final cycle being equal to 1/4, and standard deviations of 0.005Å in C—C bond lengths and 0.4° in bond angles.

The asymmetric unit of (I) comprises a non-planar independent molecule, as the methoxy substituents force the carboxy group to be twisted away from the plane of the aromatic ring by 56.12 (9)° (Fig. 1). The values of bond lengths and bond angles are consistent with that reported in the previous determination (Bryan & White, 1982) with the exception of the geometrical parameters of the carboxy group. Analysis of the crystal packing of (I), (Table 1, Fig. 2) shows that the molecular components do not form the conventional dimeric units observed in monocarboylic acids (Leiserowitz, 1976). The structure is stabilized by intermolecular O—H···O interactions of descriptor C(3) (Etter et al., 1990; Bernstein et al., 1995; Motherwell et al., 1999) (Table 1, Fig. 2) between the OH moieties and the carbonyl O atom (O1i) [symmetry code: (i) -x, y - 1/2, -z + 1/2] which link the molecules into endless chains approximately parallel to b. A search of the Cambridge Structural Database (version 5.29; Allen, 2002) for crystal structures containing the o-methoxy benzoic acid residue yields only three structures having the OH group in the unusual antiplanar conformation (Gopalakrishna & Cartz, 1972; Byriel et al., 1991; Chen et al., 2007). For these compounds, the antiplanar conformation is favoured by the formation of intramolecular hydrogen bonding.

Related literature top

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 related literature, see: Allen (2002).

Experimental top

2,6-Dimethoxybenzoic acid (0.1 mmol, Sigma Aldrich at 99% purity) was dissolved in ethanol (95%, 9 mL) and gently heated under reflux for 1 h. After cooling the solution to an ambient temperature, crystals suitable for single-crystal X-ray diffraction were grown by slow evaporation of the solvent after two days.

Refinement top

All H atoms were found in a difference map and then treated as riding atoms, with C—H = 0.97 (phenyl) and 0.96–0.98 Å (methyl); their Uiso values were kept equal to 1.2Ueq(C, phenyl). and to 1.5Ueq(C, methyl). The remaining H atom of the carboxy group was freely refined. In the absence of significant anomalous scattering in this light-atom study, Friedel pairs were merged.

Computing details top

Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell refinement: CrysAlis RED (Oxford Diffraction, 2006); data reduction: CrysAlis RED (Oxford Diffraction, 2006); 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).

Figures top
[Figure 1] Fig. 1. The molecular structure of (I) showing the atom-labelling scheme. Displacements ellipsoids are at the 50% probability level.
[Figure 2] Fig. 2. Crystal packing diagram for (I) viewed approximately down b. All atoms are shown as small spheres of arbitrary radii. For the sake of clarity, H atoms not involved in hydrogen bonding have been omitted. Hydrogen bonding is indicated by dashed lines.
2,6-dimethoxybenzoic acid top
Crystal data top
C9H10O4F(000) = 384
Mr = 182.17Dx = 1.380 Mg m−3
Orthorhombic, P212121Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2abCell parameters from 75565 reflections
a = 7.12255 (13) Åθ = 2.7–32.6°
b = 8.92296 (15) ŵ = 0.11 mm−1
c = 13.79430 (18) ÅT = 298 K
V = 876.69 (2) Å3Tablets, colourless
Z = 40.12 × 0.10 × 0.10 mm
Data collection top
Oxford Diffraction Xcalibur S CCD
diffractometer		1246 independent reflections
Radiation source: Enhance (Mo) X-ray Source1241 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.039
Detector resolution: 16.0696 pixels mm-1θmax = 28.0°, θmin = 2.7°
ω and ϕ scansh = −9→9
Absorption correction: multi-scan
(CrysAlis RED; Oxford Diffraction, 2006)		k = −11→11
Tmin = 0.967, Tmax = 0.999l = −18→18
234729 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.042Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.110H 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 parametersΔρmax = 0.17 e Å−3
0 restraintsΔρmin = −0.20 e Å−3
Crystal data top
C9H10O4V = 876.69 (2) Å3
Mr = 182.17Z = 4
Orthorhombic, P212121Mo Kα radiation
a = 7.12255 (13) ŵ = 0.11 mm−1
b = 8.92296 (15) ÅT = 298 K
c = 13.79430 (18) Å0.12 × 0.10 × 0.10 mm
Data collection top
Oxford Diffraction Xcalibur S CCD
diffractometer		1246 independent reflections
Absorption correction: multi-scan
(CrysAlis RED; Oxford Diffraction, 2006)		1241 reflections with I > 2σ(I)
Tmin = 0.967, Tmax = 0.999Rint = 0.039
234729 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0420 restraints
wR(F2) = 0.110H atoms treated by a mixture of independent and constrained refinement
S = 1.25Δρmax = 0.17 e Å−3
1246 reflectionsΔρmin = −0.20 e Å−3
129 parameters
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/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)*
O30.3469 (2)−0.20799 (17)0.23289 (11)0.0456 (4)
O4−0.1001 (2)0.03782 (19)0.42166 (10)0.0523 (4)
C10.1298 (3)−0.08417 (18)0.33092 (12)0.0313 (4)
C20.3031 (3)−0.1561 (2)0.32308 (14)0.0357 (4)
C30.4215 (3)−0.1652 (3)0.40281 (17)0.0499 (5)
H30.5420−0.21520.39770.067 (8)*
C40.3658 (4)−0.1025 (3)0.48919 (17)0.0561 (6)
H40.4487−0.10920.54480.077 (9)*
C50.1956 (4)−0.0304 (3)0.49927 (14)0.0501 (6)
H50.16050.01440.56070.050 (7)*
C60.0752 (3)−0.0228 (2)0.42020 (13)0.0379 (4)
C70.0046 (3)−0.06772 (19)0.24441 (13)0.0324 (4)
C80.4849 (4)−0.3237 (3)0.2261 (2)0.0635 (7)
H8A0.609−0.28230.24150.095*
H8B0.486−0.3640.16000.095*
H8C0.4545−0.40400.27220.095*
C9−0.1665 (5)0.1023 (4)0.5097 (2)0.0737 (9)
H9A−0.0880.1860.52710.111*
H9B−0.1630.02840.56030.111*
H9C−0.2930.1360.50100.111*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0636 (10)0.0332 (7)0.0383 (7)0.0092 (7)−0.0096 (7)0.0031 (6)
O20.0596 (9)0.0361 (8)0.0508 (8)0.0029 (7)−0.0232 (8)−0.0080 (7)
O30.0458 (8)0.0453 (8)0.0458 (8)0.0111 (7)0.0029 (7)−0.0009 (7)
O40.0604 (10)0.0590 (9)0.0374 (7)0.0120 (8)0.0070 (7)−0.0056 (7)
C10.0411 (9)0.0241 (7)0.0287 (7)−0.0036 (7)−0.0042 (7)0.0020 (6)
C20.0387 (9)0.0293 (8)0.0392 (9)−0.0036 (7)−0.0016 (8)0.0048 (7)
C30.0438 (11)0.0493 (11)0.0566 (12)−0.0013 (10)−0.0146 (10)0.0096 (10)
C40.0653 (15)0.0587 (13)0.0442 (11)−0.0136 (13)−0.0232 (11)0.0081 (11)
C50.0726 (16)0.0481 (11)0.0297 (9)−0.0132 (11)−0.0051 (10)0.0000 (9)
C60.0495 (11)0.0309 (8)0.0333 (8)−0.0061 (8)0.0014 (8)0.0026 (7)
C70.0379 (8)0.0299 (8)0.0295 (7)0.0028 (7)−0.0014 (7)0.0002 (7)
C80.0588 (14)0.0612 (15)0.0704 (16)0.0217 (13)0.0115 (14)0.0042 (14)
C90.083 (2)0.0840 (19)0.0544 (14)0.0126 (18)0.0152 (15)−0.0216 (14)
Geometric parameters (Å, º) top
O1—C71.211 (2)C3—H30.9700
O2—C71.314 (2)C4—C51.379 (4)
O2—H20.87 (4)C4—H40.9700
O3—C21.364 (2)C5—C61.389 (3)
O3—C81.429 (3)C5—H50.9700
O4—C61.361 (3)C8—H8A0.9819
O4—C91.424 (3)C8—H8B0.9819
C1—C21.395 (3)C8—H8C0.9819
C1—C61.403 (2)C9—H9A0.9607
C1—C71.497 (2)C9—H9B0.9607
C2—C31.388 (3)C9—H9C0.9607
C3—C41.375 (4)
C7—O2—H2114 (2)O4—C6—C5125.03 (19)
C2—O3—C8117.56 (18)O4—C6—C1114.99 (17)
C6—O4—C9118.6 (2)C5—C6—C1120.0 (2)
C2—C1—C6119.51 (17)O1—C7—O2118.91 (17)
C2—C1—C7120.69 (16)O1—C7—C1122.81 (16)
C6—C1—C7119.77 (17)O2—C7—C1118.28 (15)
O3—C2—C3124.32 (19)O3—C8—H8A109.5
O3—C2—C1115.42 (16)O3—C8—H8B109.5
C3—C2—C1120.20 (18)H8A—C8—H8B109.5
C4—C3—C2119.2 (2)O3—C8—H8C109.5
C4—C3—H3120.4H8A—C8—H8C109.5
C2—C3—H3120.4H8B—C8—H8C109.5
C3—C4—C5122.1 (2)O4—C9—H9A109.5
C3—C4—H4119.0O4—C9—H9B109.5
C5—C4—H4119.0H9A—C9—H9B109.5
C4—C5—C6119.1 (2)O4—C9—H9C109.5
C4—C5—H5120.5H9A—C9—H9C109.5
C6—C5—H5120.5H9B—C9—H9C109.5
C8—O3—C2—C323.9 (3)C9—O4—C6—C1179.9 (2)
C8—O3—C2—C1−159.0 (2)C4—C5—C6—O4176.4 (2)
C6—C1—C2—O3−177.98 (16)C4—C5—C6—C1−1.9 (3)
C7—C1—C2—O30.1 (2)C2—C1—C6—O4−176.68 (16)
C6—C1—C2—C3−0.7 (3)C7—C1—C6—O45.2 (2)
C7—C1—C2—C3177.33 (18)C2—C1—C6—C51.7 (3)
O3—C2—C3—C4176.9 (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—O155.3 (3)
C3—C4—C5—C61.0 (4)C2—C1—C7—O257.4 (3)
C9—O4—C6—C51.6 (3)C6—C1—C7—O2−124.5 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O2—H2···O1i0.87 (4)1.82 (4)2.681 (2)172 (4)
Symmetry code: (i) −x, y−1/2, −z+1/2.

Experimental details

Crystal data
Chemical formulaC9H10O4
Mr182.17
Crystal system, space groupOrthorhombic, P212121
Temperature (K)298
a, b, c (Å)7.12255 (13), 8.92296 (15), 13.79430 (18)
V (Å3)876.69 (2)
Z4
Radiation typeMo Kα
µ (mm−1)0.11
Crystal size (mm)0.12 × 0.10 × 0.10
Data collection
DiffractometerOxford Diffraction Xcalibur S CCD
diffractometer
Absorption correctionMulti-scan
(CrysAlis RED; Oxford Diffraction, 2006)
Tmin, Tmax0.967, 0.999
No. of measured, independent and
observed [I > 2σ(I)] reflections		234729, 1246, 1241
Rint0.039
(sin θ/λ)max (Å−1)0.660
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.042, 0.110, 1.25
No. of reflections1246
No. of parameters129
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å−3)0.17, −0.20

Computer programs: CrysAlis CCD (Oxford Diffraction, 2006), CrysAlis RED (Oxford Diffraction, 2006), SIR97 (Altomare et al., 1999), SHELXL97 (Sheldrick, 2008), ORTEP-3 (Farrugia, 1997), WinGX (Farrugia, 1999).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O2—H2···O1i0.87 (4)1.82 (4)2.681 (2)172 (4)
Symmetry code: (i) −x, y−1/2, −z+1/2.
 

Acknowledgements

We thank MIUR (Rome) for 2006 financial support of the project `X-ray diffractometry and spectrometry'.

References

First citationAllen, F. H. (2002). Acta Cryst. B58, 380–388.  Web of Science CrossRef CAS IUCr Journals Google Scholar
 First citationAltomare, A., Burla, M. C., Camalli, M., Cascarano, G. L., Giacovazzo, C., Guagliardi, A., Moliterni, A. G. G., Polidori, G. & Spagna, R. (1999). J. Appl. Cryst. 32, 115–119.  Web of Science CrossRef CAS IUCr Journals Google Scholar
 First citationBernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555–1573.  CrossRef CAS Web of Science Google Scholar
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 First citationByriel, K. A., Lynch, D. E., Smith, G. & Kennard, C. H. L. (1991). Aust. J. Chem. 44, 1459–1464.  CrossRef CAS Google Scholar
 First citationChen, Q., Qin, J.-K., Zeng, M.-H. & Ng, S. W. (2007). Acta Cryst. E63, o453–o454.  Web of Science CSD CrossRef IUCr Journals Google Scholar
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 First citationFarrugia, L. J. (1997). J. Appl. Cryst. 30, 565.  CrossRef IUCr Journals Google Scholar
 First citationFarrugia, L. J. (1999). J. Appl. Cryst. 32, 837–838.  CrossRef CAS IUCr Journals Google Scholar
 First citationGopalakrishna, E. M. & Cartz, L. (1972). Acta Cryst. B28, 2917–2924.  CSD CrossRef CAS IUCr Journals Web of Science Google Scholar
 First citationLeiserowitz, L. (1976). Acta Cryst. B32, 775–802.  CrossRef CAS IUCr Journals Web of Science Google Scholar
 First citationMotherwell, W. D. S., Shields, G. P. & Allen, F. H. (1999). Acta Cryst. B55, 1044–1056.  Web of Science CrossRef CAS IUCr Journals Google Scholar
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 First citationSwaminathan, S., Vimala, T. M. & Lotter, H. (1976). Acta Cryst. B32, 1897–1900.  CSD CrossRef CAS IUCr Journals Web of Science Google Scholar

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ISSN: 2056-9890
Volume 65| Part 2| February 2009| Pages o327-o328
doi:10.1107/S1600536809001408
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