(2-Methyl­phenoxy)­acetic acid

Cox, P.J.; Hickey, G.

doi:10.1107/S1600536804007883

organic compounds

CRYSTALLOGRAPHIC
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ISSN: 2056-9890

Volume 60| Part 5| May 2004| Pages o771-o773

https://doi.org/10.1107/S1600536804007883

(2-Methylphenoxy)acetic acid

Philip J. Cox ^a ^* and Geraldine Hickey ^a

^aSchool of Pharmacy, The Robert Gordon University, Schoolhill, Aberdeen AB10 1FR, Scotland
^*Correspondence e-mail: p.j.cox@rgu.ac.uk

(Received 24 March 2004; accepted 31 March 2004; online 17 April 2004)

Dimeric hydrogen bonding is present in the crystal structure of (2-methylphenoxy)acetic acid, C₉H₁₀O₃, involving the carboxylate groups of centrosymmetrically related pairs of molecules. The structure is further stabilized by C—H⋯O hydrogen bonding.

Comment

The title compound, (I), also known as (o-tolyloxy)acetic acid, has been described as an expectorant (Negwer, 1996 ), and several phenoxyacetic acid compounds are used as herbicides (Cserhati & Forgacs, 1998 ).

The atomic arrangement in (I) is shown in Fig. 1 and selected geometric parameters are given in Table 1. Apart from the H atoms, the molecule is essentially planar and the torsion angle with the greatest deviation from 0, or $[\pm]$ 180°, is C2—O1—C7—C8 = 175.6 (2)°.

Carboxylic acids normally form dimers or catemers and here, as expected for a simple monocarboxylic acid, dimers are formed by intermolecular hydrogen bonding involving the carboxylate groups. The pairs of molecules forming the dimers are related by a centre of symmetry and details of the hydrogen bonding are given in Table 2. As well as the dimeric R₂²(8) motif, a weak C—H⋯O contact (Table 2) is present and this links two molecules about a centre of symmetry in an R₂²(14) formation (Fig. 2). Hence, atom O2 acts as both a donor and an acceptor. Indications of C—H⋯π bonding (Table 2) are also present as H7A is close to the centroid (Cg1) of the aromatic ring.

There are many similar examples of dimer formation involving carboxylate groups e.g. phenylacetic acid (Hodgson & Asplund, 1991 ) and 2,4,5-trimethylbenzoic acid (Barcon et al., 1997 ). The solid-state structures of related compounds, viz. (4-methylphenoxy)acetic acid (Kumar & Rao, 1982 ) and 3-(2-hydroxyphenyl)propionic acid (Begum et al., 1992 ), have also been determined.

Figure 1
The atomic arrangement in the molecule of (I

), with the the atom-numbering scheme and 50% probability displacement ellipsoids.

Figure 2
A partial packing diagram of (I

), showing R₂²(8) and R₂²(14) ring formations. [Symmetry codes: (*) −1 − x, −y, 1 − z; (#) −x, −y, 2 − z.]

Experimental

The title compound was obtained from Aldrich and was recrystallized from a mixture of methanol and ethanol.

Crystal data

C₉H₁₀O₃
M_r = 166.17
Monoclinic, P2₁/c
a = 5.1062 (5) Å
b = 22.352 (2) Å
c = 7.4014 (9) Å
β = 108.235 (5)°
V = 802.33 (14) Å³
Z = 4
D_x = 1.376 Mg m⁻³
Mo Kα radiation
Cell parameters from 2909 reflections
θ = 3.0–27.5°
μ = 0.10 mm⁻¹
T = 150 (2) K
Plate, colourless
0.40 × 0.24 × 0.06 mm

Data collection

Enraf–Nonius KappaCCD area detector
φ and ω scans
Absorption correction: multi-scan (SORTAV; Blessing, 1995 ) T_min = 0.97, T_max = 0.99
2908 measured reflections
1304 independent reflections
1006 reflections with I > 2σ(I)
R_int = 0.055
θ_max = 27.5°
h = −6 → 5
k = −28 → 29
l = −9 → 9

Refinement

Refinement on F²
R[F² > 2σ(F²)] = 0.078
wR(F²) = 0.230
S = 1.04
1304 reflections
115 parameters
H atoms treated by a mixture of independent and constrained refinement
w = 1/[σ²(F_o²) + (0.1765P)²] where P = (F_o² + 2F_c²)/3
(Δ/σ)_max < 0.001
Δρ_max = 0.36 e Å⁻³
Δρ_min = −0.53 e Å⁻³
Extinction correction: SHELXL97
Extinction coefficient: 0.07 (2)

Table 1
Selected geometric parameters (Å, °)

O1—C1	1.381 (3)
O1—C7	1.415 (3)
O2—C8	1.322 (3)
O3—C8	1.219 (3)

C1—O1—C7	116.32 (19)
O1—C1—C2	114.7 (2)
O3—C8—O2	124.4 (2)
O3—C8—C7	124.8 (2)
O2—C8—C7	110.8 (2)

O1—C1—C2—C9	3.7 (4)
C1—O1—C7—C8	175.6 (2)

Table 2
Hydrogen-bonding geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O2—H2⋯O3ⁱ	0.93 (4)	1.69 (4)	2.618 (3)	172 (4)
C6—H6⋯O2ⁱⁱ	0.95	2.56	3.505 (3)	175
C7—H7A⋯Cg1ⁱⁱⁱ	0.99	2.60	3.37	134
Symmetry codes: (i) -1-x,-y,1-z; (ii) -x,-y,2-z; (iii) x-1,y,z. Cg1 is the centroid of the aromatic ring.

The crystal diffracted very weakly and decomposed during data collection, hence data completeness is only 71%. The hydroxy (O2) H atom was refined isotropically. The C—H H atoms were allowed to ride on their attached C atoms: C—H distances were 0.95 Å (aromatic), 0.99 Å (methylene) and 0.98 Å (methyl), and U_iso(H) = 1.2U_eq(non-methyl C) or 1.4U_eq(methyl C).

Data collection: DENZO (Otwinowski & Minor, 1997 ) and COLLECT (Hooft, 1998 ); cell refinement: DENZO and COLLECT; data reduction: DENZO and COLLECT; program(s) used to solve structure: SIR97 (Altomare et al., 1999 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997 ); molecular graphics: PLATON (Spek, 2003 ); software used to prepare material for publication: WinGX (Farrugia, 1999 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: https://doi.org/10.1107/S1600536804007883/su6091sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536804007883/su6091Isup2.hkl

Computing details top

Data collection: DENZO (Otwinowski & Minor, 1997) and COLLECT (Hooft, 1998); cell refinement: DENZO and COLLECT; data reduction: DENZO and COLLECT; program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2002); software used to prepare material for publication: WinGX (Farrugia, 1999).

(2-Methylphenoxy)acetic acid top

Crystal data top

C₉H₁₀O₃	F(000) = 352
M_r = 166.17	D_x = 1.376 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 2909 reflections
a = 5.1062 (5) Å	θ = 3.0–27.5°
b = 22.352 (2) Å	µ = 0.10 mm⁻¹
c = 7.4014 (9) Å	T = 150 K
β = 108.235 (5)°	Plate, colourless
V = 802.33 (14) Å³	0.40 × 0.24 × 0.06 mm
Z = 4

Data collection top

Enraf–Nonius KappaCCD area detector diffractometer	1304 independent reflections
Radiation source: Enraf–Nonius FR591 rotating anode	1006 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.055
Detector resolution: 9.091 pixels mm^-1	θ_max = 27.5°, θ_min = 3.0°
φ and ω scans	h = −6→5
Absorption correction: multi-scan (SORTAV; Blessing, 1995)	k = −28→29
T_min = 0.97, T_max = 0.99	l = −9→9
2908 measured reflections

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.078	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.230	w = 1/[σ²(F_o²) + (0.1765P)²] where P = (F_o² + 2F_c²)/3
S = 1.04	(Δ/σ)_max < 0.001
1304 reflections	Δρ_max = 0.36 e Å⁻³
115 parameters	Δρ_min = −0.53 e Å⁻³
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.07 (2)

Special details top

Experimental. Please note cell_measurement_ fields are not relevant to area detector data, the entire data set is used to refine the cell, which is indexed from all observed reflections in a 10 degree phi range.

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

	x	y	z	U_iso*/U_eq
O1	0.2301 (3)	0.09458 (8)	0.7120 (2)	0.0268 (6)
O2	−0.2795 (4)	−0.00989 (9)	0.7344 (3)	0.0307 (7)
H2	−0.443 (7)	−0.022 (2)	0.645 (5)	0.062 (12)*
O3	−0.2447 (3)	0.04691 (8)	0.4924 (3)	0.0267 (6)
C1	0.4626 (5)	0.12234 (11)	0.8299 (4)	0.0240 (7)
C2	0.5808 (5)	0.16514 (11)	0.7399 (4)	0.0256 (7)
C3	0.8208 (6)	0.19291 (12)	0.8493 (4)	0.0288 (8)
H3	0.9040	0.2221	0.7915	0.035*
C4	0.9440 (5)	0.17961 (12)	1.0406 (4)	0.0278 (7)
H4	1.1116	0.1984	1.1112	0.033*
C5	0.8177 (5)	0.13824 (12)	1.1272 (4)	0.0268 (7)
H5	0.8958	0.1296	1.2589	0.032*
C6	0.5776 (5)	0.10956 (11)	1.0210 (4)	0.0246 (7)
H6	0.4924	0.0811	1.0799	0.030*
C7	0.1007 (5)	0.05243 (11)	0.7989 (4)	0.0247 (7)
H7A	0.0566	0.0714	0.9067	0.030*
H7B	0.2272	0.0185	0.8489	0.030*
C8	−0.1568 (5)	0.03024 (11)	0.6572 (4)	0.0236 (7)
C9	0.4458 (6)	0.18060 (13)	0.5338 (4)	0.0334 (8)
H9A	0.5338	0.2163	0.5017	0.047*
H9B	0.2495	0.1886	0.5114	0.047*
H9C	0.4662	0.1470	0.4541	0.047*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0295 (11)	0.0223 (10)	0.0275 (13)	−0.0086 (7)	0.0072 (9)	0.0024 (8)
O2	0.0338 (12)	0.0250 (10)	0.0308 (13)	−0.0092 (8)	0.0066 (10)	0.0048 (8)
O3	0.0329 (12)	0.0200 (9)	0.0258 (13)	−0.0051 (7)	0.0070 (10)	0.0006 (7)
C1	0.0270 (14)	0.0150 (12)	0.0297 (16)	0.0000 (9)	0.0083 (12)	−0.0019 (10)
C2	0.0322 (15)	0.0170 (12)	0.0280 (15)	−0.0010 (10)	0.0100 (12)	−0.0004 (11)
C3	0.0372 (15)	0.0157 (12)	0.0344 (18)	−0.0038 (10)	0.0126 (13)	−0.0005 (11)
C4	0.0282 (14)	0.0192 (13)	0.0331 (18)	−0.0046 (9)	0.0055 (13)	−0.0062 (11)
C5	0.0305 (15)	0.0225 (14)	0.0257 (15)	0.0002 (10)	0.0063 (12)	−0.0035 (11)
C6	0.0278 (14)	0.0182 (12)	0.0274 (16)	−0.0001 (9)	0.0081 (12)	0.0002 (11)
C7	0.0341 (16)	0.0164 (12)	0.0261 (15)	−0.0045 (9)	0.0133 (13)	−0.0001 (10)
C8	0.0310 (14)	0.0147 (12)	0.0268 (16)	−0.0006 (9)	0.0114 (13)	−0.0005 (10)
C9	0.0412 (16)	0.0241 (14)	0.0319 (19)	−0.0037 (11)	0.0072 (14)	0.0070 (11)

Geometric parameters (Å, º) top

O1—C1	1.381 (3)	C4—C5	1.393 (4)
O1—C7	1.415 (3)	C4—H4	0.9500
O2—C8	1.322 (3)	C5—C6	1.389 (3)
O2—H2	0.93 (4)	C5—H5	0.9500
O3—C8	1.219 (3)	C6—H6	0.9500
C1—C6	1.381 (4)	C7—C8	1.487 (3)
C1—C2	1.405 (4)	C7—H7A	0.9900
C2—C3	1.386 (4)	C7—H7B	0.9900
C2—C9	1.504 (4)	C9—H9A	0.9800
C3—C4	1.390 (4)	C9—H9B	0.9800
C3—H3	0.9500	C9—H9C	0.9800

C1—O1—C7	116.32 (19)	C1—C6—H6	120.0
C8—O2—H2	109 (2)	C5—C6—H6	120.0
O1—C1—C6	124.1 (2)	O1—C7—C8	109.7 (2)
O1—C1—C2	114.7 (2)	O1—C7—H7A	109.7
C6—C1—C2	121.2 (2)	C8—C7—H7A	109.7
C3—C2—C1	117.4 (2)	O1—C7—H7B	109.7
C3—C2—C9	122.0 (2)	C8—C7—H7B	109.7
C1—C2—C9	120.6 (2)	H7A—C7—H7B	108.2
C2—C3—C4	122.4 (3)	O3—C8—O2	124.4 (2)
C2—C3—H3	118.8	O3—C8—C7	124.8 (2)
C4—C3—H3	118.8	O2—C8—C7	110.8 (2)
C3—C4—C5	118.9 (2)	C2—C9—H9A	109.5
C3—C4—H4	120.5	C2—C9—H9B	109.5
C5—C4—H4	120.5	H9A—C9—H9B	109.5
C6—C5—C4	120.0 (3)	C2—C9—H9C	109.5
C6—C5—H5	120.0	H9A—C9—H9C	109.5
C4—C5—H5	120.0	H9B—C9—H9C	109.5
C1—C6—C5	120.1 (3)

C7—O1—C1—C6	2.6 (4)	C2—C3—C4—C5	−2.0 (4)
C7—O1—C1—C2	−178.2 (2)	C3—C4—C5—C6	2.1 (4)
O1—C1—C2—C3	−177.6 (2)	O1—C1—C6—C5	177.7 (2)
C6—C1—C2—C3	1.5 (4)	C2—C1—C6—C5	−1.4 (4)
O1—C1—C2—C9	3.7 (4)	C4—C5—C6—C1	−0.5 (4)
C6—C1—C2—C9	−177.2 (2)	C1—O1—C7—C8	175.6 (2)
C1—C2—C3—C4	0.2 (4)	O1—C7—C8—O3	−1.3 (4)
C9—C2—C3—C4	178.8 (3)	O1—C7—C8—O2	179.1 (2)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2···O3ⁱ	0.93 (4)	1.69 (4)	2.618 (3)	172 (4)
C6—H6···O2ⁱⁱ	0.95	2.56	3.505 (3)	175
C7—H7A···Cg1ⁱⁱⁱ	0.99	2.60	3.37	134

Symmetry codes: (i) −x−1, −y, −z+1; (ii) −x, −y, −z+2; (iii) x−1, y, z.

Acknowledgements

We thank the EPSRC for use of the National Crystallographic Service at Southampton University (X-ray data collection) and for the use of the Chemical Database Service at Daresbury (Fletcher et al., 1996 ).

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