Phenyl- and mesitylglyoxylic acids: catemeric hydrogen bonding in two α-keto acids

α-Oxo­benzene­acetic (phenyl­glyoxy­lic) acid, C₈H₆O₃, adopts a transoid di­carbonyl conformation in the solid state, with the carboxyl group rotated 44.4 (1)° from the nearly planar benzoyl moiety. The heterochiral acid-to-ketone catemers [O...O = 2.686 (3) and H...O = 1.78 (4) Å] have a second, longer, intermolecular O—H...O contact to a carboxyl sp³ O atom [O...O = 3.274 (2) and H...O = 2.72 (4) Å], with each flat ribbon-like chain lying in the bc plane and extending in the c direction. In α-oxo-2,4,6-tri­methyl­benzene­acetic (mesityl­glyoxy­lic) acid, C₁₁H₁₂O₃, the ketone is rotated 49.1 (7)° from planarity with the aryl ring and the carboxyl group is rotated a further 31.2 (7)° from the ketone plane. The solid consists of chiral conformers of a single handedness, aggregating in hydrogen-bonding chains whose units are related by a 3₁ screw axis, producing hydrogen-bonding helices that extend in the c direction. The hydrogen bonding is of the acid-to-acid type [O...O = 2.709 (6) and H...O = 1.87 (5) Å] and does not formally involve the ketone; however, the ketone O atom in the acceptor mol­ecule has a close polar contact with the same donor carboxyl group [O...O = 3.005 (6) and H...O = 2.50 (5) Å]. This secondary hydrogen bond is probably a major factor in stabilizing the observed cisoid di­carbonyl conformation. Several intermolecular C—H...O close contacts were found for the latter compound.

Computing details

For both compounds, data collection: XSCANS (Siemens, 1996); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXTL (Sheldrick, 1997); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

(I) α-Oxobenzeneacetic acid

Crystal data

C8H6O3	Dx = 1.381 Mg m^−3
Mr = 150.13	Melting point: 342 K
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 7.462 (2) Å	Cell parameters from 15 reflections
b = 16.513 (5) Å	θ = 3.2–12.3°
c = 6.483 (3) Å	µ = 0.11 mm^−1
β = 115.32 (2)°	T = 293 K
V = 722.1 (4) Å^3	Parallelepiped, colorless
Z = 4	0.64 × 0.50 × 0.30 mm
F(000) = 312

Data collection

Siemens P4 diffractometer	Rint = 0.022
Radiation source: normal-focus sealed tube	θmax = 25.0°, θmin = 2.5°
Graphite monochromator	h = −8→8
2θ–θ scans	k = −1→19
1562 measured reflections	l = −1→7
1271 independent reflections	3 standard reflections every 97 reflections
740 reflections with I > 2σ(I)	intensity decay: variation < 1.8%

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.059	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.153	H atoms treated by a mixture of independent and constrained refinement
S = 1.05	w = 1/[σ^2(Fo^2) + (0.0743P)^2] where P = (Fo^2 + 2Fc^2)/3
1271 reflections	(Δ/σ)max < 0.001
105 parameters	Δρmax = 0.20 e Å^−3
0 restraints	Δρmin = −0.19 e Å^−3

Special details

Experimental. Crystal mounted in glass capillary and coated with grease

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 (Ų)

	x	y	z	Uiso*/Ueq
O1	0.1528 (4)	0.62379 (13)	0.4709 (4)	0.0711 (7)
O2	0.3784 (4)	0.68636 (14)	0.1497 (4)	0.0777 (8)
O3	0.0991 (3)	0.73600 (13)	0.1469 (4)	0.0667 (7)
H3	0.125 (6)	0.780 (3)	0.075 (7)	0.123 (16)*
C1	0.2363 (4)	0.52537 (16)	0.2631 (5)	0.0510 (8)
C2	0.2801 (5)	0.50725 (19)	0.0795 (6)	0.0617 (9)
C3	0.3127 (5)	0.4272 (2)	0.0415 (7)	0.0761 (11)
C4	0.3020 (5)	0.3672 (2)	0.1792 (8)	0.0807 (12)
C5	0.2541 (5)	0.3844 (2)	0.3572 (7)	0.0808 (12)
C6	0.2219 (5)	0.46344 (18)	0.3989 (6)	0.0645 (9)
C7	0.2028 (4)	0.60937 (17)	0.3189 (5)	0.0523 (8)
C8	0.2376 (5)	0.68093 (17)	0.1917 (5)	0.0555 (8)
H2	0.2872	0.5481	−0.0155	0.085 (5)*
H3A	0.3424	0.4143	−0.0801	0.085 (5)*
H4	0.3274	0.3140	0.1530	0.085 (5)*
H5	0.2436	0.3430	0.4485	0.085 (5)*
H6	0.1901	0.4754	0.5195	0.085 (5)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.1039 (18)	0.0484 (13)	0.0811 (16)	−0.0081 (11)	0.0588 (15)	−0.0032 (12)
O2	0.0759 (16)	0.0660 (15)	0.108 (2)	0.0024 (12)	0.0554 (15)	0.0166 (13)
O3	0.0732 (15)	0.0471 (12)	0.0856 (18)	0.0051 (11)	0.0396 (13)	0.0091 (12)
C1	0.0442 (17)	0.0442 (16)	0.058 (2)	−0.0009 (13)	0.0156 (15)	0.0034 (15)
C2	0.058 (2)	0.059 (2)	0.069 (2)	−0.0046 (15)	0.0283 (18)	−0.0027 (17)
C3	0.067 (2)	0.069 (2)	0.088 (3)	0.0021 (19)	0.029 (2)	−0.023 (2)
C4	0.064 (2)	0.044 (2)	0.119 (4)	0.0031 (16)	0.025 (2)	−0.010 (2)
C5	0.083 (3)	0.0471 (19)	0.103 (3)	−0.0015 (18)	0.031 (2)	0.014 (2)
C6	0.067 (2)	0.0499 (18)	0.074 (2)	−0.0034 (15)	0.0280 (19)	0.0026 (17)
C7	0.0517 (18)	0.0452 (17)	0.061 (2)	−0.0049 (13)	0.0250 (16)	0.0012 (16)
C8	0.0580 (19)	0.0433 (16)	0.065 (2)	−0.0037 (15)	0.0262 (17)	−0.0020 (15)

Geometric parameters (Å, º)

O1—C7	1.217 (3)	C2—C3	1.386 (4)
O2—C8	1.196 (3)	C3—C4	1.358 (5)
O3—C8	1.312 (4)	C4—C5	1.376 (5)
C1—C6	1.383 (4)	C5—C6	1.374 (5)
C1—C2	1.395 (4)	C7—C8	1.525 (4)
C1—C7	1.481 (4)
C6—C1—C2	119.7 (3)	C5—C6—C1	120.6 (3)
C6—C1—C7	118.0 (3)	O1—C7—C1	121.5 (3)
C2—C1—C7	122.3 (3)	O1—C7—C8	117.9 (3)
C3—C2—C1	118.7 (3)	C1—C7—C8	120.6 (3)
C4—C3—C2	121.0 (4)	O2—C8—O3	125.7 (3)
C3—C4—C5	120.7 (3)	O2—C8—C7	123.4 (3)
C6—C5—C4	119.4 (3)	O3—C8—C7	110.9 (3)
C6—C1—C2—C3	−1.5 (5)	C6—C1—C7—O1	−4.2 (4)
C7—C1—C2—C3	178.9 (3)	C2—C1—C7—O1	175.4 (3)
C1—C2—C3—C4	0.2 (5)	C6—C1—C7—C8	173.6 (3)
C2—C3—C4—C5	1.4 (5)	C2—C1—C7—C8	−6.8 (4)
C3—C4—C5—C6	−1.7 (5)	O1—C7—C8—O2	134.3 (3)
C4—C5—C6—C1	0.3 (5)	C1—C7—C8—O2	−43.6 (4)
C2—C1—C6—C5	1.3 (5)	O1—C7—C8—O3	−42.5 (4)
C7—C1—C6—C5	−179.1 (3)	C1—C7—C8—O3	139.6 (3)

(II) α-oxo-2,4,6-trimethylbenzeneacetic acid

Crystal data

C11H12O3	Dx = 1.257 Mg m^−3
Mr = 192.21	Melting point: 392 K
Trigonal, P31	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 31	Cell parameters from 17 reflections
a = 9.121 (1) Å	θ = 5.6–12.0°
c = 10.576 (1) Å	µ = 0.09 mm^−1
V = 761.97 (14) Å^3	T = 248 K
Z = 3	Block, colorless
F(000) = 306	0.30 × 0.28 × 0.26 mm

Data collection

Siemens P4 diffractometer	574 reflections with I > 2σ(I)
Radiation source: normal-focus sealed tube	Rint = 0.046
Graphite monochromator	θmax = 25.0°, θmin = 2.6°
2θ–θ scans	h = −10→10
Absorption correction: numerical (SHELXTL; Sheldrick, 1997)	k = 0→10
Tmin = 0.967, Tmax = 0.977	l = 0→12
2050 measured reflections	3 standard reflections every 97 reflections
1772 independent reflections	intensity decay: variation < 3.3%

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.049	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.127	H atoms treated by a mixture of independent and constrained refinement
S = 1.02	w = 1/[σ^2(Fo^2) + (0.0648P)^2] where P = (Fo^2 + 2Fc^2)/3
886 reflections	(Δ/σ)max < 0.001
141 parameters	Δρmax = 0.13 e Å^−3
1 restraint	Δρmin = −0.18 e Å^−3

Special details

Experimental. Crystal mounted on glass fiber using epoxy cement

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 with 886 Friedel pairs merged. 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 (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
O1	0.6580 (6)	0.8177 (6)	0.2937 (4)	0.0803 (14)
O2	0.3786 (5)	0.7123 (5)	0.1425 (4)	0.0607 (10)
O3	0.5133 (5)	0.6231 (5)	0.0138 (3)	0.0538 (10)
H3	0.434 (6)	0.615 (5)	−0.039 (5)	0.031 (13)*
C1	0.6922 (7)	0.5872 (7)	0.2251 (5)	0.0493 (15)
C2	0.8699 (7)	0.6594 (7)	0.2300 (5)	0.0529 (14)
C3	0.9367 (8)	0.5533 (9)	0.2347 (5)	0.0647 (17)
C4	0.8351 (9)	0.3801 (9)	0.2392 (5)	0.0595 (16)
C5	0.6630 (8)	0.3119 (8)	0.2361 (5)	0.0591 (17)
C6	0.5883 (7)	0.4115 (7)	0.2286 (5)	0.0502 (15)
C7	0.6204 (7)	0.6998 (7)	0.2226 (5)	0.0527 (14)
C8	0.4881 (7)	0.6756 (7)	0.1218 (5)	0.0504 (13)
C9	0.9885 (8)	0.8482 (8)	0.2232 (6)	0.075 (2)
C10	0.9125 (11)	0.2667 (11)	0.2484 (7)	0.089 (2)
C11	0.3965 (8)	0.3292 (8)	0.2295 (5)	0.0669 (18)
H3A	1.0549	0.6005	0.2347	0.065 (19)*
H5	0.5934	0.1936	0.2392	0.031 (13)*
H9A	1.0995	0.8707	0.1961	0.091 (19)*	0.77 (8)
H9B	0.9972	0.8978	0.3059	0.091 (19)*	0.77 (8)
H9C	0.9451	0.8974	0.1630	0.091 (19)*	0.77 (8)
H9D	0.9283	0.9065	0.2472	0.091 (19)*	0.23 (8)
H9E	1.0307	0.8795	0.1375	0.091 (19)*	0.23 (8)
H9F	1.0828	0.8799	0.2804	0.091 (19)*	0.23 (8)
H10A	0.8229	0.1493	0.2523	0.092 (19)*	0.75 (8)
H10B	0.9815	0.2949	0.3240	0.092 (19)*	0.75 (8)
H10C	0.9824	0.2835	0.1746	0.092 (19)*	0.75 (8)
H10D	1.0349	0.3358	0.2483	0.092 (19)*	0.25 (8)
H10E	0.8764	0.1902	0.1766	0.092 (19)*	0.25 (8)
H10F	0.8755	0.2016	0.3260	0.092 (19)*	0.25 (8)
H11A	0.3474	0.2167	0.2658	0.063 (10)*
H11B	0.3559	0.3211	0.1436	0.063 (10)*
H11C	0.3638	0.3972	0.2797	0.063 (10)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.098 (3)	0.087 (3)	0.076 (3)	0.061 (3)	−0.029 (2)	−0.038 (3)
O2	0.061 (2)	0.084 (3)	0.049 (2)	0.045 (2)	−0.002 (2)	−0.007 (2)
O3	0.053 (2)	0.072 (3)	0.0382 (18)	0.033 (2)	−0.0096 (18)	−0.0090 (18)
C1	0.052 (4)	0.055 (4)	0.036 (3)	0.023 (3)	−0.002 (3)	−0.003 (2)
C2	0.052 (4)	0.060 (4)	0.044 (3)	0.026 (3)	−0.009 (3)	−0.001 (3)
C3	0.055 (4)	0.090 (5)	0.053 (4)	0.039 (4)	0.002 (3)	0.011 (3)
C4	0.076 (5)	0.071 (5)	0.044 (3)	0.046 (4)	0.004 (3)	0.008 (3)
C5	0.077 (5)	0.055 (4)	0.034 (3)	0.025 (4)	0.001 (3)	0.006 (3)
C6	0.048 (3)	0.057 (4)	0.032 (3)	0.016 (3)	0.001 (2)	0.004 (3)
C7	0.064 (4)	0.057 (4)	0.040 (3)	0.032 (3)	0.001 (3)	−0.007 (3)
C8	0.047 (3)	0.055 (3)	0.045 (3)	0.023 (3)	0.001 (3)	−0.001 (3)
C9	0.059 (4)	0.069 (5)	0.085 (5)	0.024 (4)	−0.014 (3)	0.001 (3)
C10	0.119 (6)	0.118 (6)	0.067 (5)	0.086 (6)	0.019 (4)	0.022 (4)
C11	0.062 (4)	0.065 (4)	0.049 (4)	0.014 (3)	0.005 (3)	0.014 (3)

Geometric parameters (Å, º)

O1—C7	1.213 (6)	C2—C9	1.509 (9)
O2—C8	1.221 (6)	C3—C4	1.375 (9)
O3—C8	1.303 (6)	C4—C5	1.369 (9)
C1—C6	1.396 (7)	C4—C10	1.519 (9)
C1—C2	1.412 (8)	C5—C6	1.384 (9)
C1—C7	1.469 (8)	C6—C11	1.520 (9)
C2—C3	1.380 (8)	C7—C8	1.541 (8)
C6—C1—C2	119.8 (5)	C4—C5—C6	122.1 (6)
C6—C1—C7	121.2 (5)	C5—C6—C1	118.7 (5)
C2—C1—C7	118.9 (5)	C5—C6—C11	119.9 (5)
C3—C2—C1	118.7 (6)	C1—C6—C11	121.4 (6)
C3—C2—C9	119.1 (6)	O1—C7—C1	125.5 (5)
C1—C2—C9	122.1 (5)	O1—C7—C8	114.3 (5)
C4—C3—C2	121.8 (6)	C1—C7—C8	120.2 (5)
C5—C4—C3	118.8 (6)	O2—C8—O3	125.2 (5)
C5—C4—C10	120.6 (7)	O2—C8—C7	121.7 (5)
C3—C4—C10	120.5 (6)	O3—C8—C7	113.0 (5)
C6—C1—C2—C3	1.8 (6)	C2—C1—C6—C5	−0.4 (6)
C7—C1—C2—C3	178.9 (5)	C7—C1—C6—C5	−177.4 (5)
C6—C1—C2—C9	178.4 (5)	C2—C1—C6—C11	177.2 (5)
C7—C1—C2—C9	−4.6 (7)	C7—C1—C6—C11	0.2 (7)
C1—C2—C3—C4	−2.4 (7)	C6—C1—C7—O1	128.0 (6)
C9—C2—C3—C4	−179.1 (5)	C2—C1—C7—O1	−49.0 (8)
C2—C3—C4—C5	1.5 (8)	C6—C1—C7—C8	−53.4 (7)
C2—C3—C4—C10	−178.1 (5)	C2—C1—C7—C8	129.6 (5)
C3—C4—C5—C6	0.0 (8)	O1—C7—C8—O2	−31.4 (8)
C10—C4—C5—C6	179.6 (5)	C1—C7—C8—O2	149.8 (5)
C4—C5—C6—C1	−0.5 (7)	O1—C7—C8—O3	144.8 (5)
C4—C5—C6—C11	−178.2 (5)	C1—C7—C8—O3	−34.0 (7)