Hydro­gen bonds and C—H...O interactions in 2-(2-methyl­benzyl)­malonic acid at 150 K

The title compound, C₁₁H₁₂O₄, crystallized in the centrosymmetric space group Pbca with one mol­ecule as the asymmetric unit. The two hydrogen bonds have O_D...O_A distances of 2.667 (2) and 2.628 (2) Å, and O—H...O angles of 179 (2) and 177 (2)°. Each hydrogen bond forms an R(8) cyclic dimer about a center of symmetry. The leading intermolecular C—­H...O interaction has an H...O distance of 2.66 Å and a C—H...O angle of 160°. Taken together with the hydrogen bonds, it results in a three-dimensional network of inter­actions. The structure is compared with that of a close analog, benzyl­malonic acid.

S1. Comment

This report is one of a series on hydrogen bonding and C—H···O interactions in carboxylic acids. The title acid, (I), crystallized in the centrosymmetric space group Pbca with one molecule as the asymmetric unit. The refined molecule and the labelling scheme are given in Fig. 1. In the carboxyl groups, the C—O distances are somewhat less than usually observed, and the C═O distances are somewhat greater. The carboxyl O atoms are nonetheless ordered, as shown by the orientations of their substantially largest principal displacement components almost normal to the planes of their carboxyl groups (see, e.g. Fitzgerald & Gerkin, 1993). Moreover, although the refined O3-H1O3 distance, 1.23 (2) Å, is larger then usual and the isotropic displacement parameter of H1O3 is large, the interpretation of H1O3 as an ordered H atom is supported by the fact that H1O3 and H1O1 appeared as the top two peaks in the Fourier difference map after all other atoms were refined, and by the absence of any suitable residual electron-density peak near O4. Such a location of H1O3 is, of course, consistent with a flatter-than-usual potential function between the O atoms in the dimer. Thus, this is a case in which a neutron-diffraction determination would be of particular interest. Two hydrogen bonds and one leading intermolecular C—H···O interaction (Taylor & Kennard, 1982; Steiner & Desiraju, 1998) are present in this structure; five additional intermolecular C—H···O interactions of somewhat lesser significance are also present. The geometric parameters of all these are given in Table 2. The results of basic first- and second-level graph-set analysis (Bernstein et al., 1995) involving the three leading interactions, labelled a-c for this purpose in the order of their appearance in Table 2, are given in Table 3. Each hydrogen bond forms an R₂²(8) cyclic dimer about a center of symmetry. The chains given in Table 3 propagate along [100], [010], [010] and [001] in the order of their appearance. Thus a three-dimensional network of interactions is formed by the three leading interactions. A stereodiagram, Fig. 2, includes examples of each of these interactions. \sch

The phenyl ring in (I) is closely planar, the maximum deviation of a C atom from the best-fit plane describing them being 0.005 (2) Å, while the mean deviation is 0.003 (2) Å. The molecular configuration can be characterized in good part by the dihedral angles between the following planes: (1) the phenyl-ring plane; (2) the plane defined by C1, C2 and C3; (3) the carboxyl plane C1, O1 and O2; and (4) the carboxyl plane C3, O3 and O4. The values are as follows: (1) to (2), 60.4 (2); (1) to (3), 84.9 (2); (1) to (4), 64.9 (2); (2) to (3), 89.6 (2); (2) to (4), 4.6 (2); and (3) to (4), 88.2 (2)°. Fig. 2 makes some of these relations apparent, as well as illustrating the alternating layers, along the c axis, of hydrocarbon and carboxyl portions of molecules. For structural comparisons, benzylmalonic acid at room temperature [hereafter, (II)] (Lepore et al., 1975) appears particularly well suited. With respect to the dihedral angles just characterized for (I), the corresponding values for (II) are, respectively, 57.1 (4), 77.5 (5), 53.6 (4), 83.9 (5), 3.5 (5) and 83.7 (6)°. These values support the conclusion that (I) and (II) have very similar molecular conformations. Despite their similar molecular conformations, (I) and (II) pack quite differently, as demonstrated by their (conventional) hydrogen bonding. Whereas for (I) the first- and second-level graph-set descriptors are R₂²(8), R₂²(8) and C₂²(12), for (II) they are C(6), R₂²(12), and C₂²(8).

Selected bond distances and angles of (I) are given in Table 1. A l l distances and angles fall within normal limits. In (I) the closest intermolecular approaches, excluding pairs of atoms in hydrogen-bonded carboxyl groups or in the tabulated C—H···O interactions, are between O1 and O3^vii (vii = x − 1/2, 1/2 − y, −z) and fall short of the corresponding Bondi (1964) van der Waals radius sum by 0.10 Å.

S2. Experimental

(I) was obtained as a finely-crystalline, white powder from a sample in Dr M. S. Newman's chemical collection. Slow evaporation of a solution of this material in ether produced a suitable experimental sample. A synthesis is described by Harvey et al. (1982)

Computing details

Data collection: COLLECT (Nonius, 1999); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN; program(s) used to solve structure: SHELXS86 (Sheldrick, 1990); program(s) used to refine structure: TEXSAN (Molecular Structure Corporation, 1995); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: TEXSAN and PLATON (Spek, 1990).

Figures

	Fig. 1. Labeling scheme and displacement ellipsoids at the 50% probability level.
	Fig. 2. Packing stereodiagram of (I), with origin at the rear lower right. The finer interatomic lines depict interactions a-c (Tables 2 and 3).

(I)

Crystal data

C11H12O4	F(000) = 880
Mr = 208.21	Dx = 1.315 Mg m^−3
Orthorhombic, Pbca	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2ab	Cell parameters from 38725 reflections
a = 11.3705 (2) Å	θ = 1.1–27.5°
b = 9.7132 (2) Å	µ = 0.10 mm^−1
c = 19.0382 (3) Å	T = 150 K
V = 2102.65 (11) Å^3	Cut column, colorless
Z = 8	0.23 × 0.12 × 0.12 mm

Data collection

Nonius KappaCCD diffractometer	1777 reflections with I > 2.00σI
Radiation source: X-ray tube	Rint = 0.056
Graphite monochromator	θmax = 27.5°
ω scans with κ offsets	h = −14→14
38725 measured reflections	k = −12→12
2408 independent reflections	l = −24→24

Refinement

Refinement on F^2	H atoms treated by a mixture of independent and constrained refinement
Least-squares matrix: full	Weighting scheme based on measured s.u.'s w = 1/[σ^2cs + (0.018I)^2]
R[F^2 > 2σ(F^2)] = 0.048	(Δ/σ)max = 0.0003
wR(F^2) = 0.085	Δρmax = 0.38 e Å^−3
S = 1.97	Δρmin = −0.33 e Å^−3
2408 reflections	Extinction correction: Zachariasen (1963, 1968)
145 parameters	Extinction coefficient: 5.5 (10) × 10^-7

Special details

Experimental. The Laue group assignment, the systematic absences and the centrosymmetry indicated by the intensity statistics led uniquely to assignment of the space group as Pbca (No. 61); since refinement proceeded well, it was adopted. Fourier difference methods were used to locate initial H atom positions, and the H atoms were refined. Refined C—H distances ranged from 0.94 (1) to 1.00 (2) Å, with mean value 0.98 (2) Å; their U_iso values ranged from 0.8 to 1.4 times the U_eq values of the attached C atoms. The H atoms, excepting the carboxyl H atoms, were then made canonical, with C—H = 0.98 Å and U_iso = 1.2 × U_eq of the attached C atom. In the later stages of refinement the extinction coefficient was predicted to be positive, and was included in the model. The maximum peak in the final difference map occurs ~0.6 Å from C2, the maximum negative peak ~0.8 Å from C3.

Geometry. Table of Least-Squares Planes ——————————

————– Plane number 1 —————

Atoms Defining Plane Distance e.s.d. C5 (1) 0.0034 0.0012 C6 (1) 0.0008 0.0012 C7 (1) −0.0047 0.0013 C8 (1) 0.0037 0.0014 C9 (1) 0.0018 0.0014 C10 (1) −0.0047 0.0012

Additional Atoms Distance C4 (1) 0.0393 C11 (1) 0.0123

Mean deviation from plane is 0.0032 angstroms Chi-squared: 41.7

————– Plane number 2 —————

Atoms Defining Plane Distance e.s.d. C1 (1) 0.0000 C2 (1) 0.0000 C3 (1) 0.0000

Mean deviation from plane is 0.0000 angstroms Chi-squared: 0.0

Dihedral angles between least-squares planes plane plane angle 2 1 119.63

————– Plane number 3 —————

Atoms Defining Plane Distance e.s.d. O1 (1) 0.0000 O2 (1) 0.0000 C1 (1) 0.0000

Mean deviation from plane is 0.0000 angstroms Chi-squared: 0.0

Dihedral angles between least-squares planes plane plane angle 3 1 95.07 3 2 90.37

————– Plane number 4 —————

Atoms Defining Plane Distance e.s.d. O3 (1) 0.0000 O4 (1) 0.0000 C3 (1) 0.0000

Mean deviation from plane is 0.0000 angstroms Chi-squared: 0.0

Dihedral angles between least-squares planes plane plane angle 4 1 115.15 4 2 4.59 4 3 91.83

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.10151 (8)	0.13475 (9)	−0.01621 (5)	0.0350 (3)
O2	0.09763 (8)	−0.02815 (9)	0.06642 (4)	0.0331 (3)
O3	0.45678 (8)	0.13080 (10)	0.05506 (5)	0.0375 (3)
O4	0.34949 (7)	−0.02228 (9)	−0.00410 (4)	0.0341 (3)
C1	0.14186 (10)	0.07518 (13)	0.03926 (6)	0.0226 (4)
C2	0.25097 (10)	0.14146 (11)	0.06960 (6)	0.0218 (3)
C3	0.35883 (10)	0.07731 (13)	0.03737 (6)	0.0228 (4)
C4	0.25717 (10)	0.13254 (12)	0.14984 (6)	0.0258 (4)
C5	0.16591 (11)	0.21517 (12)	0.18934 (6)	0.0259 (4)
C6	0.16597 (12)	0.20993 (13)	0.26317 (6)	0.0311 (4)
C7	0.08327 (13)	0.28842 (14)	0.29952 (7)	0.0405 (5)
C8	0.00306 (13)	0.37094 (14)	0.26536 (8)	0.0443 (5)
C9	0.00277 (12)	0.37570 (13)	0.19318 (8)	0.0399 (4)
C10	0.08338 (11)	0.29773 (13)	0.15572 (7)	0.0305 (4)
C11	0.25317 (12)	0.12289 (14)	0.30206 (7)	0.0413 (4)
H1O1	0.0324 (18)	0.0962 (18)	−0.0339 (9)	0.098 (7)*
H1O3	0.549 (2)	0.083 (2)	0.0308 (11)	0.135 (8)*
H2	0.2500	0.2391	0.0566	0.026*
H4A	0.3350	0.1650	0.1645	0.031*
H4B	0.2479	0.0357	0.1631	0.031*
H7	0.0822	0.2848	0.3510	0.049*
H8	−0.0534	0.4259	0.2923	0.053*
H9	−0.0541	0.4339	0.1684	0.048*
H10	0.0822	0.3009	0.1043	0.037*
H11A	0.2389	0.1306	0.3527	0.050*
H11B	0.2446	0.0266	0.2876	0.050*
H11C	0.3330	0.1546	0.2914	0.050*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0307 (6)	0.0393 (6)	0.0350 (6)	−0.0036 (5)	−0.0107 (5)	0.0092 (5)
O2	0.0320 (6)	0.0353 (6)	0.0321 (5)	−0.0100 (5)	−0.0017 (4)	0.0055 (4)
O3	0.0187 (5)	0.0502 (6)	0.0436 (6)	−0.0059 (5)	0.0046 (4)	−0.0136 (5)
O4	0.0271 (5)	0.0374 (6)	0.0379 (6)	0.0000 (4)	0.0050 (4)	−0.0145 (5)
C1	0.0204 (7)	0.0249 (7)	0.0225 (7)	0.0033 (6)	0.0040 (6)	−0.0019 (6)
C2	0.0192 (7)	0.0208 (7)	0.0253 (7)	0.0007 (6)	0.0023 (6)	−0.0008 (5)
C3	0.0213 (7)	0.0256 (7)	0.0215 (7)	−0.0017 (6)	0.0004 (6)	0.0025 (6)
C4	0.0214 (7)	0.0300 (8)	0.0260 (7)	−0.0016 (6)	−0.0003 (6)	−0.0013 (6)
C5	0.0243 (7)	0.0244 (7)	0.0290 (8)	−0.0064 (6)	0.0069 (6)	−0.0035 (6)
C6	0.0341 (8)	0.0289 (8)	0.0303 (8)	−0.0103 (7)	0.0062 (7)	−0.0030 (6)
C7	0.0505 (10)	0.0386 (9)	0.0325 (8)	−0.0092 (8)	0.0184 (7)	−0.0069 (7)
C8	0.0464 (10)	0.0354 (9)	0.0512 (11)	0.0009 (8)	0.0255 (8)	−0.0075 (7)
C9	0.0379 (9)	0.0314 (8)	0.0504 (9)	0.0059 (7)	0.0164 (7)	0.0006 (7)
C10	0.0308 (8)	0.0294 (8)	0.0311 (8)	0.0003 (6)	0.0093 (6)	0.0004 (6)
C11	0.0422 (9)	0.0530 (10)	0.0288 (7)	−0.0090 (8)	0.0028 (7)	0.0013 (6)

Geometric parameters (Å, º)

O1—C1	1.2886 (15)	C5—C10	1.3904 (17)
O1—H1O1	0.93 (2)	C6—C7	1.3944 (19)
O2—C1	1.2360 (14)	C6—C11	1.4987 (19)
O3—C3	1.2742 (14)	C7—C8	1.377 (2)
O3—H1O3	1.23 (2)	C7—H7	0.98
O4—C3	1.2532 (14)	C8—C9	1.375 (2)
C1—C2	1.5124 (16)	C8—H8	0.98
C2—C3	1.5062 (16)	C9—C10	1.3865 (18)
C2—C4	1.5318 (15)	C9—H9	0.98
C2—H2	0.98	C10—H10	0.98
C4—C5	1.5120 (16)	C11—H11C	0.98
C4—H4B	0.98	C11—H11A	0.98
C4—H4A	0.98	C11—H11B	0.98
C5—C6	1.4065 (16)
C1—O1—H1O1	114.5 (11)	C6—C5—C10	118.8 (2)
C3—O3—H1O3	119.3 (9)	C5—C6—C7	118.4 (2)
O1—C1—O2	124.2 (2)	C5—C6—C11	121.0 (2)
O1—C1—C2	114.5 (2)	C7—C6—C11	120.6 (2)
O2—C1—C2	121.3 (2)	C6—C7—C8	122.0 (2)
C1—C2—C3	109.6 (2)	C6—C7—H7	119.0
C1—C2—C4	113.2 (2)	C8—C7—H7	119.0
C1—C2—H2	107.9	C7—C8—C9	119.5 (2)
C3—C2—C4	110.2 (2)	C7—C8—H8	120.2
C3—C2—H2	107.9	C9—C8—H8	120.2
C4—C2—H2	107.9	C8—C9—C10	119.6 (2)
O3—C3—O4	123.7 (2)	C8—C9—H9	120.2
O3—C3—C2	115.8 (2)	C10—C9—H9	120.2
O4—C3—C2	120.5 (2)	C5—C10—C9	121.6 (2)
C2—C4—C5	115.7 (2)	C5—C10—H10	119.2
C2—C4—H4B	107.9	C9—C10—H10	119.2
C2—C4—H4A	107.9	C6—C11—H11C	109.5
C5—C4—H4B	107.9	C6—C11—H11A	109.5
C5—C4—H4A	107.9	C6—C11—H11B	109.5
H4B—C4—H4A	109.5	H11C—C11—H11A	109.5
C4—C5—C6	118.5 (2)	H11C—C11—H11B	109.5
C4—C5—C10	122.7 (2)	H11A—C11—H11B	109.5
O1—C1—C2—C3	−90.18 (12)	C4—C5—C6—C7	178.71 (11)
O1—C1—C2—C4	146.29 (10)	C4—C5—C6—C11	−0.92 (17)
O2—C1—C2—C3	89.36 (13)	C4—C5—C10—C9	−178.08 (11)
O2—C1—C2—C4	−34.17 (15)	C5—C6—C7—C8	−0.56 (19)
O3—C3—C2—C1	175.38 (10)	C5—C10—C9—C8	−0.6 (2)
O3—C3—C2—C4	−59.32 (13)	C6—C5—C10—C9	0.82 (18)
O4—C3—C2—C1	−4.56 (15)	C6—C7—C8—C9	0.8 (2)
O4—C3—C2—C4	120.74 (11)	C7—C6—C5—C10	−0.24 (17)
C1—C2—C4—C5	−67.37 (12)	C7—C8—C9—C10	−0.2 (2)
C2—C4—C5—C6	179.21 (10)	C8—C7—C6—C11	179.07 (12)
C2—C4—C5—C10	−1.89 (16)	C10—C5—C6—C11	−179.86 (12)
C3—C2—C4—C5	169.40 (10)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1O1···O2^i	0.93 (2)	1.73 (2)	2.667 (2)	179 (2)
O3—H1O3···O4^ii	1.23 (2)	1.40 (2)	2.628 (2)	177 (2)
C7—H7···O1^iii	0.98	2.66	3.593 (2)	160
C7—H7···O3^iv	0.98	2.73	3.475 (2)	133
C8—H8···O2^v	0.98	2.77	3.540 (2)	136
C10—H10···O4^vi	0.98	2.80	3.591 (2)	139
C2—H2···O4^vi	0.98	2.83	3.734 (2)	154
C2—H2···O2^vi	0.98	2.85	3.642 (2)	138

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