trans-4-Acetylcyclo­hexane­carboxyl­ic acid and ()-trans-2-acetyl­cyclo­hexane­carboxyl­ic acid: hydrogen-bonding patterns in two isomeric keto acids

Both title compounds, C₉H₁₄O₃, display carboxyl-dimer hydrogen-bonding patterns. The 4-acetyl isomer adopts a chiral conformation with negligible disordering of the methyl and carboxyl groups and forms centrosymmetric dimers across the b and c edges of the chosen cell [O...O = 2.667 (3) Å and O—H...O = 175°]. Intermolecular C—H...O close contacts were found for both carbonyl groups. In the 2-acetyl isomer, there is no intramolecular interaction between the carboxyl and acetyl groups and the hydrogen bonding involves centrosymmetric carboxyl dimerization across the ab and ac faces of the chosen cell [O...O = 2.668 (2) Å and O—H...O = 173°]. The carboxyl group is negligibly disordered, but significant rotational disordering was found for the acetyl methyl group. An intermolecular C—H...O close contact was found involving the ketone group.

S1. Comment

Five hydrogen-bonding modes are known for the crystalline keto carboxylic acids that form the subject of our continuing study. Two of these have no ketone involvement, reflecting the common pairing and much rarer chain modes seen in simple acids (Leiserowitz, 1976). Acid-to-ketone chains (catemers) constitute a sizable minority of cases, while intramolecular hydrogen bonds and acid-to-ketone dimers are rarely observed. Hydrates with more complex hydrogen-bonding patterns also exist. We have previously provided examples of all of these, along with discussion of factors that appear to govern the choice of mode.

We report here the structure and hydrogen-bonding behavior of the title compounds, an ε-keto acid, trans-4-acetylcyclohexanecarboxylic acid, (I), and its γ-keto isomer, (±)-trans-2-acetylcyclohexanecarboxylic acid, (II). Both ε- and γ-keto acids are rich in hydrogen-bonding types, embracing not only dimers, but catemers of both the homo- and heterochiral types and internal hydrogen bonds, as well as hydrated patterns. Among those keto acids that adopt the catemeric hydrogen-bonding mode, we have identified the lack of conformational flexibility as one of the characteristics they have in common (Lalancette et al., 1999; Barcon et al., 1998, 2002). Compounds (I) and (II) were both of interest to us as part of a group of simple cyclohexane keto acids whose choice of hydrogen-bonding mode appears to correlate strongly with such conformational flexibility, as assessed by the number of fully rotatable bonds.

Fig. 1 shows the asymmetric unit of (I) with its atom numbering. Given the expected chair conformation, the only significant rotational options involve the equatorial substituent bonds. The acetyl group is turned roughly orthogonal to the general plane of the cyclohexane ring, so that the O1—C7—C4—C3 torsion angle is -27.0 (5)° (a perfect orthogonality angle would be 60°). The carboxyl carbonyl group is turned slightly toward the opposite face of the ring, so that the O2—C9—C1—C2 torsion angle is -15.2 (4)°. The intramolecular dihedral angle between the carboxyl and ketone planes is 81.1 (2)°.

Although not seen in catemeric hydrogen bonding, full or partial averaging of C—O bond lengths and C—C—O angles through disorder is often observed in dimerically hydrogen-bonded acids (Leiserowitz, 1976). However, no significant averaging is present in (I), where these C—O bond lengths are 1.222 (4)/1.300 (3) Å, with angles of 124.0 (3)/114.5 (3)°. Our own survey of 56 keto acid structures that are not acid dimers gives average values of 1.200 (10)/1.32 (2) Å and 124.5 (14)/112.7 (17)° for these lengths and angles, in accord with typical values of 1.21/1.31 Å and 123/112° cited for highly ordered dimeric carboxyls (Borthwick, 1980). No rotational disordering of the acetyl methyl group was observed.

Fig. 2 shows the cell packing in (I), which involves formation of centrosymmetric dimers across the b and c edges of the chosen cell [O···O = 2.667 (3) Å and O—H···O = 175°]. Within the 2.7 Å range we usually employ for non-bonded H···O packing interactions (Steiner, 1997), an intermolecular C—H···O close contact was found for the ketone (2.54 Å to atom H1 in a molecule screw-related in b), as well as for the acid (O3···H6B = 2.68 Å, in a molecule related through the center of symmetry at the origin). Using compiled data for a large number of C—H···O contacts, Steiner & Desiraju (1998) have found significant statistical directionality even as far out as 3.0 Å and conclude that these are legitimately viewed as `weak hydrogen bonds,' with a greater contribution to packing forces than simple van der Waals attractions.

Fig. 3 shows the asymmetric unit for (II) with its atom numbering. As in (I), only the equatorial substituent bonds offer significant rotational options. The acetyl group is turned so that the O1—C7—C2—C1 torsion angle is 13.8 (3)° and the carboxyl group is turned so that the O2—C9—C1—C2 torsion angle is 26.0 (3)°. The intramolecular dihedral angle between the carboxyl and ketone planes in (II) is 74.8 (2)°. A variety of vicinal and other carboxy ketones are known to close internally to form lactols (Chadwick & Dunitz, 1979; Thompson et al., 1985), including the aromatic analog of (II), 2-acetylbenzoic acid (Dobson & Gerkin, 1996; Valente et al., 1998). Unlike these, compound (II) has no intramolecular interaction between its two functional groups. The carboxyl C—O distances and C—C—O angles found for (II) [1.229 (3)/1.302 (3)° and 122.8 (2)/114.5 (2) Å], like those for (I), indicate a negligible degree of disordering. However, significant rotational disorder was found in the acetyl methyl group; refinement of partial H atoms found in electron-density difference maps provided a 78 (3):22 (3) population ratio for the two conformers involved, which differ by a rotation of 60°.

Fig. 4 shows the packing arrangement for (II) involving centrosymmetric dimers centered on the ab and ac faces of the chosen cell [O···O = 2.668 (2) Å and O—H···O = 173°]. For the ketone carbonyl group, a 2.66 Å intermolecular C—H···O close contact was found to atom H2A in a neighbor screw-related in b.

Among several factors tending to disfavor the kind of standard dimeric carboxyl hydrogen bonding seen in (I) and (II), we have identified low availability of alternative conformations as a major candidate. The flexibility associated with cyclohexane rings is a solution characteristic; in the crystal, the strong preference for chair conformations and equatorial substituents actually leaves systems like (I) and (II) with a diminished repertoire of conformational options. Nevertheless, in both (I) and (II), the fully rotatable bond by which the ketone function is attached allows sufficient flexibility for the system to find a centrosymmetric carboxyl-dimerization arrangement of favorably low energy. This contrasts with the case of several substituted cyclohexanone and cyclopentanone systems we have studied, where incorporation of the ketone into the ring removes that increment of flexibility, resulting in catemeric hydrogen-bonding arrangements (Lalancette et al., 1997; Thompson et al., 1998; Barcon et al., 1998, 2002; Zewge et al., 1998).

The solid-state (KBr) IR spectrum of (I) has separate C═O absorptions at 1712 and 1691 cm^-1 for the ketone and carboxyl groups, respectively, which coalesce to a single band at 1705 cm^-1 in CHCl₃ solution. Compound (II) in KBr has a single peak at 1695 cm^-1 for both C═O groups, which shifts to 1707 cm^-1 in CHCl₃. Both solution spectra display typical carboxyl-dilution shoulders around 1735 cm^-1.

S2. Experimental

Compound (I) was prepared by a Jones oxidation of the product from Rh-catalyzed hydrogenation of 4-acetylbenzoic acid; chilled crystallization separated (I) from the non-ketonic hydrogenolyzed material. Crystals of X-ray quality were produced from hexane/diethyl ether (m.p. 384 K). For (II), cyanide addition to 1-acetylcyclohexene, followed by ketone protection, base hydrolysis and deprotection, yielded material suitable for X-ray analysis after recrystallization from cyclohexane/diethyl ether (m.p. 409 K).

S3. Refinement

All H atoms in (I) and (II) were found in electron-density difference maps, but were placed in calculated positions (C—H = 0.96 Å for the methyl, 0.97 Å for the methylene, 0.98 Å for the methine and 0.82 Å for the carboxyl H atoms) and allowed to refine as riding models on their respective C and O parent atoms. Their displacement parameters were fixed at 120% of those of their respective C atoms and 150% of the respective O atoms. The methyl group of (II) exhibited significant disorder [population ratio = 78 (3):22 (3)].

Computing details

For both compounds, data collection: XSCANS (Siemens, 1996). Cell refinement: XSCANS) for (I); XSCANS for (II). Data reduction: XSCANS) for (I); XSCANS for (II). For both compounds, program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP in SHELXL97; software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The asymmetric unit of (I), with the atom-numbering scheme. Displacement ellipsoids are set at the 20% probability level.
	Fig. 2. A partial packing diagram for (I), with extracellular molecules to show the dimers centered on the b and c edges of the chosen cell. All C-bound H atoms have been omitted for clarity. Displacement ellipsoids are set at the 20% probability level.
	Fig. 3. The asymmetric unit of (II), with the atom-numbering scheme. Only the major disorder component [78 (3):22 (3)] of the methyl group is displayed. Displacement ellipsoids are set at the 20% probability level.
	Fig. 4. A partial packing diagram for (II), with extracellular molecules, illustrating the centrosymmetric carboxyl dimers across the ab and ac faces of the chosen cell. Displacement ellipsoids are set at the 20% probability level.

(I) trans-4-acetylcyclohexanecarboxylic acid

Crystal data

C9H14O3	F(000) = 368
Mr = 170.20	Dx = 1.235 Mg m^−3
Monoclinic, P21/c	Melting point: 384 K
Hall symbol: -P 2ybc	Mo Kα radiation, λ = 0.71073 Å
a = 9.845 (5) Å	Cell parameters from 13 reflections
b = 6.770 (5) Å	θ = 3.0–9.1°
c = 13.994 (8) Å	µ = 0.09 mm^−1
β = 101.12 (3)°	T = 296 K
V = 915.2 (10) Å^3	Parallelepiped, colourless
Z = 4	0.38 × 0.24 × 0.20 mm

Data collection

Siemens P4 diffractometer	Rint = 0.034
Radiation source: fine-focus sealed tube	θmax = 25.0°, θmin = 2.1°
Graphite monochromator	h = −11→1
2θ/θ scans	k = −8→1
2253 measured reflections	l = −16→16
1608 independent reflections	3 standard reflections every 97 reflections
996 reflections with I > 2σ(I)	intensity decay: variation <4.1%

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.059	H-atom parameters constrained
wR(F^2) = 0.166	w = 1/[σ^2(Fo^2) + (0.0538P)^2 + 0.6069P] where P = (Fo^2 + 2Fc^2)/3
S = 1.04	(Δ/σ)max < 0.001
1608 reflections	Δρmax = 0.19 e Å^−3
110 parameters	Δρmin = −0.17 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.012 (3)

Special details

Experimental. crystal mounted on glass fiber using cyanoacrylate 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. 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	0.5024 (3)	−0.1834 (5)	0.41144 (19)	0.1010 (10)
O2	0.0786 (2)	0.4929 (4)	0.11542 (15)	0.0745 (8)
O3	0.0852 (2)	0.2635 (3)	0.00508 (14)	0.0758 (8)
C1	0.2099 (3)	0.1991 (4)	0.16243 (19)	0.0507 (7)
C2	0.2771 (3)	0.3003 (5)	0.2560 (2)	0.0673 (10)
C3	0.3699 (3)	0.1590 (5)	0.3232 (2)	0.0707 (10)
C4	0.2921 (3)	−0.0210 (5)	0.34585 (19)	0.0534 (8)
C5	0.2224 (3)	−0.1219 (5)	0.2521 (2)	0.0677 (10)
C6	0.1300 (3)	0.0182 (5)	0.1842 (2)	0.0630 (9)
C7	0.3802 (3)	−0.1697 (5)	0.4100 (2)	0.0624 (9)
C8	0.3130 (4)	−0.2993 (6)	0.4727 (3)	0.0849 (12)
C9	0.1198 (3)	0.3324 (5)	0.0932 (2)	0.0522 (7)
H3	0.0350	0.3433	−0.0290	0.114*
H1	0.2843	0.1532	0.1304	0.061*
H2A	0.2059	0.3505	0.2888	0.081*
H2B	0.3315	0.4116	0.2411	0.081*
H3A	0.4460	0.1183	0.2927	0.085*
H3B	0.4087	0.2266	0.3834	0.085*
H4	0.2193	0.0231	0.3798	0.064*
H5A	0.2928	−0.1742	0.2192	0.081*
H5B	0.1675	−0.2319	0.2678	0.081*
H6A	0.0533	0.0591	0.2140	0.076*
H6B	0.0922	−0.0495	0.1239	0.076*
H8A	0.3807	−0.3869	0.5088	0.127*
H8B	0.2414	−0.3752	0.4327	0.127*
H8C	0.2734	−0.2197	0.5170	0.127*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0700 (16)	0.138 (3)	0.0979 (19)	0.0473 (17)	0.0241 (14)	0.0452 (18)
O2	0.0977 (18)	0.0654 (15)	0.0517 (13)	0.0160 (14)	−0.0078 (12)	−0.0028 (11)
O3	0.1002 (17)	0.0688 (15)	0.0486 (12)	0.0096 (13)	−0.0101 (11)	−0.0022 (11)
C1	0.0485 (16)	0.0553 (18)	0.0470 (15)	0.0006 (14)	0.0059 (13)	0.0030 (13)
C2	0.072 (2)	0.056 (2)	0.0617 (19)	−0.0068 (17)	−0.0161 (16)	0.0024 (16)
C3	0.068 (2)	0.066 (2)	0.065 (2)	−0.0037 (19)	−0.0184 (16)	0.0027 (18)
C4	0.0516 (17)	0.062 (2)	0.0459 (15)	0.0124 (15)	0.0072 (13)	0.0026 (14)
C5	0.076 (2)	0.053 (2)	0.065 (2)	−0.0029 (17)	−0.0095 (17)	0.0072 (16)
C6	0.0649 (19)	0.0547 (19)	0.0598 (18)	−0.0109 (17)	−0.0119 (15)	0.0065 (16)
C7	0.062 (2)	0.078 (2)	0.0467 (16)	0.0193 (18)	0.0071 (14)	0.0046 (16)
C8	0.085 (2)	0.095 (3)	0.072 (2)	0.006 (2)	0.0085 (19)	0.024 (2)
C9	0.0560 (18)	0.0570 (19)	0.0408 (15)	−0.0076 (16)	0.0024 (13)	0.0006 (14)

Geometric parameters (Å, º)

O1—C7	1.203 (4)	C1—H1	0.9800
O2—C9	1.222 (4)	C2—H2A	0.9700
O3—C9	1.300 (3)	C2—H2B	0.9700
C1—C9	1.486 (4)	C3—H3A	0.9700
C1—C2	1.513 (4)	C3—H3B	0.9700
C1—C6	1.518 (4)	C4—H4	0.9800
C2—C3	1.517 (4)	C5—H5A	0.9700
C3—C4	1.506 (4)	C5—H5B	0.9700
C4—C7	1.507 (4)	C6—H6A	0.9700
C4—C5	1.520 (4)	C6—H6B	0.9700
C5—C6	1.515 (4)	C8—H8A	0.9600
C7—C8	1.483 (5)	C8—H8B	0.9600
O3—H3	0.8200	C8—H8C	0.9600
C9—C1—C2	113.3 (3)	C4—C3—H3A	109.3
C9—C1—C6	110.7 (2)	C2—C3—H3A	109.3
C2—C1—C6	110.4 (2)	C4—C3—H3B	109.3
C1—C2—C3	111.2 (3)	C2—C3—H3B	109.3
C4—C3—C2	111.8 (3)	H3A—C3—H3B	107.9
C3—C4—C7	114.1 (3)	C3—C4—H4	107.8
C3—C4—C5	110.2 (2)	C7—C4—H4	107.8
C7—C4—C5	109.0 (3)	C5—C4—H4	107.8
C6—C5—C4	112.1 (3)	C6—C5—H5A	109.2
C5—C6—C1	111.0 (2)	C4—C5—H5A	109.2
O1—C7—C8	120.2 (3)	C6—C5—H5B	109.2
O1—C7—C4	121.3 (3)	C4—C5—H5B	109.2
C8—C7—C4	118.5 (3)	H5A—C5—H5B	107.9
O2—C9—O3	121.4 (3)	C5—C6—H6A	109.4
O2—C9—C1	124.0 (3)	C1—C6—H6A	109.4
O3—C9—C1	114.5 (3)	C5—C6—H6B	109.4
C9—O3—H3	109.5	C1—C6—H6B	109.4
C9—C1—H1	107.4	H6A—C6—H6B	108.0
C2—C1—H1	107.4	C7—C8—H8A	109.5
C6—C1—H1	107.4	C7—C8—H8B	109.5
C1—C2—H2A	109.4	H8A—C8—H8B	109.5
C3—C2—H2A	109.4	C7—C8—H8C	109.5
C1—C2—H2B	109.4	H8A—C8—H8C	109.5
C3—C2—H2B	109.4	H8B—C8—H8C	109.5
H2A—C2—H2B	108.0
C9—C1—C2—C3	−178.9 (3)	C2—C1—C6—C5	−55.7 (3)
C6—C1—C2—C3	56.3 (3)	C3—C4—C7—O1	−27.0 (5)
C1—C2—C3—C4	−56.8 (4)	C5—C4—C7—O1	96.7 (4)
C2—C3—C4—C7	178.3 (3)	C3—C4—C7—C8	152.5 (3)
C2—C3—C4—C5	55.2 (4)	C5—C4—C7—C8	−83.8 (4)
C3—C4—C5—C6	−54.9 (4)	C2—C1—C9—O2	−15.2 (4)
C7—C4—C5—C6	179.2 (3)	C6—C1—C9—O2	109.4 (3)
C4—C5—C6—C1	55.6 (4)	C2—C1—C9—O3	165.8 (3)
C9—C1—C6—C5	178.1 (3)	C6—C1—C9—O3	−69.6 (3)

(II) trans-2-acetylcyclohexanecarboxylic acid

Crystal data

C9H14O3	F(000) = 368
Mr = 170.20	Dx = 1.240 Mg m^−3
Monoclinic, P21/c	Melting point: 409 K
Hall symbol: -P 2ybc	Mo Kα radiation, λ = 0.71073 Å
a = 6.943 (2) Å	Cell parameters from 28 reflections
b = 10.489 (3) Å	θ = 2.5–10.1°
c = 12.778 (4) Å	µ = 0.09 mm^−1
β = 101.47 (2)°	T = 296 K
V = 912.0 (5) Å^3	Parallelepiped, colourless
Z = 4	0.36 × 0.32 × 0.14 mm

Data collection

Siemens P4 diffractometer	912 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.086
Graphite monochromator	θmax = 25.0°, θmin = 2.5°
2θ/θ scans	h = −8→8
Absorption correction: numerical (Sheldrick, 1997)	k = −12→12
Tmin = 0.97, Tmax = 0.99	l = −15→15
3465 measured reflections	3 standard reflections every 97 reflections
1599 independent reflections	intensity decay: variation <3%

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.052	H-atom parameters constrained
wR(F^2) = 0.104	w = 1/[σ^2(Fo^2) + (0.0187P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.99	(Δ/σ)max < 0.001
1599 reflections	Δρmax = 0.15 e Å^−3
112 parameters	Δρmin = −0.13 e Å^−3
0 restraints	Extinction correction: SHELXL97
Primary atom site location: structure-invariant direct methods	Extinction coefficient: none

Special details

Experimental. crystal mounted on glass fiber using epoxy resin

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	Occ. (<1)
O1	0.4841 (3)	1.04319 (18)	0.16824 (16)	0.0787 (7)
O2	0.4662 (3)	0.90097 (16)	0.39422 (13)	0.0542 (5)
O3	0.7196 (3)	1.02941 (17)	0.45112 (13)	0.0630 (6)
C1	0.7425 (3)	0.8925 (2)	0.30749 (17)	0.0388 (6)
C2	0.6104 (3)	0.8346 (2)	0.20943 (16)	0.0363 (6)
C3	0.7354 (4)	0.7803 (2)	0.13316 (19)	0.0499 (7)
C4	0.8864 (4)	0.6840 (3)	0.18820 (19)	0.0560 (8)
C5	1.0155 (4)	0.7418 (3)	0.2861 (2)	0.0615 (8)
C6	0.8939 (4)	0.7945 (2)	0.36330 (19)	0.0514 (7)
C7	0.4655 (4)	0.9301 (3)	0.15017 (19)	0.0468 (7)
C8	0.2996 (4)	0.8811 (3)	0.0659 (2)	0.0701 (9)
C9	0.6285 (4)	0.9426 (2)	0.38695 (17)	0.0389 (6)
H3	0.6551	1.0465	0.4966	0.095*
H1	0.8143	0.9638	0.2838	0.047*
H2A	0.5362	0.7643	0.2330	0.044*
H3A	0.6498	0.7395	0.0733	0.060*
H3B	0.8028	0.8497	0.1054	0.060*
H4A	0.8192	0.6099	0.2089	0.067*
H4B	0.9674	0.6563	0.1388	0.067*
H5A	1.0934	0.8100	0.2643	0.074*
H5B	1.1050	0.6774	0.3220	0.074*
H6A	0.9803	0.8347	0.4232	0.062*
H6B	0.8261	0.7250	0.3907	0.062*
H8A	0.1956	0.9429	0.0532	0.105*	0.78 (3)
H8B	0.2512	0.8027	0.0896	0.105*	0.78 (3)
H8C	0.3459	0.8663	0.0010	0.105*	0.78 (3)
H8D	0.3328	0.7983	0.0426	0.105*	0.22 (3)
H8E	0.2772	0.9386	0.0062	0.105*	0.22 (3)
H8F	0.1826	0.8750	0.0949	0.105*	0.22 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0997 (17)	0.0519 (12)	0.0773 (14)	0.0197 (13)	0.0003 (13)	−0.0048 (11)
O2	0.0496 (11)	0.0674 (12)	0.0505 (11)	−0.0157 (10)	0.0217 (9)	−0.0188 (9)
O3	0.0650 (13)	0.0742 (13)	0.0577 (11)	−0.0243 (11)	0.0311 (10)	−0.0343 (10)
C1	0.0459 (14)	0.0401 (14)	0.0314 (12)	−0.0083 (13)	0.0105 (11)	−0.0053 (11)
C2	0.0389 (14)	0.0394 (13)	0.0323 (12)	−0.0013 (11)	0.0115 (11)	−0.0040 (11)
C3	0.0527 (17)	0.0607 (17)	0.0366 (13)	0.0016 (15)	0.0094 (13)	−0.0108 (13)
C4	0.0604 (19)	0.0620 (18)	0.0476 (14)	0.0111 (15)	0.0154 (15)	−0.0085 (13)
C5	0.0489 (18)	0.081 (2)	0.0543 (16)	0.0175 (15)	0.0087 (15)	−0.0085 (15)
C6	0.0454 (17)	0.0700 (19)	0.0367 (13)	0.0047 (14)	0.0026 (13)	−0.0089 (13)
C7	0.0556 (18)	0.0507 (17)	0.0379 (14)	0.0062 (14)	0.0185 (14)	−0.0009 (12)
C8	0.064 (2)	0.086 (2)	0.0540 (17)	0.0047 (18)	−0.0030 (16)	0.0074 (16)
C9	0.0464 (16)	0.0396 (14)	0.0308 (12)	−0.0041 (13)	0.0081 (12)	−0.0036 (11)

Geometric parameters (Å, º)

O1—C7	1.211 (3)	C3—H3A	0.9700
O2—C9	1.229 (3)	C3—H3B	0.9700
O3—C9	1.302 (3)	C4—H4A	0.9700
C1—C9	1.501 (3)	C4—H4B	0.9700
C1—C2	1.524 (3)	C5—H5A	0.9700
C1—C6	1.540 (3)	C5—H5B	0.9700
C2—C7	1.512 (3)	C6—H6A	0.9700
C2—C3	1.537 (3)	C6—H6B	0.9700
C3—C4	1.523 (3)	C8—H8A	0.9600
C4—C5	1.513 (3)	C8—H8B	0.9600
C5—C6	1.524 (3)	C8—H8C	0.9600
C7—C8	1.503 (4)	C8—H8D	0.9602
O3—H3	0.8200	C8—H8E	0.9601
C1—H1	0.9800	C8—H8F	0.9601
C2—H2A	0.9800
C9—C1—C2	112.54 (19)	H4A—C4—H4B	108.1
C9—C1—C6	108.90 (18)	C4—C5—H5A	109.3
C2—C1—C6	110.99 (19)	C6—C5—H5A	109.3
C7—C2—C1	112.3 (2)	C4—C5—H5B	109.3
C7—C2—C3	109.33 (18)	C6—C5—H5B	109.3
C1—C2—C3	110.20 (19)	H5A—C5—H5B	108.0
C4—C3—C2	112.09 (19)	C5—C6—H6A	109.5
C5—C4—C3	110.9 (2)	C1—C6—H6A	109.5
C4—C5—C6	111.5 (2)	C5—C6—H6B	109.5
C5—C6—C1	110.9 (2)	C1—C6—H6B	109.5
O1—C7—C8	120.6 (3)	H6A—C6—H6B	108.0
O1—C7—C2	121.3 (3)	C7—C8—H8A	109.5
C8—C7—C2	118.1 (2)	C7—C8—H8B	109.5
O2—C9—O3	122.6 (2)	H8A—C8—H8B	109.5
O2—C9—C1	122.8 (2)	C7—C8—H8C	109.5
O3—C9—C1	114.5 (2)	H8A—C8—H8C	109.5
C9—O3—H3	109.5	H8B—C8—H8C	109.5
C9—C1—H1	108.1	C7—C8—H8D	109.5
C2—C1—H1	108.1	H8A—C8—H8D	141.0
C6—C1—H1	108.1	H8B—C8—H8D	56.2
C7—C2—H2A	108.3	H8C—C8—H8D	56.3
C1—C2—H2A	108.3	C7—C8—H8E	109.5
C3—C2—H2A	108.3	H8A—C8—H8E	56.3
C4—C3—H3A	109.2	H8B—C8—H8E	141.0
C2—C3—H3A	109.2	H8C—C8—H8E	56.2
C4—C3—H3B	109.2	H8D—C8—H8E	109.5
C2—C3—H3B	109.2	C7—C8—H8F	109.4
H3A—C3—H3B	107.9	H8A—C8—H8F	56.2
C5—C4—H4A	109.5	H8B—C8—H8F	56.3
C3—C4—H4A	109.5	H8C—C8—H8F	141.1
C5—C4—H4B	109.5	H8D—C8—H8F	109.5
C3—C4—H4B	109.5	H8E—C8—H8F	109.5
C9—C1—C2—C7	60.1 (3)	C2—C1—C6—C5	56.3 (3)
C6—C1—C2—C7	−177.61 (18)	C1—C2—C7—O1	13.8 (3)
C9—C1—C2—C3	−177.8 (2)	C3—C2—C7—O1	−108.8 (3)
C6—C1—C2—C3	−55.5 (2)	C1—C2—C7—C8	−167.6 (2)
C7—C2—C3—C4	179.4 (2)	C3—C2—C7—C8	69.8 (3)
C1—C2—C3—C4	55.6 (3)	C2—C1—C9—O2	26.0 (3)
C2—C3—C4—C5	−55.5 (3)	C6—C1—C9—O2	−97.5 (3)
C3—C4—C5—C6	55.6 (3)	C2—C1—C9—O3	−157.3 (2)
C4—C5—C6—C1	−56.2 (3)	C6—C1—C9—O3	79.2 (3)
C9—C1—C6—C5	−179.3 (2)