The anti­oxidant methyl 3-(3,5-di-tert-butyl-4-hy­droxy­phen­yl)propionate

The title compound, C₁₈H₂₈O₃, was prepared by the reaction of 2,6-di-tert-butyl­phenol with methyl acrylate under basic conditions using di­methyl sulfoxide as the promoter. The structure of this anti­oxidant indicates significant strain between the ortho tert-butyl substituents and the phenolic OH group. In spite of the steric crowding of the OH group, it participates in inter­molecular hydrogen bonding with the ester carbonyl O atom.

S1. Introduction

Many organic materials, such as lubricants, fuels and polymers, are susceptible to oxidative and thermal deterioration from heat, mechanical stress, and in the presence of chemicals such as atmospheric oxygen or metallic impurities (Strlič et al., 2009). This may result in the loss of the desirable physical properties of these materials and the failure of their proper functions. For example, lubricants undergo thermal degradation when used during periods of elevated temperature, forming resins and sludges. One way to retard the deterioration is to incorporate an anti­oxidant as a stabilizer into these materials (Seguchi et al., 2012). Sterically hindered hy­droxy­lphenyl­carb­oxy­lic acid esters have attracted considerable inter­est in this regard. They have been widely used in polymer processing, and in industrial and automotive lubricating oils and greases (Bertoldo & Ciardelli, 2004). The excellent anti­oxidant properties of sterically hindered hy­droxy­phenyl­carb­oxy­lic acid esters ensure process stability, long-term thermal stability of polymers and durability of the corresponding products. They also enhance the performance of lubricant formulations by improving thermal stability, enabling longer oil drains, and providing extended equipment life. Continued efforts have been devoted to developing and improving the preparation processes of these hindered hy­droxy­phenyl­carb­oxy­lic acid esters to be more environmentally benign and cost effective (Baranski, 2008).

Methyl 3-(3,5-di-tert-butyl-4-hy­droxy­phenyl)­propionate, (I), is one of the most important hindered hy­droxy­phenyl­carb­oxy­lic acid esters, because not only is it an effective anti­oxidant itself, but it is also a key starting material for the preparation of many other anti­oxidants through transesterification reaction with other alcohols (Fung et al., 2014; Gatto et al., 2010). There are many publications concerning the synthesis (Volod'kin & Zaikov, 2006, 2012), the reaction kinetics (Volod'kin & Zaikov, 2002, 2007a or 2007b ?; Zaikov & Volod'kin, 2004) and the anti­oxidation mechanism (Volod'kin et al., 1990; Volod'kin & Zaikov, 2007a or 2007b ?, 2011), but the crystal structure of (I) has not yet been reported. As part of our ongoing studies of the synthesis and properties of hindered phenol anti­oxidants, we report herein the crystal structure of the title compound, (I).

S2. Experimental

S2.1. Synthesis and crystallization

The title compound was synthesized by a modification of Gatto's procedure (Gatto et al., 2010). Thus, 2,6-di-tert-butyl­phenol (98%, Aladdin), sodium hydroxide (>=96%, Sinopharm) and di­methyl­sulfoxide (>99%, Aladdin) were mixed and stirred at about 353 K for about 30 min under argon gas, followed by the removal of water under vacuum. Methyl acrylate (98.5%, Aladdin) was then added dropwise to the reaction mixture at an elevated temperature and the reaction kept under argon for a few hours to give a deep-red solution. The solution was cooled to room temperature and AcOH was added to neutralize the base. MeOH and H₂O were added and the mixture stirred at room temperature for about 30 min, and then left standing at room temperature for a few hours. A pale-yellow solid precipitated, which was filtered off to give the crude product as a pale-yellow solid. Recrystallization from hexane gave (I) as single crystals suitable for X-ray analysis.

S2.2. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1. C-bound H atoms were placed in geometrically calculated positions, with C—H = 0.93 Å for aromatic H, 0.96 Å for methyl H and 0.97 Å for methyl­ene H atoms, and were included in the refinement in the riding-model approximation, with U_iso(H) = 1.2U_eq(C) for aromatic or methyl­ene H and 1.5U_eq(C) for methyl H atoms [Text amended to include details for all three C-bound H-atom types. Please check carefully]. O-bound H atoms were found in a difference Fourier synthesis and were also included in the riding-model approximation, with the O—H distances fixed as initially found and with U_iso(H) = 1.5U_eq(O).

S3. Results and discussion

Compound (I) crystallizes in the monoclinic space group P2₁/c. The atomic numbering and displacement ellipsoid plot are presented in Fig. 1. Selected bond distances, angles and torsion angles are presented in Table 2. There are some common features of the molecular structure of (I) which compare with similar compounds, including 2,6-di-tert-butyl­phenol (Lutz & Spek, 2005), 2,6-di-tert-butyl-4-methyl­phenol (Iimura et al., 1983), 2,6-di-tert-butyl-4-meth­oxy­phenol (Burton et al., 1980) and 2,6-di-tert-butyl-4-(3-chloro-2-hy­droxy­propyl)­phenol (Asgarova et al., 2011). (i) The bond distances within the aromatic ring and the phenolic C—O bonds are similar. (ii) The density of the crystal is fairly low, consistent with there being no significant inter­molecular π–π stacking or C—H···π inter­actions. (iii) Significant deformations are observed for some of the bond angles within the tert-butyl groups which are significantly different from standard values. These deformations reduce the intra­molecular crowding of the two bulky tert-butyl groups which are located ortho to the hydroxyl group in the benzene ring. (iv) The tert-butyl groups are situated so that one of the methyl groups (C12 or C18, respectively, for the two tert-butyl groups) is near the benzene plane and the other two methyl groups (C13 and C14 or C16 and C17) face the hydroxyl group. For example, in (I) the torsion angles C1—C2—C11—C12 and C5—C4—C15—C18 are -1.2 (3) and 1.0 (3)°, respectively. The r.m.s. deviation of the fitted atoms of the aromatic ring is 0.003 Å and atoms C11, C12, C15, C18 and C7 deviate from this mean plane by 0.007 (2)–0.067 (3) Å. (v) The hydroxyl group is close to coplanar with the benzene ring, with a C4—C3—O1—H1 torsion angle of 13.2 (3)°. This conformation is not only consistent with previous findings in similar molecules, but is also in agreement with high-level ab initio calculations (Ribeiro da Silva et al., 1999) and is presumably adopted as it allows effective conjugation of the oxygen p-type lone-pair electrons with the aromatic ring.

The near coplanarity of the OH group with the aromatic ring leads to short intra­molecular H···H contacts with one of the tert-butyl groups (C15–C18). The shortest H···H distances are 2.064 Å to H16B and 1.772 Å to H17A. Accordingly, the C15—C16 and C15—C17 bond lengths [1.539 (3) and 1.537 (3) Å, respectively] are slightly longer than the corresponding C—C bonds of the second tert-butyl group [C11—C13 = 1.526 (3) and C11—C14 = 1.534 (3) Å, respectively]. The congestion around the OH group is manifest in an opening up of the C4—C3—O1 bond angle to 121.6 (2)° and a closing up of the C2—C3—O1 bond angle to 115.7 (2)°, in addition to a stretching of the C2—C3 [1.408 (3) Å] and C3—C4 [1.400 (3) Å] bonds compared with the remaining aromatic C—C bond distances [C1—C2 = 1.383 (3), C1—C6 = 1.382 (3), C4—C5 = 1.389 (3) and C5—C6 = 1.381 (3) Å]. These structural deformations serve to relieve non-bonded repulsion between the O—H group and the relevant H atoms attached to C13, C14, C16 and C17. The nearest-neighbour distances between the O atom and the H atoms of the two tert-butyl groups are O1···H14C = 2.333 and O1···H16B = 2.487 Å.

It is noteworthy that atoms C11 and C15, which are linked directly to the aromatic group in the ortho positions to the hydroxyl group, have slightly longer bond lengths [1.541 (3) and 1.545 (3) Å, respectively] than all other C—C bonds (in the range 1.526–1.539 Å) of the two tert-butyl groups. However, atom C7, which is linked directly to the same aromatic group in the para position of the hydroxyl group, has a significantly shorter bond length [1.512 (3) Å]. This reflects the response of the C(Ar)—CMe₃ bond distances to the steric inter­actions between the bulky substituents and the aromatic ring. Inter­estingly, a previous report shows that tert-butyl groups in the ortho positions of phenols can be easily removed through an acid-catalysed retro Friedel–Crafts alkyl­ation reaction (Tashiro et al., 1978), a process which relieves this steric strain.

Fig. 1 shows that the molecule of (I) adopts an extended conformation, with the C6—C7—C8—C9 dihedral angle = -173.5 (2)° and the C5—C6—C7—C8 dihedral angle = -78.0 (3)°, avoiding possible steric inter­actions between the propionate substituent and the aromatic ring. This possibly reflects some hyperconjugation between the C7—C8 bond and the aromatic ring. In the methyl ester group, atoms C10, O3, C9, O2 and C8 are coplanar, with torsion angles of C10—O3—C9—O2 = 1.6 (4)° and C10—O3—C9—C8 = -179.4 (2)°. It is worth mentioning that the C atom linked directly to the benzene ring at the para position to the OH group has a bond distance of 1.512 (3) Å (C6—C7), which is slightly longer than the corresponding distances in 2,6-di-tert-butyl-4-methyl­phenol (Iimura et al., 1983) and 2,6-di-tert-butyl-4-(3-chloro-2-hy­droxy­propyl)­phenol (Asgarova et al., 2011). This suggests that there is decreased hyperconjugation between the methyl­ene and the benzene ring, which may reflect the electron-withdrawing nature of the methyl ester group at the end of the molecule.

One particular inter­est for us in studying the crystal structure of (I) is to investigate whether the phenolic OH group participates in hydrogen bonding, since the two bulky tert-butyl groups located in the two ortho positions of the phenol may hinder this inter­action. There have been relatively few cases of 2,6-di-tert-butyl-substituted phenols showing hydrogen bonding (Lutz & Spek, 2005). Nevertheless, hydrogen bonding, either inter- or intra­molecular, typically plays an important role in the structure and properties of these compounds. Substituted hindered phenols are typically good anti­oxidants, the function of which is to inter­cept and react with free radicals at a rate faster than the reaction between free radicals and the substrate (Ozawa, 1997; Harman, 1981). The mechanism has previously been proposed as H-atom transfer (Wright et al., 2001), shown below [Initiation, addition of O₂, H-atom exchange - these diagrams have not been received. Please send by email].

The role of an anti­oxidant, ArOH, is to inter­rupt the chain reaction by donating the phenolic H atom to form a stable phenolic radical. The more stable the radical the more effective is the anti­oxidant (Leopoldini et al., 2004). It is well known that the phenolic O—H bond is weaker if bulky substituents such as tert-butyl groups are introduced at the two ortho positions (Lucarini et al., 1996), and this is very likely due to the relief of strain when the OH H atom is lost. Thus, when two tert-butyl groups are located at the ortho positions to the hydroxyl group of the molecule, this makes the O—H bond much easier to break and, in addition, provides both steric and electronic stabilisation to the resulting phen­oxy radical. Therefore, it is of inter­est to obtain information on the conformation of the phenolic OH group in (I), which has two bulky tert-butyl groups in the ortho positions and an alkyl-methyl ester group in the para position.

Despite the steric shielding of the two tert-butyl groups on both sides of the OH group, (I) forms a weak inter­molecular hydrogen bond, in which O1—H1 serves as the donor and carbonyl atom O2 of the ester group of an adjacent molecule serves as the acceptor. These hydrogen bonds are shown as dashed lines in Fig. 2 and geometric details are given in Table 3. This inter­molecular hydrogen-bond inter­action with neighbouring molecules results in the formation of hydrogen-bonded chains extending in the crystallographic b direction, as shown in Fig. 2.

As discussed above, congestion around the OH group due to the presence of the two ortho tert-butyl groups results in significant non-bonded inter­actions between the phenol H atom and the neighbouring C—H groups, and is no doubt an important factor contributing to the weakness of the O—H bond. The strength of the O—H bond is a major factor contributing to its useful anti­oxidant properties.

Related literature

For related literature, see: Asgarova et al. (2011); Baranski (2008); Bertoldo & Ciardelli (2004); Burton et al. (1980); Fung et al. (2014); Gatto et al. (2010); Harman (1981); Iimura et al. (1983); Leopoldini et al. (2004); Lucarini et al. (1996); Lutz & Spek (2005); Ozawa (1997); Seguchi et al. (2012); Strlič et al. (2009); Tashiro et al. (1978); Volod'kin & Zaikov (2002, 2006, 2012); Volod'kin, Zaitsev, Rubyailo, Belyakov & Zaikov (1990); Wright et al. (2001); Zaikov & Volod'kin (2004).

Computing details

Data collection: SMART (Bruker, 1997); cell refinement: SAINT (Bruker, 1999); data reduction: SAINT (Bruker, 1999); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. A view of the molecule of (I), with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry codes: (i) x + 1, y, z; (ii) -x + 1, y - 1/2, -z + 1/2.]
	Fig. 2. Crystal packing diagram for (I). Dashed lines show the intermolecular hydrogen-bonding interactions.

Methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate

Crystal data

C18H28O3	F(000) = 640
Mr = 292.40	Dx = 1.100 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 5.9191 (14) Å	Cell parameters from 1787 reflections
b = 18.164 (4) Å	θ = 5.0–45.6°
c = 16.605 (4) Å	µ = 0.07 mm^−1
β = 98.343 (6)°	T = 293 K
V = 1766.4 (7) Å^3	Prismatic, colourless
Z = 4	0.21 × 0.15 × 0.11 mm

Data collection

Bruker SMART CCD area-detector diffractometer	3224 independent reflections
Radiation source: fine-focus sealed tube	2155 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.039
ϕ and ω scans	θmax = 25.4°, θmin = 1.7°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −7→7
Tmin = 0.591, Tmax = 0.746	k = −18→21
10007 measured reflections	l = −15→20

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)] = 0.054	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.164	H atoms treated by a mixture of independent and constrained refinement
S = 1.07	w = 1/[σ^2(Fo^2) + (0.0802P)^2 + 0.2237P] where P = (Fo^2 + 2Fc^2)/3
3224 reflections	(Δ/σ)max < 0.001
198 parameters	Δρmax = 0.23 e Å^−3
0 restraints	Δρmin = −0.19 e Å^−3

Special details

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	0.2878 (3)	0.27812 (8)	0.33694 (10)	0.0699 (5)
H1	0.3618	0.2406	0.3323	0.105*
O2	0.6255 (3)	0.64083 (9)	0.06254 (12)	0.0914 (6)
O3	0.9655 (3)	0.59379 (10)	0.05976 (12)	0.0961 (6)
C1	0.3321 (3)	0.45709 (10)	0.24595 (11)	0.0490 (5)
H1A	0.2943	0.5057	0.2556	0.059*
C2	0.2843 (3)	0.40351 (10)	0.30023 (10)	0.0441 (5)
C3	0.3436 (3)	0.33064 (10)	0.28341 (11)	0.0449 (5)
C4	0.4484 (3)	0.31184 (10)	0.21592 (11)	0.0459 (5)
C5	0.4906 (3)	0.36922 (11)	0.16486 (11)	0.0512 (5)
H5	0.5606	0.3584	0.1196	0.061*
C6	0.4337 (3)	0.44152 (10)	0.17805 (11)	0.0493 (5)
C7	0.4840 (4)	0.50247 (12)	0.12122 (12)	0.0618 (6)
H7A	0.4429	0.4856	0.0656	0.074*
H7B	0.3873	0.5443	0.1289	0.074*
C8	0.7239 (4)	0.52749 (14)	0.13217 (16)	0.0806 (7)
H8A	0.8192	0.4874	0.1182	0.097*
H8B	0.7709	0.5392	0.1891	0.097*
C9	0.7639 (4)	0.59316 (13)	0.08212 (13)	0.0626 (6)
C10	1.0221 (5)	0.65549 (18)	0.01166 (19)	0.1028 (10)
H10A	0.9384	0.6519	−0.0422	0.154*
H10B	1.1829	0.6551	0.0087	0.154*
H10C	0.9827	0.7005	0.0365	0.154*
C11	0.1727 (3)	0.42419 (11)	0.37542 (11)	0.0503 (5)
C12	0.1328 (5)	0.50727 (13)	0.37994 (14)	0.0810 (8)
H12A	0.0307	0.5228	0.3328	0.121*
H12B	0.2758	0.5326	0.3818	0.121*
H12C	0.0670	0.5184	0.4281	0.121*
C13	−0.0591 (4)	0.38666 (15)	0.37253 (16)	0.0812 (8)
H13A	−0.1565	0.4008	0.3237	0.122*
H13B	−0.1276	0.4013	0.4190	0.122*
H13C	−0.0390	0.3342	0.3731	0.122*
C14	0.3312 (4)	0.40281 (15)	0.45330 (12)	0.0754 (7)
H14A	0.2629	0.4172	0.4999	0.113*
H14B	0.4753	0.4273	0.4545	0.113*
H14C	0.3545	0.3505	0.4542	0.113*
C15	0.5157 (4)	0.23204 (11)	0.19761 (12)	0.0537 (5)
C16	0.3028 (4)	0.18252 (13)	0.18234 (17)	0.0779 (7)
H16A	0.1991	0.2016	0.1373	0.117*
H16B	0.2290	0.1816	0.2301	0.117*
H16C	0.3475	0.1335	0.1700	0.117*
C17	0.6896 (4)	0.20143 (12)	0.26731 (14)	0.0668 (6)
H17A	0.6190	0.1972	0.3156	0.100*
H17B	0.8179	0.2342	0.2773	0.100*
H17C	0.7404	0.1538	0.2525	0.100*
C18	0.6314 (5)	0.22816 (13)	0.12084 (15)	0.0760 (7)
H18A	0.6737	0.1782	0.1117	0.114*
H18B	0.7656	0.2586	0.1279	0.114*
H18C	0.5275	0.2453	0.0749	0.114*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0834 (12)	0.0514 (9)	0.0823 (10)	0.0044 (8)	0.0366 (8)	0.0161 (8)
O2	0.0915 (14)	0.0669 (11)	0.1237 (15)	0.0108 (10)	0.0420 (11)	0.0242 (10)
O3	0.0614 (11)	0.1071 (15)	0.1235 (15)	0.0082 (10)	0.0256 (10)	0.0522 (12)
C1	0.0581 (12)	0.0403 (10)	0.0486 (10)	0.0040 (9)	0.0081 (9)	0.0009 (8)
C2	0.0454 (11)	0.0450 (11)	0.0412 (9)	0.0019 (8)	0.0041 (8)	−0.0014 (8)
C3	0.0457 (11)	0.0421 (10)	0.0473 (10)	−0.0019 (8)	0.0080 (8)	0.0046 (8)
C4	0.0454 (11)	0.0426 (11)	0.0498 (10)	−0.0013 (8)	0.0076 (8)	−0.0040 (8)
C5	0.0571 (13)	0.0567 (13)	0.0414 (10)	0.0006 (10)	0.0129 (8)	−0.0013 (9)
C6	0.0568 (12)	0.0472 (11)	0.0436 (10)	0.0010 (9)	0.0060 (8)	0.0058 (8)
C7	0.0740 (16)	0.0583 (13)	0.0532 (11)	−0.0018 (11)	0.0101 (10)	0.0119 (10)
C8	0.0705 (17)	0.0805 (17)	0.0910 (17)	−0.0016 (13)	0.0121 (13)	0.0347 (14)
C9	0.0635 (15)	0.0619 (14)	0.0625 (13)	−0.0011 (12)	0.0093 (11)	0.0090 (11)
C10	0.0779 (19)	0.120 (3)	0.114 (2)	−0.0124 (16)	0.0240 (16)	0.0507 (19)
C11	0.0535 (12)	0.0534 (12)	0.0453 (10)	0.0023 (9)	0.0115 (8)	−0.0045 (9)
C12	0.110 (2)	0.0679 (16)	0.0708 (15)	0.0186 (14)	0.0341 (14)	−0.0099 (12)
C13	0.0591 (15)	0.101 (2)	0.0887 (17)	−0.0084 (14)	0.0293 (12)	−0.0220 (15)
C14	0.0812 (17)	0.0984 (19)	0.0465 (12)	0.0121 (14)	0.0096 (11)	−0.0055 (11)
C15	0.0535 (12)	0.0446 (11)	0.0649 (13)	0.0000 (9)	0.0154 (10)	−0.0076 (9)
C16	0.0681 (16)	0.0576 (14)	0.1089 (19)	−0.0078 (12)	0.0159 (13)	−0.0242 (13)
C17	0.0645 (15)	0.0521 (13)	0.0852 (16)	0.0110 (11)	0.0151 (12)	0.0014 (11)
C18	0.0912 (19)	0.0639 (15)	0.0781 (16)	0.0110 (13)	0.0298 (13)	−0.0145 (12)

Geometric parameters (Å, º)

O1—C3	1.376 (2)	C11—C12	1.531 (3)
O1—H1	0.820 (17)	C11—C13	1.526 (3)
O2—C9	1.204 (3)	C11—C14	1.533 (3)
O3—C9	1.300 (3)	C12—H12A	0.9600
O3—C10	1.444 (3)	C12—H12B	0.9600
C1—C6	1.382 (3)	C12—H12C	0.9600
C1—C2	1.383 (3)	C13—H13A	0.9600
C1—H1A	0.9300	C13—H13B	0.9600
C2—C3	1.408 (3)	C13—H13C	0.9600
C2—C11	1.541 (3)	C14—H14A	0.9600
C3—C4	1.400 (3)	C14—H14B	0.9600
C4—C5	1.389 (3)	C14—H14C	0.9600
C4—C15	1.545 (3)	C15—C16	1.539 (3)
C5—C6	1.381 (3)	C15—C17	1.537 (3)
C5—H5	0.9300	C15—C18	1.534 (3)
C6—C7	1.512 (3)	C16—H16A	0.9600
C7—C8	1.477 (3)	C16—H16B	0.9600
C7—H7A	0.9700	C16—H16C	0.9600
C7—H7B	0.9700	C17—H17A	0.9600
C8—C9	1.492 (3)	C17—H17B	0.9600
C8—H8A	0.9700	C17—H17C	0.9600
C8—H8B	0.9700	C18—H18A	0.9600
C10—H10A	0.9600	C18—H18B	0.9600
C10—H10B	0.9600	C18—H18C	0.9600
C10—H10C	0.9600
C3—O1—H1	109.5 (17)	C12—C11—C2	111.54 (16)
C9—O3—C10	117.5 (2)	C14—C11—C2	109.86 (16)
C6—C1—C2	122.82 (18)	C11—C12—H12A	109.5
C6—C1—H1A	118.6	C11—C12—H12B	109.5
C2—C1—H1A	118.6	H12A—C12—H12B	109.5
C1—C2—C3	116.86 (17)	C11—C12—H12C	109.5
C1—C2—C11	120.57 (16)	H12A—C12—H12C	109.5
C3—C2—C11	122.57 (16)	H12B—C12—H12C	109.5
O1—C3—C2	115.69 (16)	C11—C13—H13A	109.5
O1—C3—C4	121.59 (16)	C11—C13—H13B	109.5
C4—C3—C2	122.71 (16)	H13A—C13—H13B	109.5
C5—C4—C3	116.47 (17)	C11—C13—H13C	109.5
C5—C4—C15	120.62 (17)	H13A—C13—H13C	109.5
C3—C4—C15	122.91 (16)	H13B—C13—H13C	109.5
C6—C5—C4	123.17 (18)	C11—C14—H14A	109.5
C6—C5—H5	118.4	C11—C14—H14B	109.5
C4—C5—H5	118.4	H14A—C14—H14B	109.5
C5—C6—C1	117.97 (17)	C11—C14—H14C	109.5
C5—C6—C7	121.51 (18)	H14A—C14—H14C	109.5
C1—C6—C7	120.52 (18)	H14B—C14—H14C	109.5
C8—C7—C6	114.92 (18)	C18—C15—C16	106.86 (18)
C8—C7—H7A	108.5	C18—C15—C17	106.16 (18)
C6—C7—H7A	108.5	C16—C15—C17	110.82 (18)
C8—C7—H7B	108.5	C18—C15—C4	111.44 (17)
C6—C7—H7B	108.5	C16—C15—C4	110.62 (17)
H7A—C7—H7B	107.5	C17—C15—C4	110.78 (16)
C7—C8—C9	113.9 (2)	C15—C16—H16A	109.5
C7—C8—H8A	108.8	C15—C16—H16B	109.5
C9—C8—H8A	108.8	H16A—C16—H16B	109.5
C7—C8—H8B	108.8	C15—C16—H16C	109.5
C9—C8—H8B	108.8	H16A—C16—H16C	109.5
H8A—C8—H8B	107.7	H16B—C16—H16C	109.5
O2—C9—O3	122.2 (2)	C15—C17—H17A	109.5
O2—C9—C8	124.7 (2)	C15—C17—H17B	109.5
O3—C9—C8	113.1 (2)	H17A—C17—H17B	109.5
O3—C10—H10A	109.5	C15—C17—H17C	109.5
O3—C10—H10B	109.5	H17A—C17—H17C	109.5
H10A—C10—H10B	109.5	H17B—C17—H17C	109.5
O3—C10—H10C	109.5	C15—C18—H18A	109.5
H10A—C10—H10C	109.5	C15—C18—H18B	109.5
H10B—C10—H10C	109.5	H18A—C18—H18B	109.5
C13—C11—C12	107.3 (2)	C15—C18—H18C	109.5
C13—C11—C14	110.51 (19)	H18A—C18—H18C	109.5
C12—C11—C14	106.74 (18)	H18B—C18—H18C	109.5
C13—C11—C2	110.77 (16)
C6—C1—C2—C3	−0.2 (3)	C6—C7—C8—C9	−173.4 (2)
C6—C1—C2—C11	179.46 (17)	C10—O3—C9—O2	1.7 (4)
C1—C2—C3—O1	−178.07 (17)	C10—O3—C9—C8	−179.4 (2)
C11—C2—C3—O1	2.3 (3)	C7—C8—C9—O2	30.7 (4)
C1—C2—C3—C4	0.7 (3)	C7—C8—C9—O3	−148.2 (2)
C11—C2—C3—C4	−178.92 (16)	C1—C2—C11—C13	118.3 (2)
O1—C3—C4—C5	178.19 (17)	C3—C2—C11—C13	−62.1 (2)
C2—C3—C4—C5	−0.5 (3)	C1—C2—C11—C12	−1.2 (3)
O1—C3—C4—C15	−1.9 (3)	C3—C2—C11—C12	178.40 (19)
C2—C3—C4—C15	179.44 (17)	C1—C2—C11—C14	−119.3 (2)
C3—C4—C5—C6	−0.2 (3)	C3—C2—C11—C14	60.3 (2)
C15—C4—C5—C6	179.83 (18)	C5—C4—C15—C18	1.1 (3)
C4—C5—C6—C1	0.7 (3)	C3—C4—C15—C18	−178.90 (18)
C4—C5—C6—C7	179.62 (18)	C5—C4—C15—C16	−117.7 (2)
C2—C1—C6—C5	−0.5 (3)	C3—C4—C15—C16	62.4 (2)
C2—C1—C6—C7	−179.42 (18)	C5—C4—C15—C17	119.0 (2)
C5—C6—C7—C8	−78.0 (3)	C3—C4—C15—C17	−60.9 (2)
C1—C6—C7—C8	100.8 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O2^i	0.82	2.51	3.003 (2)	120
C10—H10B···O2^ii	0.96	2.65	3.558 (4)	157

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