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The title compound, C14H22O, was studied at 110 K. The phenolic hydroxy group was found to be coplanar with the benzene ring and, due to steric hindrance from the tert-butyl groups, this hydroxy group does not form hydrogen bonds. The shortest inter­molecular O...O distance is 3.1008 (11) Å, with an O—H...O angle of 117.3 (16)°. There are no significant inter­molecular π–π stacking or C—H...π inter­actions.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270105030325/gg1284sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270105030325/gg1284Isup2.hkl
Contains datablock I

CCDC reference: 290571

Comment top

Our interest in the structure of the title compound (I) was aroused by the crystal structure of 5-(3,5-di-tert-butyl-4-hydroxybenzylidene)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione [compound (II); compound (V) in Rezende et al., 2005]. Compound (II) features an OH moiety that does not appear to form a hydrogen bond, with closest O···O distances of 3.391 (2) and 3.010 (2) Å for the two independent molecules in (II). Cases like this are rare. The Cambridge Structural Database (CSD, Version?; Allen, 2002) was analysed for similar configurations. In most cases where OH groups do not donate hydrogen bonds, this is due to missing or misplaced H atoms. Only in sterically very congested situations is hydrogen bonding really impossible (see below).

Substituted phenols have a technical application as antioxidants. In the first step of the oxidation reaction, the phenolic H atom is released and a phenoxyl radical is formed. It is well known that the strength of the O—H bond is weaker if bulky substituents like tert-butyl groups are introduced in ortho positions, and also that the electronic influence of para-substituents is important (Lucarini et al., 1996). Therefore, it is essential to know the conformation of the OH group in (I), which has two bulky substituents in the ortho positions and only an H atom in the para position.

The title compound, (I), is related to (II) and its structure has been published previously by Lazarev et al. (1992) based on a room-temperature data collection. The H-atom position of the phenolic hydroxy group could not be determined in that structure. In order to determine this H-atom position reliably, we redetermined the structure at 110 K. All H atoms could be located in the difference Fourier map and were refined freely with isotropic displacement parameters.

The hydroxy group is in the plane of the phenyl ring, with a C6—C1—O1—H1O torsion angle of −0.4 (14)° (Fig. 1). This finding is in accordance with high-level ab initio calculations (Ribeiro da Silva et al., 1999) and with the crystal structures of most non-substituted phenols. The planarity is also consistent with the findings in the monoclinic form of 2,6-di-tert-butyl-4-methylphenol (space group C2/c, CSD refcodes MBPHOL01 and MBPHOL11), where the OH torsion angle is −1 or 4°, respectively, but the CSD contains additional polymorphs with OH torsion angles up to 30 and 26°, respectively (orthorhombic form, space group P212121, CSD refcodes MBPHOL02 and MBPHOL10). A second monoclinic polymorph (space group Cc, CSD refcode MBPHOL12) has a torsion angle of −3°. Contrary to our present results for (I), polarizability studies (Aroney et al., 1964), ESR experiments (Nemoto et al., 1981) and semi-empirical AM1 calculations (Brewster et al., 1994) suggest a nonplanarity of the OH group in (I).

Molecules of (I) have an approximate non-crystallographic mirror symmetry, with the phenyl ring and the OH group in the mirror plane with an r.m.s. deviation (Pilati & Forni, 1998) of 0.0328 Å. When the H atoms are ignored from this calculation, the molecule has an approximate C2v symmetry with an r.m.s. deviation of 0.0273 Å. A rigid-body analysis can be performed on the molecule using the program THMA11 (Schomaker & Trueblood, 1998). When the two tert-butyl groups are defined as independent rotors, low rigid-body R values of 0.062 (for all U values) and 0.046 (for diagonal U values) can be achieved. The C1—O1 distance corrected for rigid-body motion is 1.390 Å, compared with the uncorrected value of 1.3865 (12) Å.

The coplanarity of the OH group with the phenyl ring leads to very short intramolecular H···H contacts with one of the tert-butyl groups. The shortest H···H distances are 1.90 (2) Å to H14C and 1.92 (2) Å to H12C. Accordingly, the C11—C14 and C11—C12 distances of 1.5466 (15) and 1.5480 (16) Å, respectively, are the longest C—C bonds of the tert-butyl groups. The congestion around the OH group can also be seen in the C—C—O bond angles of 120.59 (9)° in the direction of the H···H interactions and 116.45 (8)° in the opposite direction, showing that the O atom is slightly bent away. These H···H interactions are certainly a reason for the weakness of the O—H bond.

Due to the steric shielding of the two tert-butyl groups, there is no intermolecular hydrogen bonding involving the OH group. Thus, the shortest intermolecular O···O distance is 3.1008 (11) Å, with an O—H···O angle of 117.3 (16)° (Fig. 2). As there are no hydrogen-bond acceptors in the molecule (apart from the phenolic OH itself), no intramolecular hydrogen bonding is present. Significant intermolecular ππ stacking and C—H···π interactions are not observed. Consequently, the density of the crystal is rather low and the packing index (Kitajgorodskij, 1973) is only 67.5%, which is on the lower end of the 65–75% range expected for organic solids (Dunitz, 1995).

A study of the CSD (update August 2005) gives 90 entries with one or more 2,6-di-tert-butyl-substituted phenol moieties. In 34 of these entries, the coordinates of the OH H atoms are not deposited on the CSD, and three additional entries were not considered because of disorder. Of the remaining 53 entries, 29 do not form any hydrogen bonds with the shielded OH group as donor. In 24 entries, the shielded OH group is a hydrogen-bond donor with various acceptor atoms in the crystal structure. In none of the 90 entries is there a hydrogen bond between shielded OH groups.

Experimental top

Single crystals for the diffraction experiment were obtained by slow evaporation of a solution of 2,6-di-tert-butylphenol (ACROS Organics) in ethanol.

Refinement top

The X-ray intensities were obtained with two different exposure times and rotation angles of 1°. 364 ϕ and 414 ω scans were measured with an exposure time of 40 s per frame, and 156 ϕ scans with an exposure time of 8 s per frame. All C-bound H atoms were refined freely with isotropic displacement parameters in order to demonstrate that the outcome of the free refinement of H1O is reliable.

Computing details top

Data collection: COLLECT (Nonius, 1999); cell refinement: PEAKREF (Schreurs, 2005); data reduction: EVALCCD (Duisenberg et al. 2003); program(s) used to solve structure: coordinates adapted from literature (Lazarev et al., 1992); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: PLATON.

Figures top
[Figure 1] Fig. 1. Displacement ellipsoid plot of (I). Ellipsoids are drawn at the 50% probability level and H atoms are drawn as small spheres of arbitrary radii.
[Figure 2] Fig. 2. The packing arrangement of (I) in the crystal, which is unfavourable for hydrogen bonding. [Symmetry code: (i) 1 − x, −y, 1 − z.]
2,6-Di-tert-butylphenol top
Crystal data top
C14H22OF(000) = 456
Mr = 206.32Dx = 1.080 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 13875 reflections
a = 7.1369 (2) Åθ = 2.2–27.5°
b = 18.6755 (6) ŵ = 0.07 mm1
c = 9.8009 (4) ÅT = 110 K
β = 103.694 (3)°Plate, yellow
V = 1269.19 (8) Å30.48 × 0.48 × 0.06 mm
Z = 4
Data collection top
Nonius KappaCCD area-detector
diffractometer
2912 independent reflections
Radiation source: rotating anode2409 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.031
ϕ and ω scansθmax = 27.5°, θmin = 2.2°
Absorption correction: multi-scan
(SADABS; Sheldrick, 2002)
h = 99
Tmin = 0.78, Tmax = 1.0k = 2324
27689 measured reflectionsl = 1212
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.037Hydrogen site location: difference Fourier map
wR(F2) = 0.100All H-atom parameters refined
S = 1.03 w = 1/[σ2(Fo2) + (0.0471P)2 + 0.4344P]
where P = (Fo2 + 2Fc2)/3
2912 reflections(Δ/σ)max = 0.001
224 parametersΔρmax = 0.33 e Å3
0 restraintsΔρmin = 0.18 e Å3
Crystal data top
C14H22OV = 1269.19 (8) Å3
Mr = 206.32Z = 4
Monoclinic, P21/cMo Kα radiation
a = 7.1369 (2) ŵ = 0.07 mm1
b = 18.6755 (6) ÅT = 110 K
c = 9.8009 (4) Å0.48 × 0.48 × 0.06 mm
β = 103.694 (3)°
Data collection top
Nonius KappaCCD area-detector
diffractometer
2912 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 2002)
2409 reflections with I > 2σ(I)
Tmin = 0.78, Tmax = 1.0Rint = 0.031
27689 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0370 restraints
wR(F2) = 0.100All H-atom parameters refined
S = 1.03Δρmax = 0.33 e Å3
2912 reflectionsΔρmin = 0.18 e Å3
224 parameters
Special details top

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
xyzUiso*/Ueq
O10.59379 (11)0.06999 (4)0.46293 (8)0.02165 (19)
C10.75172 (14)0.11423 (5)0.46966 (10)0.0158 (2)
C20.75369 (14)0.15427 (5)0.34740 (10)0.0159 (2)
C30.91446 (16)0.19748 (6)0.35162 (11)0.0199 (2)
C41.06521 (16)0.20153 (6)0.47096 (12)0.0219 (2)
C51.05789 (15)0.16235 (6)0.58973 (11)0.0201 (2)
C60.90145 (14)0.11771 (5)0.59324 (10)0.0166 (2)
C70.58678 (15)0.15051 (6)0.21439 (10)0.0184 (2)
C80.39702 (16)0.17560 (7)0.24882 (12)0.0245 (2)
C90.62340 (19)0.19935 (6)0.09685 (12)0.0256 (3)
C100.56499 (17)0.07353 (6)0.15534 (11)0.0224 (2)
C110.89510 (16)0.07443 (6)0.72660 (11)0.0197 (2)
C120.71931 (19)0.09670 (7)0.78393 (12)0.0266 (3)
C131.07468 (19)0.08910 (7)0.84618 (12)0.0289 (3)
C140.89455 (18)0.00696 (6)0.69739 (12)0.0241 (2)
H1O0.606 (3)0.0479 (10)0.540 (2)0.056 (5)*
H30.9234 (19)0.2256 (7)0.2717 (14)0.024 (3)*
H41.1758 (19)0.2320 (7)0.4714 (14)0.024 (3)*
H51.166 (2)0.1657 (7)0.6725 (14)0.027 (3)*
H8A0.362 (2)0.1468 (7)0.3251 (15)0.028 (3)*
H8B0.289 (2)0.1731 (8)0.1619 (16)0.035 (4)*
H8C0.407 (2)0.2261 (8)0.2783 (15)0.030 (4)*
H9A0.630 (2)0.2506 (9)0.1242 (16)0.037 (4)*
H9B0.513 (2)0.1930 (7)0.0130 (15)0.031 (4)*
H9C0.743 (2)0.1856 (7)0.0680 (14)0.027 (3)*
H10A0.458 (2)0.0717 (7)0.0700 (16)0.033 (4)*
H10B0.683 (2)0.0590 (7)0.1280 (15)0.030 (3)*
H10C0.540 (2)0.0379 (8)0.2267 (15)0.031 (4)*
H12A0.729 (2)0.1485 (8)0.8103 (15)0.037 (4)*
H12B0.718 (2)0.0677 (8)0.8703 (16)0.036 (4)*
H12C0.589 (2)0.0893 (8)0.7161 (16)0.037 (4)*
H13A1.083 (2)0.1410 (8)0.8764 (15)0.035 (4)*
H13B1.064 (2)0.0587 (8)0.9300 (16)0.036 (4)*
H13C1.200 (2)0.0739 (8)0.8194 (16)0.037 (4)*
H14A0.902 (2)0.0345 (8)0.7852 (16)0.034 (4)*
H14B1.008 (2)0.0198 (8)0.6609 (15)0.035 (4)*
H14C0.780 (2)0.0250 (8)0.6269 (16)0.036 (4)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0206 (4)0.0265 (4)0.0166 (4)0.0068 (3)0.0018 (3)0.0055 (3)
C10.0164 (5)0.0152 (5)0.0163 (5)0.0006 (4)0.0051 (4)0.0015 (4)
C20.0195 (5)0.0155 (5)0.0133 (5)0.0013 (4)0.0051 (4)0.0015 (4)
C30.0255 (5)0.0187 (5)0.0178 (5)0.0025 (4)0.0096 (4)0.0001 (4)
C40.0213 (5)0.0213 (5)0.0244 (5)0.0055 (4)0.0082 (4)0.0041 (4)
C50.0194 (5)0.0203 (5)0.0194 (5)0.0012 (4)0.0021 (4)0.0042 (4)
C60.0201 (5)0.0152 (5)0.0146 (5)0.0018 (4)0.0042 (4)0.0016 (4)
C70.0221 (5)0.0186 (5)0.0140 (5)0.0006 (4)0.0033 (4)0.0013 (4)
C80.0232 (5)0.0277 (6)0.0217 (5)0.0056 (4)0.0034 (4)0.0024 (5)
C90.0354 (6)0.0253 (6)0.0154 (5)0.0015 (5)0.0043 (5)0.0042 (4)
C100.0267 (6)0.0215 (5)0.0167 (5)0.0003 (4)0.0008 (4)0.0013 (4)
C110.0260 (5)0.0180 (5)0.0134 (5)0.0001 (4)0.0015 (4)0.0006 (4)
C120.0389 (7)0.0258 (6)0.0182 (5)0.0008 (5)0.0127 (5)0.0009 (4)
C130.0376 (7)0.0248 (6)0.0183 (5)0.0036 (5)0.0057 (5)0.0014 (4)
C140.0302 (6)0.0182 (5)0.0209 (5)0.0010 (4)0.0000 (5)0.0004 (4)
Geometric parameters (Å, º) top
O1—C11.3865 (12)C9—H9A0.992 (16)
O1—H1O0.845 (19)C9—H9B1.003 (14)
C1—C61.4144 (13)C9—H9C0.996 (14)
C1—C21.4152 (14)C10—H10A0.990 (15)
C2—C31.3954 (14)C10—H10B0.982 (15)
C2—C71.5453 (14)C10—H10C1.010 (15)
C3—C41.3913 (15)C11—C131.5427 (15)
C3—H30.958 (14)C11—C141.5466 (15)
C4—C51.3863 (15)C11—C121.5480 (16)
C4—H40.972 (14)C12—H12A1.000 (15)
C5—C61.4003 (14)C12—H12B1.007 (16)
C5—H50.982 (14)C12—H12C1.017 (15)
C6—C111.5466 (14)C13—H13A1.012 (15)
C7—C91.5394 (15)C13—H13B1.015 (15)
C7—C101.5439 (15)C13—H13C1.029 (16)
C7—C81.5441 (15)C14—H14A0.993 (15)
C8—H8A0.999 (14)C14—H14B0.989 (16)
C8—H8B1.006 (15)C14—H14C0.995 (15)
C8—H8C0.985 (15)
C1—O1—H1O109.7 (12)C7—C9—H9C111.7 (8)
O1—C1—C6120.59 (9)H9A—C9—H9C109.7 (12)
O1—C1—C2116.45 (8)H9B—C9—H9C107.4 (11)
C6—C1—C2122.95 (9)C7—C10—H10A109.8 (8)
C3—C2—C1116.96 (9)C7—C10—H10B110.0 (8)
C3—C2—C7121.03 (9)H10A—C10—H10B107.4 (11)
C1—C2—C7122.02 (9)C7—C10—H10C111.9 (8)
C4—C3—C2121.55 (10)H10A—C10—H10C109.7 (11)
C4—C3—H3118.0 (8)H10B—C10—H10C107.9 (11)
C2—C3—H3120.4 (8)C13—C11—C14106.28 (9)
C5—C4—C3120.12 (10)C13—C11—C6111.34 (9)
C5—C4—H4119.8 (8)C14—C11—C6110.88 (9)
C3—C4—H4120.1 (8)C13—C11—C12105.99 (9)
C4—C5—C6121.58 (10)C14—C11—C12111.38 (9)
C4—C5—H5118.7 (8)C6—C11—C12110.78 (8)
C6—C5—H5119.7 (8)C11—C12—H12A109.9 (9)
C5—C6—C1116.84 (9)C11—C12—H12B109.3 (8)
C5—C6—C11121.00 (9)H12A—C12—H12B108.5 (12)
C1—C6—C11122.17 (9)C11—C12—H12C114.9 (9)
C9—C7—C10106.93 (9)H12A—C12—H12C107.3 (12)
C9—C7—C8107.27 (9)H12B—C12—H12C106.6 (12)
C10—C7—C8110.41 (9)C11—C13—H13A112.0 (8)
C9—C7—C2111.77 (9)C11—C13—H13B108.0 (8)
C10—C7—C2110.34 (8)H13A—C13—H13B108.0 (12)
C8—C7—C2110.04 (8)C11—C13—H13C111.9 (8)
C7—C8—H8A112.7 (8)H13A—C13—H13C110.0 (12)
C7—C8—H8B109.7 (8)H13B—C13—H13C106.7 (12)
H8A—C8—H8B109.4 (11)C11—C14—H14A110.6 (9)
C7—C8—H8C110.3 (8)C11—C14—H14B109.8 (9)
H8A—C8—H8C108.1 (11)H14A—C14—H14B107.7 (12)
H8B—C8—H8C106.4 (11)C11—C14—H14C115.3 (8)
C7—C9—H9A112.0 (9)H14A—C14—H14C107.1 (12)
C7—C9—H9B107.6 (8)H14B—C14—H14C106.0 (12)
H9A—C9—H9B108.2 (12)
O1—C1—C2—C3178.28 (9)C2—C1—C6—C11179.01 (9)
C6—C1—C2—C31.28 (15)C3—C2—C7—C90.64 (13)
O1—C1—C2—C71.45 (14)C1—C2—C7—C9179.64 (9)
C6—C1—C2—C7178.99 (9)C3—C2—C7—C10118.21 (11)
C1—C2—C3—C40.54 (15)C1—C2—C7—C1061.51 (12)
C7—C2—C3—C4179.73 (10)C3—C2—C7—C8119.71 (11)
C2—C3—C4—C50.27 (16)C1—C2—C7—C860.57 (12)
C3—C4—C5—C60.40 (16)C5—C6—C11—C131.08 (14)
C4—C5—C6—C10.30 (15)C1—C6—C11—C13179.10 (9)
C4—C5—C6—C11179.88 (10)C5—C6—C11—C14117.04 (11)
O1—C1—C6—C5178.38 (9)C1—C6—C11—C1462.78 (13)
C2—C1—C6—C51.16 (14)C5—C6—C11—C12118.77 (11)
O1—C1—C6—C111.44 (14)C1—C6—C11—C1261.42 (12)

Experimental details

Crystal data
Chemical formulaC14H22O
Mr206.32
Crystal system, space groupMonoclinic, P21/c
Temperature (K)110
a, b, c (Å)7.1369 (2), 18.6755 (6), 9.8009 (4)
β (°) 103.694 (3)
V3)1269.19 (8)
Z4
Radiation typeMo Kα
µ (mm1)0.07
Crystal size (mm)0.48 × 0.48 × 0.06
Data collection
DiffractometerNonius KappaCCD area-detector
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 2002)
Tmin, Tmax0.78, 1.0
No. of measured, independent and
observed [I > 2σ(I)] reflections
27689, 2912, 2409
Rint0.031
(sin θ/λ)max1)0.649
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.037, 0.100, 1.03
No. of reflections2912
No. of parameters224
H-atom treatmentAll H-atom parameters refined
Δρmax, Δρmin (e Å3)0.33, 0.18

Computer programs: COLLECT (Nonius, 1999), PEAKREF (Schreurs, 2005), EVALCCD (Duisenberg et al. 2003), coordinates adapted from literature (Lazarev et al., 1992), SHELXL97 (Sheldrick, 1997), PLATON (Spek, 2003), PLATON.

Selected geometric parameters (Å, º) top
O1—C11.3865 (12)C2—C31.3954 (14)
O1—H1O0.845 (19)C3—C41.3913 (15)
C1—C61.4144 (13)C4—C51.3863 (15)
C1—C21.4152 (14)C5—C61.4003 (14)
C1—O1—H1O109.7 (12)O1—C1—C2116.45 (8)
O1—C1—C6120.59 (9)C6—C1—C2122.95 (9)
 

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