organic compounds
tert-Butyl 2-methyl-2-(4-methylbenzoyl)propanoate
aDepartment of Chemistry, 1400 Townsend Drive, Michigan Technological University, Houghton, MI 49931, USA
*Correspondence e-mail: rluck@mtu.edu
The title compound, C16H22O3, is bent with a dihedral angle of 75.3 (1)° between the mean planes of the benzene ring and a group encompassing the ester functionality (O=C—O—C). In the crystal, the molecules are linked into infinite chains held together by weak C—H⋯O hydrogen-bonded interactions between an H atom on the benzene ring of one molecule and an O atom on the ketone functionality of an adjacent molecule. The chains are arranged with neighbouring tert-butyl and dimethyl groups on adjacent chains exhibiting hydrophobic stacking, with short C—H⋯H—C contacts (2.37 Å) between adjacent chains
Related literature
For the synthesis, spectroscopic characterization and reactivity of the title compound, see: Logue (1974); Logue et al. (1975). For related structures, see: Crosse et al. (2010a,b; Logue et al. (2010). For the syntheses and characterization of structurally similar indanone-derived β-keto ester derivatives, see: Mouri et al. (2009); Noritake et al. (2008); Rigby & Dixon (2008). For weak hydrogen-bonded interactions, see: Karle et al. (2009). For H⋯H interactions, see: Alkorta et al. (2008).
Experimental
Crystal data
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Refinement
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Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994); cell CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SIR2004 (Burla et al., 2005); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and Mercury (Macrae et al., 2008); software used to prepare material for publication: WinGX (Farrugia, 1999) and publCIF (Westrip, 2010).
Supporting information
https://doi.org/10.1107/S1600536810003144/zl2266sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810003144/zl2266Isup2.hkl
Crystals of the material were synthesized as reported earlier and were grown by evaporation of a solution in hexane (Logue, 1974). IR (neat, cm-1): 3003 (w, C—H), 2974, 1734 (v.s., ester C=O), 1671 (v.s., ketone C=O) 1608 (m, C—C), 1455 (m), 1386 (m), 1366 (s), 1273 (s, alkyl methyl C—H), 1247 (s), 1130 (v.s., ester C—O), 986 (s), 921 (m), 836 (s, C—H bend), 740 (s). 1H NMR (CDCl3) δ; 1.28 (s, 9H), 1.47 (s, 6H), 2.37 (s, 3H), 7.19 (d, 2H, J=8.0 Hz), 7.76 (d, 2H, J=8.8 Hz). 13C NMR (CDCl3) δ; 21.7, 24.1, 27.8, 54.1, 81.8, 129.2, 132.9, 143.5, 174.4, 198.9.
All H atoms were placed at calculated positions, with C—H = 0.93 Å (aromatic) or 0.96 Å (methyl) and refined using a riding model with Uiso(H) constrained to be 1.5 Ueq(C) for methyl groups and 1.2 Ueq(C) for all other C atoms. The quality of the data as reflected by only 48% of the reflections observed, large ADP's and inaccurate C—C bond lengths is low. The data had been collected on a 30 year old single point detector instrument not equipped with a low temperature device as part of a class project with undergraduate students. Due to the time constraints imposed by the class schedule a maximum exposure time of 60 s had to be alloted for measuring each reflection.
There are close contacts (i.e., <2.4 Å, (Alkorta et al., 2008)) between an H atom on C11 and one on the C18 atom of an adjacent molecule, Fig. 2. These contacts remain present irrespective of if all the H atoms are refined freely (which generates reasonable parameters) or if they are refined generated either with the AFIX 33 or AFIX 137 constraints (used here) as implemented in the Shelxtl software (Sheldrick, 2008).
Treatment of 2,2-disubstituted t-butyl beta-keto β-keto acids, which were used to probe the nature of the transition state for the thermal decarboxylation of β-keto acids (Logue et al., 1975). Structurally similar indanone-derived β-keto ester derivatives have been prepared recently (Mouri et al., 2009; Noritake et al., 2008; Rigby & Dixon, 2008). The directing nature of weak C—H···O H-bonds has been noted to be of importance to afford the three dimensional structure observed in these kinds of molecules (Karle et al., 2009).
with trifluoroacetic acid at room temperature quantitatively generates the corresponding 2,2-disubstitutedIn this contribution we present the solid state structure of one such 2,2-disubstituted β-keto acid, i.e. the title compound being the tolyl derivative. This is the second paper in a series of four dealing with substituted derivatives (H–, CH3– (this paper), Cl- and NO2– on the para-position of the phenyl ring) of the title compound. A more detailed comparison of all four substitution compounds will be given in the fourth paper of this series (Crosse et al., 2010a).
The molecule, Fig. 1, displays a bent geometry with a dihedral angle between the phenyl ring and a plane composed of the ester functionality of 75.3 (1)°. Molecules are linked by C—H···O weak hydrogen bonds generating infinite chains parallel to the b axis as shown in Fig. 2. The aromatic rings are not involved in intercalation of stacking interactions either within or between the chains. The chains are arranged with neighbouring t-butyl and dimethyl groups on adjacent chains exhibiting hydrophobic stacking with short C—H···H—C contacts between adjacent chains, Fig. 2 (Alkorta et al., 2008).
For the synthesis, spectroscopic characterization and reactivity of the title compound, see: Logue (1974); Logue et al. (1975). For related structures, see: Crosse et al. (2010a,b; Logue et al. (2010). For the syntheses and characterization of structurally similar indanone-derived β-keto ester derivatives, see: Mouri et al. (2009); Noritake et al. (2008); Rigby & Dixon (2008). For weak hydrogen-bonded interactions, see: Karle et al. (2009). For H···H interactions, see: Alkorta et al. (2008). Paper is 2nd in series (ZL2265, ZL2266, ZL2267, ZL2264)
Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994); cell
CAD-4 EXPRESS (Enraf–Nonius, 1994); data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SIR2004 (Burla et al., 2005); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and Mercury (Macrae et al., 2008); software used to prepare material for publication: WinGX (Farrugia, 1999) and publCIF (Westrip, 2010).C16H22O3 | F(000) = 1136 |
Mr = 262.34 | Dx = 1.108 Mg m−3 |
Orthorhombic, Pbca | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ac 2ab | Cell parameters from 25 reflections |
a = 8.605 (3) Å | θ = 10–15° |
b = 11.659 (3) Å | µ = 0.08 mm−1 |
c = 31.347 (9) Å | T = 291 K |
V = 3144.9 (16) Å3 | Prism, colourless |
Z = 8 | 0.50 × 0.30 × 0.10 mm |
Enraf–Nonius TurboCAD-4 diffractometer | 1334 reflections with I > 2σ(I) |
Radiation source: Enraf Nonius FR590 | Rint = 0.027 |
Graphite monochromator | θmax = 25.0°, θmin = 1.3° |
non–profiled ω scans | h = 0→10 |
Absorption correction: ψ scan (North et al., 1968) | k = 0→13 |
Tmin = 0.969, Tmax = 0.988 | l = −33→37 |
4411 measured reflections | 3 standard reflections every 166 min |
2758 independent reflections | intensity decay: 2% |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.049 | H-atom parameters constrained |
wR(F2) = 0.134 | w = 1/[σ2(Fo2) + (0.0573P)2 + 0.2581P] where P = (Fo2 + 2Fc2)/3 |
S = 1.01 | (Δ/σ)max < 0.001 |
2758 reflections | Δρmax = 0.14 e Å−3 |
178 parameters | Δρmin = −0.13 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 2008) |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0033 (5) |
C16H22O3 | V = 3144.9 (16) Å3 |
Mr = 262.34 | Z = 8 |
Orthorhombic, Pbca | Mo Kα radiation |
a = 8.605 (3) Å | µ = 0.08 mm−1 |
b = 11.659 (3) Å | T = 291 K |
c = 31.347 (9) Å | 0.50 × 0.30 × 0.10 mm |
Enraf–Nonius TurboCAD-4 diffractometer | 1334 reflections with I > 2σ(I) |
Absorption correction: ψ scan (North et al., 1968) | Rint = 0.027 |
Tmin = 0.969, Tmax = 0.988 | 3 standard reflections every 166 min |
4411 measured reflections | intensity decay: 2% |
2758 independent reflections |
R[F2 > 2σ(F2)] = 0.049 | 0 restraints |
wR(F2) = 0.134 | H-atom parameters constrained |
S = 1.01 | Δρmax = 0.14 e Å−3 |
2758 reflections | Δρmin = −0.13 e Å−3 |
178 parameters |
Experimental. Number of psi-scan sets used was 6. Theta correction was applied. Averaged transmission function was used. No Fourier smoothing was applied. |
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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. |
x | y | z | Uiso*/Ueq | ||
C1 | 0.6338 (3) | 0.2128 (2) | 0.65195 (7) | 0.0474 (6) | |
C2 | 0.7278 (3) | 0.3098 (2) | 0.65125 (7) | 0.0558 (7) | |
H2 | 0.7806 | 0.3292 | 0.6264 | 0.067* | |
C3 | 0.7434 (3) | 0.3773 (2) | 0.68702 (8) | 0.0647 (8) | |
H3 | 0.8068 | 0.4417 | 0.6857 | 0.078* | |
C4 | 0.6681 (4) | 0.3524 (3) | 0.72464 (9) | 0.0701 (8) | |
C5 | 0.5731 (4) | 0.2569 (3) | 0.72513 (9) | 0.0789 (9) | |
H5 | 0.5193 | 0.2385 | 0.7499 | 0.095* | |
C6 | 0.5566 (3) | 0.1886 (2) | 0.68967 (8) | 0.0655 (8) | |
H6 | 0.4922 | 0.1247 | 0.691 | 0.079* | |
C7 | 0.6872 (5) | 0.4275 (3) | 0.76352 (9) | 0.1102 (13) | |
H7A | 0.5982 | 0.419 | 0.7817 | 0.165* | |
H7B | 0.6963 | 0.5062 | 0.7548 | 0.165* | |
H7C | 0.7791 | 0.4052 | 0.7787 | 0.165* | |
C8 | 0.6120 (3) | 0.1326 (2) | 0.61524 (8) | 0.0517 (7) | |
O9 | 0.5392 (2) | 0.04387 (16) | 0.62062 (6) | 0.0725 (6) | |
C10 | 0.6724 (3) | 0.1633 (2) | 0.57086 (8) | 0.0527 (7) | |
C11 | 0.5841 (3) | 0.2689 (2) | 0.55401 (8) | 0.0724 (9) | |
H111 | 0.5999 | 0.3323 | 0.573 | 0.109* | |
H112 | 0.4752 | 0.2516 | 0.5524 | 0.109* | |
H113 | 0.6221 | 0.2884 | 0.5262 | 0.109* | |
O12 | 0.9115 (2) | 0.25100 (18) | 0.54691 (6) | 0.0790 (6) | |
O13 | 0.91700 (19) | 0.11790 (14) | 0.59947 (5) | 0.0560 (5) | |
C14 | 0.6468 (4) | 0.0623 (3) | 0.54016 (8) | 0.0826 (9) | |
H14A | 0.6857 | 0.082 | 0.5124 | 0.124* | |
H14B | 0.5378 | 0.0456 | 0.5383 | 0.124* | |
H14C | 0.701 | −0.004 | 0.5506 | 0.124* | |
C15 | 0.8467 (3) | 0.1858 (2) | 0.57099 (8) | 0.0557 (7) | |
C16 | 1.0892 (3) | 0.1174 (2) | 0.60458 (8) | 0.0608 (7) | |
C17 | 1.1112 (4) | 0.0345 (3) | 0.64115 (10) | 0.1023 (12) | |
H17A | 1.0663 | −0.0383 | 0.6338 | 0.153* | |
H17B | 1.0611 | 0.0641 | 0.6662 | 0.153* | |
H17C | 1.2202 | 0.0249 | 0.6467 | 0.153* | |
C18 | 1.1633 (4) | 0.0715 (3) | 0.56456 (10) | 0.0879 (10) | |
H181 | 1.2716 | 0.0574 | 0.5697 | 0.132* | |
H182 | 1.1522 | 0.1266 | 0.542 | 0.132* | |
H183 | 1.1132 | 0.0011 | 0.5565 | 0.132* | |
C19 | 1.1454 (4) | 0.2360 (3) | 0.61636 (11) | 0.0997 (11) | |
H19A | 1.0827 | 0.2658 | 0.6392 | 0.15* | |
H19B | 1.1372 | 0.2856 | 0.592 | 0.15* | |
H19C | 1.2518 | 0.2321 | 0.6254 | 0.15* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0430 (15) | 0.0492 (15) | 0.0498 (14) | 0.0041 (13) | 0.0019 (12) | 0.0026 (12) |
C2 | 0.0596 (18) | 0.0602 (16) | 0.0476 (14) | −0.0026 (15) | 0.0060 (14) | 0.0001 (13) |
C3 | 0.0670 (19) | 0.0641 (17) | 0.0630 (16) | −0.0065 (16) | −0.0012 (17) | −0.0118 (14) |
C4 | 0.076 (2) | 0.077 (2) | 0.0570 (18) | 0.0119 (18) | −0.0004 (16) | −0.0141 (16) |
C5 | 0.093 (2) | 0.091 (2) | 0.0528 (16) | 0.003 (2) | 0.0254 (17) | −0.0023 (17) |
C6 | 0.0686 (19) | 0.0664 (18) | 0.0615 (17) | −0.0029 (16) | 0.0132 (15) | 0.0052 (15) |
C7 | 0.130 (3) | 0.124 (3) | 0.077 (2) | 0.007 (3) | 0.006 (2) | −0.043 (2) |
C8 | 0.0408 (17) | 0.0548 (16) | 0.0596 (16) | 0.0055 (14) | −0.0066 (12) | 0.0018 (14) |
O9 | 0.0761 (15) | 0.0639 (12) | 0.0774 (12) | −0.0182 (11) | −0.0017 (11) | −0.0012 (10) |
C10 | 0.0520 (17) | 0.0610 (17) | 0.0451 (14) | 0.0039 (14) | −0.0048 (13) | −0.0042 (13) |
C11 | 0.069 (2) | 0.088 (2) | 0.0601 (17) | 0.0141 (17) | −0.0107 (15) | 0.0107 (15) |
O12 | 0.0748 (14) | 0.0883 (14) | 0.0741 (12) | 0.0026 (12) | 0.0128 (11) | 0.0238 (12) |
O13 | 0.0419 (11) | 0.0711 (12) | 0.0551 (10) | 0.0015 (9) | −0.0019 (9) | 0.0054 (9) |
C14 | 0.077 (2) | 0.096 (2) | 0.074 (2) | −0.0039 (19) | −0.0078 (16) | −0.0319 (17) |
C15 | 0.0585 (19) | 0.0615 (17) | 0.0471 (15) | 0.0036 (16) | 0.0019 (15) | −0.0046 (15) |
C16 | 0.0424 (17) | 0.0749 (19) | 0.0651 (17) | −0.0023 (15) | −0.0056 (13) | 0.0028 (15) |
C17 | 0.067 (2) | 0.139 (3) | 0.101 (2) | 0.002 (2) | −0.0184 (19) | 0.042 (2) |
C18 | 0.062 (2) | 0.113 (3) | 0.089 (2) | 0.013 (2) | 0.0140 (17) | −0.005 (2) |
C19 | 0.068 (2) | 0.103 (3) | 0.128 (3) | −0.013 (2) | −0.017 (2) | −0.022 (2) |
C1—C6 | 1.385 (3) | C11—H112 | 0.96 |
C1—C2 | 1.390 (3) | C11—H113 | 0.96 |
C1—C8 | 1.495 (3) | O12—C15 | 1.207 (3) |
C2—C3 | 1.376 (3) | O13—C15 | 1.338 (3) |
C2—H2 | 0.93 | O13—C16 | 1.491 (3) |
C3—C4 | 1.376 (4) | C14—H14A | 0.96 |
C3—H3 | 0.93 | C14—H14B | 0.96 |
C4—C5 | 1.382 (4) | C14—H14C | 0.96 |
C4—C7 | 1.509 (4) | C16—C18 | 1.505 (4) |
C5—C6 | 1.375 (4) | C16—C19 | 1.511 (4) |
C5—H5 | 0.93 | C16—C17 | 1.511 (4) |
C6—H6 | 0.93 | C17—H17A | 0.96 |
C7—H7A | 0.96 | C17—H17B | 0.96 |
C7—H7B | 0.96 | C17—H17C | 0.96 |
C7—H7C | 0.96 | C18—H181 | 0.96 |
C8—O9 | 1.221 (3) | C18—H182 | 0.96 |
C8—C10 | 1.528 (3) | C18—H183 | 0.96 |
C10—C15 | 1.523 (4) | C19—H19A | 0.96 |
C10—C14 | 1.537 (3) | C19—H19B | 0.96 |
C10—C11 | 1.540 (3) | C19—H19C | 0.96 |
C11—H111 | 0.96 | ||
C6—C1—C2 | 117.3 (2) | H111—C11—H113 | 109.5 |
C6—C1—C8 | 118.0 (2) | H112—C11—H113 | 109.5 |
C2—C1—C8 | 124.7 (2) | C15—O13—C16 | 121.6 (2) |
C3—C2—C1 | 120.6 (2) | C10—C14—H14A | 109.5 |
C3—C2—H2 | 119.7 | C10—C14—H14B | 109.5 |
C1—C2—H2 | 119.7 | H14A—C14—H14B | 109.5 |
C4—C3—C2 | 122.2 (3) | C10—C14—H14C | 109.5 |
C4—C3—H3 | 118.9 | H14A—C14—H14C | 109.5 |
C2—C3—H3 | 118.9 | H14B—C14—H14C | 109.5 |
C3—C4—C5 | 117.2 (3) | O12—C15—O13 | 125.5 (3) |
C3—C4—C7 | 121.2 (3) | O12—C15—C10 | 124.2 (3) |
C5—C4—C7 | 121.5 (3) | O13—C15—C10 | 110.2 (2) |
C6—C5—C4 | 121.3 (3) | O13—C16—C18 | 109.4 (2) |
C6—C5—H5 | 119.4 | O13—C16—C19 | 109.9 (2) |
C4—C5—H5 | 119.4 | C18—C16—C19 | 113.2 (3) |
C5—C6—C1 | 121.5 (3) | O13—C16—C17 | 102.0 (2) |
C5—C6—H6 | 119.3 | C18—C16—C17 | 110.6 (3) |
C1—C6—H6 | 119.3 | C19—C16—C17 | 111.1 (3) |
C4—C7—H7A | 109.5 | C16—C17—H17A | 109.5 |
C4—C7—H7B | 109.5 | C16—C17—H17B | 109.5 |
H7A—C7—H7B | 109.5 | H17A—C17—H17B | 109.5 |
C4—C7—H7C | 109.5 | C16—C17—H17C | 109.5 |
H7A—C7—H7C | 109.5 | H17A—C17—H17C | 109.5 |
H7B—C7—H7C | 109.5 | H17B—C17—H17C | 109.5 |
O9—C8—C1 | 119.2 (2) | C16—C18—H181 | 109.5 |
O9—C8—C10 | 119.9 (2) | C16—C18—H182 | 109.5 |
C1—C8—C10 | 120.8 (2) | H181—C18—H182 | 109.5 |
C15—C10—C8 | 111.9 (2) | C16—C18—H183 | 109.5 |
C15—C10—C14 | 106.0 (2) | H181—C18—H183 | 109.5 |
C8—C10—C14 | 110.0 (2) | H182—C18—H183 | 109.5 |
C15—C10—C11 | 110.4 (2) | C16—C19—H19A | 109.5 |
C8—C10—C11 | 109.4 (2) | C16—C19—H19B | 109.5 |
C14—C10—C11 | 109.1 (2) | H19A—C19—H19B | 109.5 |
C10—C11—H111 | 109.5 | C16—C19—H19C | 109.5 |
C10—C11—H112 | 109.5 | H19A—C19—H19C | 109.5 |
H111—C11—H112 | 109.5 | H19B—C19—H19C | 109.5 |
C10—C11—H113 | 109.5 |
D—H···A | D—H | H···A | D···A | D—H···A |
C3—H3···O9i | 0.93 | 2.71 | 3.407 (3) | 133 |
Symmetry code: (i) −x+3/2, y+1/2, z. |
Experimental details
Crystal data | |
Chemical formula | C16H22O3 |
Mr | 262.34 |
Crystal system, space group | Orthorhombic, Pbca |
Temperature (K) | 291 |
a, b, c (Å) | 8.605 (3), 11.659 (3), 31.347 (9) |
V (Å3) | 3144.9 (16) |
Z | 8 |
Radiation type | Mo Kα |
µ (mm−1) | 0.08 |
Crystal size (mm) | 0.50 × 0.30 × 0.10 |
Data collection | |
Diffractometer | Enraf–Nonius TurboCAD-4 |
Absorption correction | ψ scan (North et al., 1968) |
Tmin, Tmax | 0.969, 0.988 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 4411, 2758, 1334 |
Rint | 0.027 |
(sin θ/λ)max (Å−1) | 0.594 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.049, 0.134, 1.01 |
No. of reflections | 2758 |
No. of parameters | 178 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.14, −0.13 |
Computer programs: CAD-4 EXPRESS (Enraf–Nonius, 1994), XCAD4 (Harms & Wocadlo, 1995), SIR2004 (Burla et al., 2005), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 1997) and Mercury (Macrae et al., 2008), WinGX (Farrugia, 1999) and publCIF (Westrip, 2010).
D—H···A | D—H | H···A | D···A | D—H···A |
C3—H3···O9i | 0.93 | 2.71 | 3.407 (3) | 132.5 |
Symmetry code: (i) −x+3/2, y+1/2, z. |
Acknowledgements
Financial assistance from the Chemistry Department of Michigan Technological University is acknowledged.
References
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Treatment of 2,2-disubstituted t-butyl beta-keto esters with trifluoroacetic acid at room temperature quantitatively generates the corresponding 2,2-disubstituted β-keto acids, which were used to probe the nature of the transition state for the thermal decarboxylation of β-keto acids (Logue et al., 1975). Structurally similar indanone-derived β-keto ester derivatives have been prepared recently (Mouri et al., 2009; Noritake et al., 2008; Rigby & Dixon, 2008). The directing nature of weak C—H···O H-bonds has been noted to be of importance to afford the three dimensional structure observed in these kinds of molecules (Karle et al., 2009).
In this contribution we present the solid state structure of one such 2,2-disubstituted β-keto acid, i.e. the title compound being the tolyl derivative. This is the second paper in a series of four dealing with substituted derivatives (H–, CH3– (this paper), Cl- and NO2– on the para-position of the phenyl ring) of the title compound. A more detailed comparison of all four substitution compounds will be given in the fourth paper of this series (Crosse et al., 2010a).
The molecule, Fig. 1, displays a bent geometry with a dihedral angle between the phenyl ring and a plane composed of the ester functionality of 75.3 (1)°. Molecules are linked by C—H···O weak hydrogen bonds generating infinite chains parallel to the b axis as shown in Fig. 2. The aromatic rings are not involved in intercalation of stacking interactions either within or between the chains. The chains are arranged with neighbouring t-butyl and dimethyl groups on adjacent chains exhibiting hydrophobic stacking with short C—H···H—C contacts between adjacent chains, Fig. 2 (Alkorta et al., 2008).