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Acta Cryst. (2007). E63, o4075    [ doi:10.1107/S1600536807043619 ]

3-Triphenylmethyl-2,4-pentanedione

R. E. Sykora, K. Kalachnikova and G. T. Spyridis

Abstract top

The title compound, C24H22O2, exists exclusively as the keto tautomer in the crystalline state with a dihedral angle of 66.8 (2)° between the carbonyl groups. Furthermore, steric crowding produces an uncommonly long carbon-carbon bond [1.587 (3) Å] linking the triphenylmethyl and diketone moieties.

Comment top

Acetylacetone (2,4-pentanedione) and other β-diketones are molecules in dynamic equilibrium with both tautomers present in measurable concentrations at equilibrium. The keto-enol ratio in these systems is modulated by solvent polarity, hydrogen bonding capacity, and the concentration of dissolved salts (Pocker & Spyridis, 2002; Emsley, 1984). This ratio is also exquisitely sensitive to the size of the substituents on the carbon between the carbonyls, with the keto concentration increasing as the steric bulk rises (Emsley, 1984). In light of our recent investigations into the keto-enol ratio of acetylacetone in highly concentrated nonaqueous salt solutions (Pocker & Spyridis, 2002), we prepared and crystallized 3-triphenyl-2,4-pentanedione, 1.

The title compound exists exclusively in the diketo form with steric crowding producing an uncommonly long C3—C6 bond of 1.587 (3) Å. This is close to the adamantyl-diketone bond length of 1.595 (8) Å observed in 3-methyl-3-(1-adamantyl)-2,4-pentanedione, 2 (Moreno-Manas et al., 1992). The C2—C3 and C3—C4 linkages at 1.544 (3) and 1.531 (3) Å, respectively, are also slightly longer than the 1.50 Å typical for sp2-sp3 carbon-carbon bonds (Wiorkiewicz-Kuczera & Rabczenko, 1986), as are the phenyl-carbon bonds about C6. Steric congestion also produces bond angles about C3 that are unusually large for a sp3 hybridized carbon: C2—C3—C6 is 116.5 (2)° while C4—C3—C6 is 117.23 (19)°.

The main factor determining the conformation of the keto tautomer is the strong repulsion of the localized C═O bond dipoles (Emsley et al., 1986). For both 1 and 2 the C2—C3—C4 angle is between 105–107° while for the keto tautomer of acetylaceone (Lowery et al., 1971) the corresponding angle is 114°, possibly in an effort to minimize the interaction between the carbonyl bond dipoles. For β-diketones possessing large groups about C3 semiempirical MM2 calculations (Moreno-Manas et al., 1991) reveal that the conformations which predominate are those with a dihedral angle between the carbonyls of less than 90°, with their contribution increasing as the bulk of the substituent rises. For 1 only a single conformation is oberved in the crystalline state and it possesses a dihedral angle of 66.8 (2)° between the carbonyls.

Related literature top

For related literature, see: Emsley (1984); Emsley et al. (1986); Lowery et al. (1971); Moreno-Manas et al. (1991, 1992); Pocker & Spyridis (2002); Wiorkiewicz-Kuczera & Rabczenko (1986); Zaugg & Schaefer (1965).

Experimental top

The title compound was synthesized as outlined in the literature (Zaugg & Schaefer, 1965) and purified by column chromatography over silica gel using 1:1 n-pentane: n-hexane as the mobile phase. Crystals suitable for X-ray analysis were grown by slow evaporation from 1:1 n-pentane: n-hexane at 298 K. The crystals of 1 did not cleave very well and several attempts to break or cut them were unsuccessful. Therefore a larger than standard crystal (1 mm max. dimension) was used for this study. The beam tube that was used was large enough (2 mm i.d.) to ensure that the crystal was completely inside of the X-ray beam during the diffraction experiment.

Refinement top

H atoms were placed in calculated positions and allowed to ride during subsequent refinement, with Uiso(H) = 1.2Ueq(C) and C—H distances of 0.93 Å for H atoms attached to the aromatic rings, Uiso(H) = 1.5Ueq(C) and C—H distances of 0.96 Å for the methyl H atoms, and Uiso(H) = 1.2Ueq(C) and a C—H distance of 0.98 Å for the tertiary H atom.

Computing details top

Data collection: CAD-4-PC Software (Enraf–Nonius, 1993); cell refinement: CAD-4-PC Software (Enraf–Nonius, 1993); data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1998); software used to prepare material for publication: publCIF (Westrip, 2007).

Figures top
[Figure 1] Fig. 1. The molecular structure of 1, with the atom-numbering scheme. Displacement ellipsoids for non-hydrogen atoms are drawn at the 50% probability level. Hydrogen atoms are not shown for clarity.
3-Triphenylmethyl-2,4-pentanedione top
Crystal data top
C24H22O2F000 = 728
Mr = 342.42Dx = 1.225 Mg m−3
Monoclinic, P21/nMo Kα radiation
λ = 0.71073 Å
Hall symbol: -P 2ynCell parameters from 25 reflections
a = 9.1906 (11) Åθ = 8.1–13.5º
b = 23.704 (3) ŵ = 0.08 mm−1
c = 9.3251 (13) ÅT = 290 (2) K
β = 113.941 (12)ºPlate, colorless
V = 1856.7 (4) Å31.00 × 0.48 × 0.17 mm
Z = 4
Data collection top
Enraf–Nonius CAD-4
diffractometer		Rint = 0.043
Radiation source: fine-focus sealed tubeθmax = 25.4º
Monochromator: graphiteθmin = 2.5º
T = 290(2) Kh = 0→11
θ/2θ scansk = 0→28
Absorption correction: ψ scan
(North et al., 1968)		l = −11→10
Tmin = 0.868, Tmax = 0.9913 standard reflections
3594 measured reflections every 120 min
3378 independent reflections intensity decay: none
1775 reflections with I > 2σ(I)
Refinement top
Refinement on F2Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: fullH-atom parameters constrained
R[F2 > 2σ(F2)] = 0.047  w = 1/[σ2(Fo2) + (0.0688P)2]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.148(Δ/σ)max < 0.001
S = 0.99Δρmax = 0.19 e Å−3
3378 reflectionsΔρmin = −0.16 e Å−3
238 parametersExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.014 (2)
Secondary atom site location: difference Fourier map
Crystal data top
C24H22O2V = 1856.7 (4) Å3
Mr = 342.42Z = 4
Monoclinic, P21/nMo Kα
a = 9.1906 (11) ŵ = 0.08 mm−1
b = 23.704 (3) ÅT = 290 (2) K
c = 9.3251 (13) Å1.00 × 0.48 × 0.17 mm
β = 113.941 (12)º
Data collection top
Enraf–Nonius CAD-4
diffractometer		1775 reflections with I > 2σ(I)
Absorption correction: ψ scan
(North et al., 1968)		Rint = 0.043
Tmin = 0.868, Tmax = 0.9913 standard reflections
3594 measured reflections every 120 min
3378 independent reflections intensity decay: none
Refinement top
R[F2 > 2σ(F2)] = 0.047238 parameters
wR(F2) = 0.148H-atom parameters constrained
S = 0.99Δρmax = 0.19 e Å−3
3378 reflectionsΔρmin = −0.16 e Å−3
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 > 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
O10.9972 (2)0.23311 (8)0.6900 (2)0.0575 (5)
O20.9543 (3)0.27619 (8)0.3716 (2)0.0740 (7)
C10.7447 (4)0.27723 (14)0.5824 (4)0.0776 (10)
H1A0.78730.29950.67640.116*
H1B0.65270.25710.57860.116*
H1C0.71520.30150.49260.116*
C20.8678 (3)0.23625 (11)0.5817 (3)0.0472 (7)
C30.8210 (3)0.20020 (10)0.4317 (3)0.0382 (6)
H3A0.70510.20370.37740.046*
C40.8882 (3)0.23122 (11)0.3279 (3)0.0457 (7)
C50.8630 (3)0.20898 (12)0.1699 (3)0.0583 (8)
H5A0.94230.22440.13870.087*
H5B0.75910.21970.09520.087*
H5C0.87140.16860.17430.087*
C60.8549 (3)0.13449 (9)0.4564 (3)0.0349 (6)
C70.8657 (3)0.11838 (10)0.6212 (3)0.0377 (6)
C80.9936 (3)0.09073 (11)0.7339 (3)0.0496 (7)
H8A1.08160.08170.71320.060*
C90.9922 (4)0.07632 (13)0.8774 (3)0.0633 (8)
H9A1.07960.05800.95220.076*
C100.8635 (4)0.08876 (14)0.9098 (3)0.0665 (9)
H10A0.86320.07881.00620.080*
C110.7344 (4)0.11606 (14)0.7995 (3)0.0627 (8)
H11A0.64680.12480.82120.075*
C120.7357 (3)0.13033 (12)0.6568 (3)0.0504 (7)
H12A0.64750.14840.58240.060*
C130.7134 (3)0.09979 (10)0.3388 (3)0.0365 (6)
C140.6992 (3)0.04335 (11)0.3709 (3)0.0495 (7)
H14A0.77520.02760.46170.059*
C150.5764 (3)0.00993 (12)0.2726 (3)0.0585 (8)
H15A0.5708−0.02780.29730.070*
C160.4627 (3)0.03230 (13)0.1384 (3)0.0591 (8)
H16A0.37890.01000.07260.071*
C170.4733 (3)0.08740 (12)0.1020 (3)0.0556 (8)
H17A0.39750.10250.01000.067*
C180.5965 (3)0.12122 (11)0.2015 (3)0.0445 (6)
H18A0.60090.15890.17570.053*
C191.0120 (3)0.11948 (10)0.4404 (3)0.0361 (6)
C201.1484 (3)0.15112 (11)0.5224 (3)0.0483 (7)
H20A1.14440.18020.58770.058*
C211.2892 (3)0.14001 (12)0.5082 (4)0.0568 (8)
H21A1.37930.16130.56510.068*
C221.2977 (3)0.09809 (12)0.4113 (3)0.0548 (7)
H22A1.39200.09150.39950.066*
C231.1649 (3)0.06562 (11)0.3315 (3)0.0493 (7)
H23A1.17010.03650.26700.059*
C241.0237 (3)0.07625 (10)0.3468 (3)0.0421 (6)
H24A0.93520.05380.29290.051*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0433 (11)0.0637 (12)0.0543 (12)−0.0069 (9)0.0082 (10)−0.0163 (9)
O20.0818 (15)0.0550 (13)0.0785 (15)−0.0209 (11)0.0257 (12)0.0060 (11)
C10.0573 (19)0.078 (2)0.092 (2)0.0045 (16)0.0250 (18)−0.0377 (19)
C20.0375 (15)0.0458 (15)0.0561 (17)−0.0059 (12)0.0168 (14)−0.0075 (13)
C30.0280 (12)0.0394 (13)0.0420 (13)−0.0005 (10)0.0088 (11)−0.0024 (11)
C40.0377 (14)0.0385 (14)0.0538 (17)0.0031 (12)0.0113 (12)0.0090 (12)
C50.0631 (19)0.0624 (17)0.0569 (17)0.0063 (15)0.0321 (15)0.0117 (15)
C60.0282 (12)0.0387 (13)0.0339 (13)0.0014 (10)0.0085 (10)0.0008 (10)
C70.0301 (13)0.0447 (14)0.0322 (13)−0.0042 (11)0.0063 (11)−0.0024 (11)
C80.0403 (15)0.0570 (17)0.0422 (15)0.0008 (13)0.0071 (12)0.0028 (13)
C90.0616 (19)0.076 (2)0.0379 (16)0.0029 (16)0.0055 (14)0.0109 (15)
C100.078 (2)0.085 (2)0.0332 (16)−0.0149 (18)0.0195 (16)−0.0009 (15)
C110.0549 (18)0.087 (2)0.0472 (17)−0.0075 (16)0.0221 (15)−0.0045 (16)
C120.0375 (14)0.0686 (19)0.0419 (16)−0.0021 (13)0.0129 (12)−0.0005 (13)
C130.0333 (13)0.0408 (14)0.0344 (13)−0.0011 (10)0.0126 (11)−0.0032 (11)
C140.0499 (16)0.0475 (16)0.0437 (15)−0.0022 (13)0.0112 (13)−0.0008 (13)
C150.0632 (19)0.0460 (16)0.0615 (18)−0.0150 (14)0.0202 (16)−0.0102 (14)
C160.0455 (17)0.0642 (19)0.0583 (19)−0.0119 (14)0.0114 (15)−0.0238 (15)
C170.0399 (15)0.0672 (19)0.0432 (16)−0.0009 (14)0.0000 (13)−0.0110 (14)
C180.0380 (14)0.0473 (15)0.0418 (14)0.0004 (11)0.0096 (12)−0.0014 (12)
C190.0303 (13)0.0383 (13)0.0374 (13)0.0041 (10)0.0112 (10)0.0051 (11)
C200.0358 (14)0.0486 (15)0.0583 (17)0.0003 (12)0.0167 (13)−0.0069 (13)
C210.0324 (15)0.0601 (18)0.074 (2)−0.0009 (13)0.0181 (14)−0.0084 (16)
C220.0381 (15)0.0669 (19)0.0624 (19)0.0089 (13)0.0235 (14)0.0030 (15)
C230.0503 (17)0.0562 (17)0.0440 (15)0.0122 (13)0.0219 (13)−0.0011 (13)
C240.0378 (14)0.0478 (15)0.0344 (13)0.0046 (11)0.0082 (11)0.0015 (11)
Geometric parameters (Å, °) top
O1—C21.211 (3)C11—C121.378 (4)
O2—C41.212 (3)C11—H11A0.9300
C1—C21.493 (4)C12—H12A0.9300
C1—H1A0.9600C13—C141.388 (3)
C1—H1B0.9600C13—C181.391 (3)
C1—H1C0.9600C14—C151.379 (3)
C2—C31.544 (3)C14—H14A0.9300
C3—C41.531 (3)C15—C161.370 (4)
C3—C61.587 (3)C15—H15A0.9300
C3—H3A0.9800C16—C171.363 (4)
C4—C51.492 (4)C16—H16A0.9300
C5—H5A0.9600C17—C181.390 (3)
C5—H5B0.9600C17—H17A0.9300
C5—H5C0.9600C18—H18A0.9300
C6—C71.547 (3)C19—C241.379 (3)
C6—C191.551 (3)C19—C201.393 (3)
C6—C131.554 (3)C20—C211.379 (3)
C7—C81.383 (3)C20—H20A0.9300
C7—C121.393 (3)C21—C221.366 (4)
C8—C91.386 (4)C21—H21A0.9300
C8—H8A0.9300C22—C231.378 (4)
C9—C101.366 (4)C22—H22A0.9300
C9—H9A0.9300C23—C241.385 (3)
C10—C111.376 (4)C23—H23A0.9300
C10—H10A0.9300C24—H24A0.9300
C2—C1—H1A109.5C10—C11—C12119.7 (3)
C2—C1—H1B109.5C10—C11—H11A120.2
H1A—C1—H1B109.5C12—C11—H11A120.2
C2—C1—H1C109.5C11—C12—C7121.6 (3)
H1A—C1—H1C109.5C11—C12—H12A119.2
H1B—C1—H1C109.5C7—C12—H12A119.2
O1—C2—C1121.7 (2)C14—C13—C18116.5 (2)
O1—C2—C3122.7 (2)C14—C13—C6118.9 (2)
C1—C2—C3115.6 (2)C18—C13—C6124.7 (2)
C4—C3—C2105.75 (19)C15—C14—C13122.2 (3)
C4—C3—C6117.23 (19)C15—C14—H14A118.9
C2—C3—C6116.5 (2)C13—C14—H14A118.9
C4—C3—H3A105.4C16—C15—C14120.0 (3)
C2—C3—H3A105.4C16—C15—H15A120.0
C6—C3—H3A105.4C14—C15—H15A120.0
O2—C4—C5119.9 (3)C17—C16—C15119.5 (3)
O2—C4—C3119.1 (2)C17—C16—H16A120.2
C5—C4—C3120.9 (2)C15—C16—H16A120.2
C4—C5—H5A109.5C16—C17—C18120.5 (3)
C4—C5—H5B109.5C16—C17—H17A119.7
H5A—C5—H5B109.5C18—C17—H17A119.7
C4—C5—H5C109.5C17—C18—C13121.3 (2)
H5A—C5—H5C109.5C17—C18—H18A119.4
H5B—C5—H5C109.5C13—C18—H18A119.4
C7—C6—C19110.60 (18)C24—C19—C20117.6 (2)
C7—C6—C13105.55 (18)C24—C19—C6123.1 (2)
C19—C6—C13110.85 (18)C20—C19—C6119.3 (2)
C7—C6—C3108.44 (18)C21—C20—C19121.0 (3)
C19—C6—C3110.29 (18)C21—C20—H20A119.5
C13—C6—C3111.00 (17)C19—C20—H20A119.5
C8—C7—C12117.5 (2)C22—C21—C20120.7 (3)
C8—C7—C6124.3 (2)C22—C21—H21A119.7
C12—C7—C6118.1 (2)C20—C21—H21A119.7
C7—C8—C9120.8 (3)C21—C22—C23119.2 (3)
C7—C8—H8A119.6C21—C22—H22A120.4
C9—C8—H8A119.6C23—C22—H22A120.4
C10—C9—C8120.5 (3)C22—C23—C24120.3 (3)
C10—C9—H9A119.7C22—C23—H23A119.9
C8—C9—H9A119.7C24—C23—H23A119.9
C9—C10—C11119.8 (3)C19—C24—C23121.2 (2)
C9—C10—H10A120.1C19—C24—H24A119.4
C11—C10—H10A120.1C23—C24—H24A119.4
Acknowledgements top

The authors gratefully acknowledge the Department of Energy and Oak Ridge National Laboratory for the loan of an Enraf–Nonius CAD-4 X-ray diffractometer.

references
References top

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