r-2,c-6-Bis(4-chloro­phenyl)-t-3,t-5-di­methyl­tetra­hydro­pyran-4-one

The molecular structure of the title compound, C₁₉H₁₈Cl₂O₂, reveals a distorted chair conformation for the pyran ring, in which the methyl and 4-chloro­phenyl groups occupy equatorial positions. The mol­ecule is devoid of strong intramolec­ular interactions. In the crystal structure, the mol­ecules form zigzag layers which are held together by C—H...π interactions.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.051
• wR factor = 0.140
• Data-to-parameter ratio = 15.2

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

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S1. Comment

The title molecule, (I), contains two pairs of chiral C atoms with identical groups on each. There can be as many as four racemic modifications and two meso forms for the molecule (Eliel, 1962). This investigation was undertaken to assign the configuration and conformation of the most stable form in the solid state.

The saturated pyran ring adopts a distorted chair conformation, as shown by the torsion angles around the bonds involving the ring atoms. These torsion angles deviate from the ideal value of 56° reported for the chair conformation of cyclohexane (Kalsi, 1997). The C—C bond lengths of the phenyl rings are in the range 1.362 (4)–1.391 (4) Å, while the bond angles are in the range 118.3 (3)–121.4 (4)°. The configurations of the chiral atoms C2, C3, C5 and C6 are found to be R, S, R and S, respectively. The equatorial dispositions of the methyl and 4-chlorophenyl groups are revealed by the torsion angles comprising the external atom and the other three ring atoms, which vary from −167.9 (2) to 178.3 (2)°, as observed in a pentasubstituted cyclohexan-1-one derivative (Sarangarajan et al., 2002).

In the crystal structure, the molecules are aggregated into zigzag layers extended over the ac plane. Within the layer, a Cl···Cl short contact of 3.406 (2) Å is observed between atoms Cl1 and Cl2ⁱ [symmetry code: (i) −1/2 − x, −y, −1/2 + z]. The adjacent layers are linked through C—H···π interactions, viz. C3—H3···Cg, with H3···Cg = 2.72 Å, C3···Cg = 3.631 (3) Å and C3—H3···Cg = 154°, where Cg denotes the centroid of the C16—C21 phenyl ring of the molecule at (-x, 1/2 + y, 1/2 − z). The molecules are also held by weak interactions (Jeffrey & Senger, 1991) between C20 and O8ⁱⁱ [3.373 (4) Å; symmetry code: (ii) x − 1/2, y, −z + 1/2].

The title compound is isomorphous with the analogous p-tolyl derivative, r-2,c-6-di(p-tolyl)-t-3,t-5-dimethyltetrahydropyran-4-one (Krishnamoorthy et al., 2003), with very similar crystal and molecular structures. The torsion angles around the C—C bonds of the tetrahydropyran ring are not statistically different in the two structures. This reveals no conformational changes due to the replacement of methyl by Cl atoms in the title molecule. The gas-phase conformation obtained through AM1 calculations is very similar to that observed in the solid state. The calculated heat of formation of −48.5 kcal mol⁻¹ for the compound reveals its inherent molecular stability.

S2. Experimental

The title compound was prepared by the condensation of pentan-3-one and 4-chlorobenzaldehyde in a 1:2 molar ratio in methanol, as reported by Baliah & Mangalam (1978). Diffraction-quality crystals were obtained by recrystallization of the crude product from ethanol.

Computing details

Data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: CAD-4 Software; data reduction: MolEN (Fair, 1990); program(s) used to solve structure: SIR92 (Altomare et al., 1993); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and PLATON (Spek, 1997); software used to prepare material for publication: SHELXL97 and PARST (Nardelli, 1983).

Figures

	Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids.
	Fig. 2. A view of the molecular packing, showing the zigzag layer formation.

r-2,c-6-di(4-chlorophenyl)-t-3,t-5-dimethyltetrahydropyran-4-one

Crystal data

C19H18Cl2O2	Dx = 1.330 Mg m^−3
Mr = 349.23	Melting point: 463-464 K K
Orthorhombic, Pbca	Mo Kα radiation, λ = 0.71069 Å
Hall symbol: -P 2ac 2ab	Cell parameters from 25 reflections
a = 15.013 (1) Å	θ = 2–12°
b = 9.1230 (16) Å	µ = 0.38 mm^−1
c = 25.462 (4) Å	T = 293 K
V = 3487.4 (9) Å^3	Plate, colourless
Z = 8	0.20 × 0.15 × 0.10 mm
F(000) = 1456

Data collection

Enraf-Nonius CAD-4 diffractometer	2205 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.041
Graphite monochromator	θmax = 25.3°, θmin = 1.6°
ω–2θ scans	h = −18→0
Absorption correction: ψ scan (North et al., 1968)	k = 0→10
Tmin = 0.934, Tmax = 0.963	l = 0→30
3164 measured reflections	3 standard reflections every 100 reflections
3163 independent reflections	intensity decay: none

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)] = 0.051	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.140	H-atom parameters constrained
S = 1.10	w = 1/[σ^2(Fo^2) + (0.0478P)^2 + 2.3284P] where P = (Fo^2 + 2Fc^2)/3
3163 reflections	(Δ/σ)max < 0.001
208 parameters	Δρmax = 0.22 e Å^−3
0 restraints	Δρmin = −0.34 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. The hydrogen atoms were included in the calculated positions. The thermal parameters of all the H atoms were fixed as 1.2 times of the U_eq of their carrier atoms, except those of the methyl groups. The thermal parameters of the H atoms were fixed as 1.5 times of the U_eq of the respective carbon atoms.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Cl1	−0.23836 (7)	0.02833 (16)	0.01666 (4)	0.0972 (4)
Cl2	−0.08127 (7)	0.15480 (12)	0.46889 (3)	0.0824 (3)
O1	0.02534 (12)	0.1605 (2)	0.21639 (7)	0.0458 (5)
O8	0.24462 (15)	0.3915 (3)	0.18791 (9)	0.0769 (7)
C2	0.06250 (18)	0.1593 (3)	0.16462 (10)	0.0443 (7)
H2	0.1069	0.0808	0.1622	0.053*
C3	0.10719 (19)	0.3064 (3)	0.15152 (11)	0.0503 (7)
H3	0.0599	0.3802	0.1494	0.060*
C4	0.16895 (19)	0.3520 (4)	0.19549 (11)	0.0512 (7)
C5	0.12892 (19)	0.3420 (3)	0.24983 (11)	0.0473 (7)
H5	0.0795	0.4120	0.2516	0.057*
C6	0.08960 (18)	0.1865 (3)	0.25631 (10)	0.0437 (6)
H6	0.1376	0.1141	0.2533	0.052*
C7	0.1531 (2)	0.3028 (5)	0.09841 (12)	0.0757 (11)
H7A	0.1804	0.3961	0.0917	0.114*
H7B	0.1100	0.2823	0.0715	0.114*
H7C	0.1979	0.2277	0.0984	0.114*
C9	0.1958 (2)	0.3839 (5)	0.29223 (13)	0.0718 (10)
H9A	0.2177	0.4811	0.2857	0.108*
H9B	0.2446	0.3160	0.2918	0.108*
H9C	0.1673	0.3811	0.3260	0.108*
C10	−0.01328 (19)	0.1260 (3)	0.12766 (10)	0.0466 (7)
C11	−0.0038 (2)	0.0220 (4)	0.08873 (11)	0.0569 (8)
H11	0.0498	−0.0283	0.0853	0.068*
C12	−0.0732 (2)	−0.0083 (4)	0.05471 (12)	0.0654 (9)
H12	−0.0665	−0.0795	0.0289	0.079*
C13	−0.1515 (2)	0.0666 (4)	0.05918 (11)	0.0616 (9)
C14	−0.1623 (2)	0.1733 (4)	0.09694 (12)	0.0625 (9)
H14	−0.2154	0.2256	0.0993	0.075*
C15	−0.09288 (19)	0.2017 (4)	0.13140 (12)	0.0538 (8)
H15	−0.0999	0.2724	0.1574	0.065*
C16	0.04384 (18)	0.1679 (3)	0.30830 (10)	0.0424 (6)
C17	0.08966 (19)	0.1095 (4)	0.35091 (11)	0.0506 (7)
H17	0.1473	0.0745	0.3462	0.061*
C18	0.0508 (2)	0.1028 (4)	0.40025 (11)	0.0557 (8)
H18	0.0822	0.0648	0.4286	0.067*
C19	−0.0341 (2)	0.1526 (3)	0.40650 (11)	0.0547 (8)
C20	−0.0826 (2)	0.2061 (4)	0.36463 (12)	0.0562 (8)
H20	−0.1412	0.2365	0.3692	0.067*
C21	−0.04284 (18)	0.2138 (3)	0.31581 (11)	0.0496 (7)
H21	−0.0750	0.2505	0.2875	0.060*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.0773 (6)	0.1501 (11)	0.0640 (5)	−0.0286 (7)	−0.0242 (5)	−0.0028 (6)
Cl2	0.0999 (7)	0.0936 (8)	0.0537 (5)	−0.0075 (6)	0.0291 (5)	0.0007 (5)
O1	0.0458 (10)	0.0551 (13)	0.0366 (9)	−0.0067 (9)	−0.0020 (8)	0.0008 (9)
O8	0.0471 (12)	0.110 (2)	0.0735 (15)	−0.0191 (13)	0.0107 (12)	−0.0026 (15)
C2	0.0494 (15)	0.0456 (17)	0.0378 (14)	0.0046 (13)	0.0006 (12)	0.0016 (12)
C3	0.0470 (16)	0.0554 (19)	0.0486 (16)	0.0008 (14)	0.0038 (13)	0.0078 (14)
C4	0.0425 (16)	0.0537 (19)	0.0573 (17)	0.0019 (14)	0.0035 (13)	0.0002 (15)
C5	0.0441 (15)	0.0467 (17)	0.0512 (15)	−0.0031 (13)	0.0008 (12)	−0.0039 (14)
C6	0.0431 (14)	0.0463 (17)	0.0415 (14)	0.0024 (13)	−0.0034 (12)	−0.0003 (12)
C7	0.069 (2)	0.110 (3)	0.0489 (18)	−0.014 (2)	0.0109 (16)	0.0066 (19)
C9	0.072 (2)	0.082 (3)	0.062 (2)	−0.026 (2)	−0.0054 (17)	−0.0058 (19)
C10	0.0523 (16)	0.0500 (18)	0.0376 (13)	−0.0012 (14)	−0.0009 (12)	0.0025 (13)
C11	0.0662 (19)	0.056 (2)	0.0482 (15)	0.0066 (16)	−0.0012 (14)	−0.0047 (15)
C12	0.082 (2)	0.072 (2)	0.0428 (16)	−0.004 (2)	−0.0047 (16)	−0.0096 (16)
C13	0.063 (2)	0.081 (3)	0.0409 (16)	−0.0159 (18)	−0.0075 (14)	0.0064 (16)
C14	0.0485 (17)	0.080 (3)	0.0592 (19)	0.0001 (17)	−0.0002 (15)	0.0048 (18)
C15	0.0487 (16)	0.060 (2)	0.0522 (17)	0.0036 (15)	0.0000 (13)	−0.0061 (15)
C16	0.0445 (15)	0.0420 (16)	0.0407 (14)	−0.0025 (12)	−0.0015 (11)	−0.0026 (12)
C17	0.0483 (16)	0.0571 (19)	0.0463 (15)	0.0041 (14)	−0.0033 (13)	0.0001 (14)
C18	0.0640 (19)	0.059 (2)	0.0439 (16)	0.0009 (16)	−0.0019 (14)	0.0039 (14)
C19	0.0618 (19)	0.054 (2)	0.0484 (16)	−0.0069 (16)	0.0095 (14)	−0.0044 (15)
C20	0.0461 (16)	0.063 (2)	0.0591 (18)	0.0013 (15)	0.0069 (14)	−0.0057 (16)
C21	0.0467 (15)	0.0556 (19)	0.0466 (15)	0.0041 (14)	−0.0021 (13)	0.0018 (14)

Geometric parameters (Å, º)

Cl1—C13	1.731 (3)	C9—H9C	0.96
Cl2—C19	1.740 (3)	C10—C11	1.380 (4)
O1—C6	1.421 (3)	C10—C15	1.383 (4)
O1—C2	1.431 (3)	C11—C12	1.383 (4)
O8—C4	1.207 (3)	C11—H11	0.93
C2—C10	1.507 (4)	C12—C13	1.364 (5)
C2—C3	1.537 (4)	C12—H12	0.93
C2—H2	0.98	C13—C14	1.378 (5)
C3—C4	1.512 (4)	C14—C15	1.387 (4)
C3—C7	1.518 (4)	C14—H14	0.93
C3—H3	0.98	C15—H15	0.93
C4—C5	1.511 (4)	C16—C21	1.380 (4)
C5—C9	1.523 (4)	C16—C17	1.391 (4)
C5—C6	1.546 (4)	C17—C18	1.387 (4)
C5—H5	0.98	C17—H17	0.93
C6—C16	1.501 (4)	C18—C19	1.362 (4)
C6—H6	0.98	C18—H18	0.93
C7—H7A	0.96	C19—C20	1.381 (4)
C7—H7B	0.96	C20—C21	1.381 (4)
C7—H7C	0.96	C20—H20	0.93
C9—H9A	0.96	C21—H21	0.93
C9—H9B	0.96
C6—O1—C2	113.28 (19)	H9A—C9—H9C	109.5
O1—C2—C10	106.4 (2)	H9B—C9—H9C	109.5
O1—C2—C3	111.3 (2)	C11—C10—C15	118.8 (3)
C10—C2—C3	111.7 (2)	C11—C10—C2	120.6 (3)
O1—C2—H2	109.1	C15—C10—C2	120.6 (3)
C10—C2—H2	109.1	C10—C11—C12	120.6 (3)
C3—C2—H2	109.1	C10—C11—H11	119.7
C4—C3—C7	112.8 (2)	C12—C11—H11	119.7
C4—C3—C2	110.3 (2)	C13—C12—C11	119.8 (3)
C7—C3—C2	111.9 (3)	C13—C12—H12	120.1
C4—C3—H3	107.2	C11—C12—H12	120.1
C7—C3—H3	107.2	C12—C13—C14	120.9 (3)
C2—C3—H3	107.2	C12—C13—Cl1	119.7 (3)
O8—C4—C5	122.6 (3)	C14—C13—Cl1	119.4 (3)
O8—C4—C3	122.7 (3)	C13—C14—C15	119.0 (3)
C5—C4—C3	114.7 (2)	C13—C14—H14	120.5
C4—C5—C9	111.8 (2)	C15—C14—H14	120.5
C4—C5—C6	107.7 (2)	C10—C15—C14	120.9 (3)
C9—C5—C6	114.0 (3)	C10—C15—H15	119.6
C4—C5—H5	107.7	C14—C15—H15	119.6
C9—C5—H5	107.7	C21—C16—C17	118.3 (3)
C6—C5—H5	107.7	C21—C16—C6	121.3 (2)
O1—C6—C16	107.5 (2)	C17—C16—C6	120.3 (2)
O1—C6—C5	109.6 (2)	C18—C17—C16	121.0 (3)
C16—C6—C5	111.9 (2)	C18—C17—H17	119.5
O1—C6—H6	109.2	C16—C17—H17	119.5
C16—C6—H6	109.2	C19—C18—C17	119.0 (3)
C5—C6—H6	109.2	C19—C18—H18	120.5
C3—C7—H7A	109.5	C17—C18—H18	120.5
C3—C7—H7B	109.5	C18—C19—C20	121.4 (3)
H7A—C7—H7B	109.5	C18—C19—Cl2	119.5 (2)
C3—C7—H7C	109.5	C20—C19—Cl2	119.1 (2)
H7A—C7—H7C	109.5	C21—C20—C19	119.0 (3)
H7B—C7—H7C	109.5	C21—C20—H20	120.5
C5—C9—H9A	109.5	C19—C20—H20	120.5
C5—C9—H9B	109.5	C16—C21—C20	121.1 (3)
H9A—C9—H9B	109.5	C16—C21—H21	119.4
C5—C9—H9C	109.5	C20—C21—H21	119.4
C6—O1—C2—C10	178.3 (2)	C15—C10—C11—C12	−1.3 (5)
C6—O1—C2—C3	−59.8 (3)	C2—C10—C11—C12	−179.8 (3)
O1—C2—C3—C4	49.2 (3)	C10—C11—C12—C13	0.8 (5)
C10—C2—C3—C4	167.9 (2)	C11—C12—C13—C14	0.6 (5)
O1—C2—C3—C7	175.6 (2)	C11—C12—C13—Cl1	−179.9 (3)
C10—C2—C3—C7	−65.6 (3)	C12—C13—C14—C15	−1.5 (5)
C7—C3—C4—O8	5.1 (5)	Cl1—C13—C14—C15	179.0 (2)
C2—C3—C4—O8	131.1 (3)	C11—C10—C15—C14	0.3 (5)
C7—C3—C4—C5	−174.0 (3)	C2—C10—C15—C14	178.9 (3)
C2—C3—C4—C5	−48.0 (3)	C13—C14—C15—C10	1.0 (5)
O8—C4—C5—C9	−1.3 (4)	O1—C6—C16—C21	−37.5 (3)
C3—C4—C5—C9	177.8 (3)	C5—C6—C16—C21	83.0 (3)
O8—C4—C5—C6	−127.3 (3)	O1—C6—C16—C17	145.4 (3)
C3—C4—C5—C6	51.8 (3)	C5—C6—C16—C17	−94.1 (3)
C2—O1—C6—C16	−173.7 (2)	C21—C16—C17—C18	−2.5 (5)
C2—O1—C6—C5	64.5 (3)	C6—C16—C17—C18	174.6 (3)
C4—C5—C6—O1	−57.9 (3)	C16—C17—C18—C19	0.9 (5)
C9—C5—C6—O1	177.4 (2)	C17—C18—C19—C20	1.6 (5)
C4—C5—C6—C16	−177.1 (2)	C17—C18—C19—Cl2	−176.2 (2)
C9—C5—C6—C16	58.2 (3)	C18—C19—C20—C21	−2.3 (5)
O1—C2—C10—C11	−133.0 (3)	Cl2—C19—C20—C21	175.5 (2)
C3—C2—C10—C11	105.3 (3)	C17—C16—C21—C20	1.8 (4)
O1—C2—C10—C15	48.5 (4)	C6—C16—C21—C20	−175.3 (3)
C3—C2—C10—C15	−73.2 (3)	C19—C20—C21—C16	0.6 (5)