(E)-1,2-Bis(4-methyl­phen­yl)ethane-1,2-dione

Hoong-Kun Fun; Reza Kia

doi:10.1107/S1600536808023386

. 2008 Jul 31;64(Pt 8):o1615–o1616. doi: 10.1107/S1600536808023386

(E)-1,2-Bis(4-methylphenyl)ethane-1,2-dione

Hoong-Kun Fun ^a,^*, Reza Kia ^a,^‡

PMCID: PMC2962226 PMID: 21203307

Abstract

In the molecule of the title compound, C₁₆H₁₄O₂, a substituted benzil, the dicarbonyl unit has an s-trans conformation. This conformation is substantiated by the O—C—C—O torsion angle of 108.16 (15)°. The dihedral angle between the two aromatic rings is 72.00 (6)°. In the crystal structure, neighbouring molecules are linked together by weak intermolecular C—H⋯O hydrogen bonds and weak intermolecular C—H⋯π interactions. In addition, the crystal structure is further stabilized by intermolecular π–π interactions with centroid–centroid distances in the range 3.6000 (8)–3.8341 (8) Å.

Related literature

For bond-length data, see Allen et al. (1987 ▶). For carbonyl–carbonyl interactions, see Allen et al. (1998 ▶). For related structures and applications, see, for example: Fun & Kia, (2008 ▶); Kaftory & Rubin, (1983 ▶); Frey et al. (1995 ▶); Crowley et al. (1983 ▶); More et al. (1987 ▶); Brown et al. (1965 ▶); Gabe et al. (1981 ▶); Kimura et al. (1979 ▶); Stevens & Dubois (1962 ▶); Shimizu & Bartlett, (1976 ▶); Rubin (1978 ▶).

Experimental

Crystal data

C₁₆H₁₄O₂
M _r = 238.27
Monoclinic,
a = 6.5658 (1) Å
b = 7.0916 (1) Å
c = 26.5958 (5) Å
β = 96.473 (1)°
V = 1230.46 (3) Å³
Z = 4
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 100.0 (1) K
0.30 × 0.22 × 0.09 mm

Data collection

Bruker SMART APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2005 ▶) T _min = 0.975, T _max = 0.993
15023 measured reflections
3562 independent reflections
2473 reflections with I > 2σ(I)
R _int = 0.046

Refinement

R[F ² > 2σ(F ²)] = 0.052
wR(F ²) = 0.129
S = 1.04
3562 reflections
165 parameters
H-atom parameters constrained
Δρ_max = 0.34 e Å⁻³
Δρ_min = −0.23 e Å⁻³

Data collection: APEX2 (Bruker, 2005 ▶); cell refinement: APEX2; data reduction: SAINT (Bruker, 2005 ▶); program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2003 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808023386/at2603sup1.cif

e-64-o1615-sup1.cif^{(17.5KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808023386/at2603Isup2.hkl

e-64-o1615-Isup2.hkl^{(174.7KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Selected distances (Å).

Cg1 is the centroid of the C1–C6 benzene ring.

C7—C8

1.5350 (19)

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O1⋯O2	3.1702 (15)
Cg1⋯Cg1ⁱ	3.6000 (8)
Cg1⋯Cg1ⁱⁱ	3.8341 (8)

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Symmetry codes: (i) Inline graphic ; (ii) .

Table 2. Hydrogen-bond geometry (Å, °).

Cg2 is the centroid of the C9–C14 benzene ring.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C2—H2A⋯O1ⁱⁱⁱ	0.93	2.44	3.2573 (18)	146
C14—H14A⋯Cg2^iv	0.93	2.94	3.6105 (15)	130

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Symmetry codes: (iii) Inline graphic ; (iv) .

Acknowledgments

HKF and RK thanks the Malaysian Government and Universiti Sains Malaysia for the Science Fund grant No. 305/PFIZIK/613312. RK thanks Universiti Sains Malaysia for the award of a post-doctoral research fellowship.

supplementary crystallographic information

Comment

Investigation of the photophysical properties of the α-dicarbonyls has focused on the intramolecular carbonyl group electronic interaction as a function of their geometrical relationship. As in previous extensive studies of the photochemistry (Stevens & Dubois, 1962; Shimizu & Bartlett, 1976) of these compounds, biacetyl and benzil were the exclusive experimental vehicles for photophysical study. The structure of vicinal di- and polycarbonyl compounds have been of interest for many years (Rubin, 1978; Crowley et al., 1983; Kaftory et al., 1983; Frey et al., 1995; Kimura et al., 1979). Only a limited amount of data has been gathered from solid-state configurations such as in single crystals or as inclusion dopants in host crystals.

In the title compound (I) (Fig.1), bond lengths, bond angles, and torsion angles of the dicarbonyl unit deviate significantly from normal values (Allen et al., 1987) in order to minimize the repulsive interactions resulting from juxtaposition of dipolar carbonyl groups (Allen et al., 1987). The C7–C8 bond distance connecting the carbonyl units is longer than those in normally sp²–sp² single bonds, such as in butadiene. This is probably the result of decreasing the unfavourable vicinal dipole-dipole interactions. The dicarbonyl unit has s-trans conformation as can be indicated by the torsion angles of O1–C7–C6–C1, and O2–C8–C9–C10 being 169.55 (13) and 179.45 (14)°, respectively. This conformation is substantiated by the torsion angle of O–C–C–O, being 108.16 (15)°. The overal effect is to maximize the distance between the two electronegative oxygen atoms [O1···O2 = 3.1702 (15) Å] and to allow orbital overlap of the dione with the π system of the benzene rings. The dihedral angle between two phenyl rings is 64.74 (5)°. In the crystal structure, neighbouring molecules are linked together by weak intermolecular C—H···O hydrogen bond and weak intermolecular C—H···π interaction. The packing mode (Fig. 2) tend to be dominated by van der Wwaals close packing considerations and the preference for aligning the substituted phenyl rings parallel to each other along the a axis at about 3.6000 (8) – 3.8341 (8) Å.

Experimental

The synthetic method has been described earlier (Frey et al., 1995). Single crystals suitable for X-ray diffraction were obtained by evaporation of an methanol solution at room temperature.