4-Chloro-2′,4′,6′-triethyl­benzophenone: a redetermination

Hiroki Takahashi

doi:10.1107/S1600536811009639

. 2011 Mar 19;67(Pt 4):o935. doi: 10.1107/S1600536811009639

4-Chloro-2′,4′,6′-triethylbenzophenone: a redetermination

Hiroki Takahashi ^a,^*

PMCID: PMC3099762 PMID: 21754204

Abstract

The structure of the title compound [systematic name: (4-chlorophenyl)(2,4,6-trimethylphenyl)methanone], C₁₉H₂₁ClO, has been redetermined at 100 K. The redetermination is of significantly higher precision than the previous structure determination at 133 K and reveals disorder of the one of the o-ethyl groups [occupancy factors = 0.77 (1) and 0.23 (1)] that was not identified in the previous report [Takahashi & Ito (2010 ▶). CrystEngComm, 12, 1628–1634]. The C—C—C—C torsion angles of the major and minor disorder components of the ethyl group with respect to the attached benzene ring are −103.7 (2) and −172.0 (6)°, respectively. It is of interest that the title compound does not display a single-crystal-to-single-crystal polymorphic phase transition on cooling, as was observed for a closely related compound, a fact that can be attributed to the disorder in the ethyl group.

Related literature

For the structure of the title compound at 133 K and the phase transition observed in a related compound, see: Takahashi & Ito (2010 ▶). For its solid-state photochemical properties, see: Ito et al. (2009 ▶). For the synthesis, see: Ito et al. (1985 ▶).

Experimental

Crystal data

C₁₉H₂₁ClO
M _r = 300.81
Monoclinic,
a = 10.3329 (6) Å
b = 15.8383 (8) Å
c = 10.6876 (6) Å
β = 111.0116 (16)°
V = 1632.78 (16) Å³
Z = 4
Mo Kα radiation
μ = 0.23 mm⁻¹
T = 100 K
0.35 × 0.27 × 0.20 mm

Data collection

Rigaku R-AXIS RAPID diffractometer
Absorption correction: multi-scan (ABSCOR; Higashi, 1995 ▶) T _min = 0.745, T _max = 1.000
15675 measured reflections
3738 independent reflections
3287 reflections with I > 2σ(I)
R _int = 0.032

Refinement

R[F ² > 2σ(F ²)] = 0.040
wR(F ²) = 0.104
S = 1.08
3738 reflections
264 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.43 e Å⁻³
Δρ_min = −0.19 e Å⁻³

Data collection: RAPID-AUTO (Rigaku, 1998 ▶); cell refinement: RAPID-AUTO; data reduction: Yadokari-XG 2009 (Kabuto et al., 2009 ▶); program(s) used to solve structure: SIR97 (Altomare et al. (1999 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: Yadokari-XG 2009 and ORTEP-3 (Farrugia, 1997 ▶); software used to prepare material for publication: Yadokari-XG 2009 and publCIF (Westrip, 2010 ▶).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536811009639/sj5114sup1.cif

e-67-0o935-sup1.cif^{(21KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536811009639/sj5114Isup2.hkl

e-67-0o935-Isup2.hkl^{(183.3KB, hkl)}

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

supplementary crystallographic information

Comment

The title compound, 4-chloro-2',4',6'-triethylbenzophenone, is analogous to 3,4-dichloro-2',4',6'-triethylbenzophenone that undergoes a single-crystal-to-single-crystal polymorphic phase transition on cooling the crystal to 166 K (Takahashi & Ito 2010). In this phase transition one of the o-ethyl groups rotates by 180 °.

Crystal structures of the title compound at 133 K and 173 K were already reported (Takahashi & Ito, 2010: Ito et al. 2009). The crystal structure of the title compound has been redetermined at 100 K. This crystal does not show the same phase transition in this temperature range. However in this structure, one of o-ethyl groups was disordered over two positions with a site-occupancy ratio of 0.77 (1) and 0.23 (1). The molecular structure of the title compound is shown in Fig. 1. The dihedral angles of the C1—C6—C18—C19 (major disorder component) and C1—C6—C18B—C19B (minor component) are -103.7 (2) and -172.0 (6) °, respectively. This disordered ethyl group operates as a buffer in the crystal on shrinking the crystal lattice, hence this compound does not show the phase transition at low temperature.

Experimental

The title compound was prepared from 1,3,5-triethylbenzene and 4-chlorobenzoyl chloride by a Friedel-Crafts reaction as described in the literature (Ito et al. 1985). Colourless prism-like crystals were obtained by slow evaporation of an MeOH solution of the title compound.