Iododurene

The title compound (systematic name: 1-iodo-2,3,5,6-tetramethylbenzene), C10H13I, crystallizes in the chiral space group P212121. The I atom is displaced by 0.1003 (5) Å from the mean plane of the ten C atoms [maximum deviation = 0.018 (6) Å]. In the crystal, there are no significant intermolecular interactions present.


Experimental
Crystal data C 10 H 13 I M r = 260.11 Orthorhombic, P2 1 2 1 2 1 a = 5.5099 (3) Å b = 11.8839 (5) Å c = 15.1704 (6) (Duisenberg et al., 2003); data reduction: EVALCCD (Duisenberg et al., 2003); program(s) used to solve structure: SIR2002 (Burla et al., 2005); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: CAMERON (Watkin et al., 1996) and DIAMOND (Brandenburg, 2012); software used to prepare material for publication: CRYSTALS. Substituted benzene compounds are generally liquid at room temperature so relatively few crystal structure analyses of such compounds have been reported. We have synthesized three mono-halogenated products of duren; chloro-, bromoand iododurene. These derivatives are solid at 293 K and their dielectric behavior depends on the nature of the substituent, and in particular of its mass and volume. Contrary to chlorodurene the title iododurene in the solid phase has a quite low permeability equal to only 2.6, which changes abruptly at fusion to a value of ca. 4 (Balcou et al., 1965). We report herein on its crystal structure.
The molecular structure of the title compound is illustrated in Fig. 1. The molecule is almost planar with the I atom displaced from the mean plane of the nine C atoms [maximum deviation 0.018 (6) Å for the methyl C atoms C7 and C9] In the crystal, the a axis is very short, so the molecules stack along this direction (Fig. 2). The best mean plane passing through the carbon and iodine atoms, calculated with the program Molax of CRYSTALS (Betteridge et al., 2003), indicated that the angle between the normal to this mean plane is ca. 50.1° relative to the a axis, ca. 44.8° relative to the b axis and ca. 74.5° relative to the c axis (Fig. 3).
The crystals obtained sublimate a little at ambient temperature. Moreover, at room temperature iododurene and the isotypic product bromodurene (Charbonneau et al., 1964(Charbonneau et al., , 1965 crystallize in the same orthorhombic space group with fixed orientations of the dipolar grouping not presenting dielectric dispersion. This fact could be interpreted by the importance of the distribution of the masses of the substituents, that inhibit the possibility of molecular reorientation like in chlorodurene (Balcou et al., 1965).

Experimental
The title compound was synthesized by direct iodination of durene. Equimolecular quantities of iodine and durene were dissolved in pure acetic acid at 343 K. Progressive iodination was obtained by oxidation of durene using drops of pure sulfuric and nitric acids diluted in acetic acid. Total precipitation of iododurene was obtained by dilution with water.
Purification was done by chromatography on a silica column and finally precipitation of a solution in chloroform, giving colouress needle-like crystals.

Refinement
All H atoms were localized in a difference Fourier map. The C-bound H atoms were included in calculated positions and treated as riding atoms: C-H = 0.94 Å for CH H atoms, and 0.95 -0.97 Å for CH 3 H atoms, with U iso (H) = k × U eq (C) where k = 1.5 for CH 3 H atoms and = 1.2 for other H atoms.

Figure 1
The molecular structure of the title molecule, with atom numbering. The displacement ellipsoids are drawn at the 50% probability level.  A view along the a axis of the crystal packing of the title compound.

Figure 3
A view along the c axis of the crystal packing of the title compound.

Special details
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.