1,6-Bis(p-tolyloxy)hexane

The title compound, C20H26O2, crystallized with one half-molecule in the asymmetric unit. The whole molecule is generated by inversion symmetry, with the center of inversion being situated at the mid-point of the central –CH2—CH2- bond of the bridging hexane chain. In the crystal, molecules stack in columns along the b axis. C—H⋯π interactions are present within the columns.

The title compound, C 20 H 26 O 2 , crystallized with one halfmolecule in the asymmetric unit. The whole molecule is generated by inversion symmetry, with the center of inversion being situated at the mid-point of the central -CH 2 -CH 2bond of the bridging hexane chain. In the crystal, molecules stack in columns along the b axis. C-HÁ Á Á interactions are present within the columns.

Related literature
For the properties and synthesis of the title compound, see: Saito et al. (1988). For bond-length data, see: Allen et al. (1987).

Comment
The title compound is used as a sensitizer for thermal recording materials, polyester-resin monomers and fire-resistant materials (Saito et al., 1988).
The molecular structure of the title compound is shown in Fig. 1. The bond lengths (Allen et al. (1987) and angles are within normal ranges. It crystallized with half a molecule in the asymmetric unit. The whole molecule is generated by inversion symmetry with the center of inversion being situated at the center of the C10-C10 i bond of the bridging hexane chain [symmetry code: (i) -x, -y, -z + 2].
In the crystal, there are no intermolecular hydrogen bonds present (Fig. 2). The molecules stack in columns along the b axis and within the columns there are C-H···π interactions present (Table 1).

Experimental
The title compound was prepared by the reported procedure (Saito et al., 1988). Anhydrous potassium carbonate (6.2 g, 45 mmol) was added to a solution of 1,6-dibromohexane (2.5 g, 10.25 mmol) and 4-methoxyphenol (3.18 g, 25.6 mmol) in acetonitrile (100 ml). The mixture was stirred overnight at 338 K, and then filtered and the filtrate evaporated under reduced pressure. The residue was subjected to flash chromatography on silica gel, eluting with (10:1/petroleum ether:ethyl acetate) to give the title compound (Yield 2.13 g). Colourless block-like crystals of the title compound were obtained by slow evaporation of a solution in ethanol (20 ml), after ca. 7 days.

Refinement
All the H atoms were positioned geometrically and constrained to ride on their parent atoms: C-H = 0.93 -0.97 Å with U iso (H) = 1.5U eq (C-methyl) and = 1.2U eq (C) for other H atoms.

Figure 1
The molecular structure of the title molecule, with atom labelling. Displacement ellipsoids are drawn at the 50% probability level.  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.