1,3,5-Tri-p-tolylpentane-1,5-diol

In the title compound, C26H30O2, the central benzene ring forms dihedral angles of 14.85 (15) and 28.17 (14)° with the terminal benzene rings. The dihedral angle between the terminal benzene rings is 32.14 (13)°. The crystal packing exhibits two strong intermolecular O—H⋯O hydrogen bonds, forming directed four-membered co-operative rings. A region of disordered electron density, most probably disordered ethyl acetate solvent molecules, occupying voids of ca 519 Å3 for an electron count of 59, was treated using the SQUEEZE routine in PLATON [Spek (2009 ▶). Acta Cryst. D65, 148–155]. Their formula mass and unit-cell characteristics were not taken into account during refinement. The structure was refined as an inversion twin [absolute structure parameter = −0.3 (4)].

In the title compound, C 26 H 30 O 2 , the central benzene ring forms dihedral angles of 14.85 (15) and 28.17 (14) with the terminal benzene rings. The dihedral angle between the terminal benzene rings is 32.14 (13) . The crystal packing exhibits two strong intermolecular O-HÁ Á ÁO hydrogen bonds, forming directed four-membered co-operative rings. A region of disordered electron density, most probably disordered ethyl acetate solvent molecules, occupying voids of ca 519 Å 3 for an electron count of 59, was treated using the SQUEEZE routine in PLATON [Spek (2009). Acta Cryst. D65, 148-155]. Their formula mass and unit-cell characteristics were not taken into account during refinement. The structure was refined as an inversion twin [absolute structure parameter = À0.3 (4)].

Comment
The synthesis of the title compound has been achieved by the sodium borohydride reduction of the corresponding 1,5diketone by a method reported recently (Paul et al. 2012). The starting diketone, 1,3,5-tris-(p-tolyl)pentane-1,5-dione, was prepared by a greener route slightly deviating from the reported one (Yang et al. 2005). Though, the separation of the diastereomeric mixture posed problems, it was possible to get one diastereomer in pure form. This acyclic pentane-1,5diol can be employed for the generation of heterocyclic compounds like tetrahydropyran. Generally, pentane-1,5-diol derivatives are found to be more valuable than several other diols in connection with drug delivery-enhancing potency, pharmaceutical and cosmetic properties, antimicrobial spectrum and toxicity (Sundberg & Faergemann, 2008). The related compounds whose structures have been solved by X-ray diffraction analysis are 2,2,3,3,4,4-hexafluoropentane-1,5-diol (Ha et al. 2009) and 3-methylenepentane-1,5-diols (Barrett et al. 2000).
In the crystal, there are two strong O-H···O hydrogen bonds (Table 1)

Experimental
To a stirred solution of 1,3,5-tris(p-tolyl)pentane-1,5-dione (0.4 g, 1.0 mmol) in methanol, sodium borohydride (0.08 g, 2.2 mmol) was added in portions in ambient conditions. After the completion of the reaction, the mixture was poured onto crushed ice and filtered off. The organic layer was dried over anhydrous sodium sulfate. The diastereomeric mixtures were separated by column chromatography using a mixture of petroleum ether and ethyl acetate (80:20) as eluent. The isolated compound was recrystallized in ethyl acetate to obtain colourless plate-like crystal of the title compound in good yield [0.344 g; 86%].

Refinement
All H-atoms were positioned geometrically and allowed to ride on their parent atoms: O-H = 0.84 Å, C-H = 0.95, 0.99, 1.00 and 0.98 Å for CH(aromatic), CH 2 , CH and CH 3 H atoms, respectively, with U iso (H) = 1.5U eq (C-methyl and O) and = 1.2U eq (C) for other H atoms. The disordered solvent molecules occupy ca. 14.3% of the unit-cell volume. This region of disordered electron density, probably disordered ethyl acetate solvent molecules, was treated with the SQUEEZE routine in PLATON (Spek, 2009), and the solvent-free model was employed for the final refinement.

Figure 1
The molecular structure of the title molecule, with atom labelling. Displacement ellipsoids are drawn at the 30% probability level.