(1E,3E)-1,4-Bis(4-methoxyphenyl)buta-1,3-diene

The title compound, C18H18O2, which exhibits blue emission in the solid state, is an intermediate in the preparation of liquid crystals and polymers. The molecule is located on an inversion centre. In the crystal, molecules are arranged in a herringbone motif.

The title compound, C 18 H 18 O 2 , which exhibits blue emission in the solid state, is an intermediate in the preparation of liquid crystals and polymers. The molecule is located on an inversion centre. In the crystal, molecules are arranged in a herringbone motif.

Experimental
Research grants from the Department of Science and Technology (DST), Government of India, are gratefully acknowledged. This is contribution No. PPS-300 from PPS-NIIST. GN is grateful to the Council of Scientific and Industrial Research (CSIR) for a research fellowship. Funding from the National Science Foundation (MRI,CHE-0420497) for purchase of the APEXII diffractometer is also acknowledged. (1E,3E)-1,4-Bis(4-methoxyphenyl)buta-1,3-diene G. Narayan, N. P. Rath and S. Das

Comment
Although the crystal structures of a number of butadiene molecules have been reported (George et al., 1998;Vishnumurthy et al., 2002;Davis et al., 2004Davis et al., , 2008Kumar et al., 2009;Ono et al., 2009), that of the title compound, C 18 H 18 O 2 , (I), has not been determined and the structure is reported here (Fig. 1). There are four molecules of (I) per unit cell. The symmetrical molecules are arranged in a herringbone fashion (Koren et al., 2003) in which the molecules are packed in an edge-to-face orientation (Fig. 2).
Thermal properties: On heating, crystals of (I) melted at 237 °C, which on further heating sublimed at 246 °C. The sublimed-condensed crystals were chemically unaltered as evidenced by NMR and MS analyses.

Experimental
A mixture of diethyl-4-methoxybenzylphosphonate (1 equiv) and potassium tert-butoxide (5 equiv) were stirred in dry DMF at room temperature and cooled to 273 K. 4-Methoxycinnamaldehyde (1 equiv) dissolved in dry DMF was slowly added into the solution. The reaction mixture was allowed to stir for 12 h at room temperature. TLC analysis indicated completion of reaction. Reaction mixture was poured into ice water, extracted with dichloromethane and concentrated under reduced pressure. The residue was washed with ethyl acetate and filtered. The compound being insoluble in ethyl acetate remained in the residue. This was repeatedly washed with ethyl acetate (small quantities) to obtain pure title compound. The small amount of compound which remained in the filtrate was recovered by column chromatography through silica gel (100-200 mesh), using 5% ethyl acetate/hexane as the mobile phase. Single crystals obtained from ethylacetate at room temperature were of poor quality (high R value) and the structure determination was carried out at 100 K. Fresh crystals were grown from chloroform/hexanes at room temperature which were of higher quality to permit X-ray analysis at 293 K. The data presented herein are from the latter determination. (1.5 for methyl groups) times U eq (C). Fig. 1. The molecular structure of (I), with atom labels and 50% probability displacement ellipsoids for non-H atoms.