1,5-Dimethoxynaphthalene

The title compound, C12H12O2, lies across an inversion centre. The molecular structure suggests that the methoxy groups in the 1- and 5-positions of the naphthalene moiety do not significantly distort the planar conformation of the ring system, which has a maximum deviation of 0.0025 (9) Å. In the crystal, molecules pack in a herringbone arrangement in layers parallel to (100) and with chains propagating along [101] formed by very weak C—H⋯O interactions.

The title compound, C 12 H 12 O 2 , lies across an inversion centre. The molecular structure suggests that the methoxy groups in the 1-and 5-positions of the naphthalene moiety do not significantly distort the planar conformation of the ring system, which has a maximum deviation of 0.0025 (9) Å . In the crystal, molecules pack in a herringbone arrangement in layers parallel to (100) and with chains propagating along [101] formed by very weak C-HÁ Á ÁO interactions.
EMO would like to thank the University of Cape Coast for assistance with travel and the Department of Chemistry, University of Oxford, for support.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: LH5655).
The colorless single-crystal of 1,5-dimethoxynaphthalene was crystallized while attemping to crystallize the rac-1,1′bi-2-naphthol/1,5-dimethoxynaphalene complex from a blend of methanol/ethylacetate solvents. It crystallizes in the monoclinic space group P2 1 /c with the molecule located on an inversion centre. The refined molecule and the labeling scheme are given in Fig. 1. It exhibits a herringbone packing motif and the molecules are arranged in layers parallel to the lattice plane (100) as shown in Fig. 2. All bond distances and angles fall within expected ranges.
In 1,5-dimethylnaphthalene (Gaultier, et al., 1967;Belskii et al., 1990;Beintema, 1965) as well as those in 1,4-dimethoxynaphthalene (Wiedenfeld, et al., 1999), 1,8-dimethoxynaphthalene (Cosmo et al., 1990), the steric interactions of the methyl groups cause a deviation from planarity in the naphthalene moiety. However, the ten-membered aromatic ring formed by atoms C1-C10 in (I) is planar; the steric interactions of the methoxy and H atoms do not cause any significant deviation from planarity. The exterior C4-C5-C4′ angle (122.13 (9)°; symmetry operator indicated by a prime is -x + 1, -y + 1, -z + 2) in the naphathalene moiety shows no evidence of distortion in the naphthalene core associated with 1,5disubstitutions. This suggests that the methoxy group seems to be restrained in the packing structure as a result of steric interaction between methoxy group and hydrogen atoms that reduce the propensity of the methoxy group to freely rotate in the crystal structure.
The methoxy substituents point away from the centre of the naphthalene moiety and each one forms a weak hydrogen bonded dimer with the neighbouring molecule. Since the molecule sits on an inversion centre, this leads to the formation of chains in the [101] direction (Fig. 3) via the weak intermolecular C-H···O hydrogen bonds involving the methoxy groups (with a C···O distance of 3.495 (1) Å).
In conclusion, the structure suggests that the methoxy groups in 1 and 5 positions around the naphthalene moiety do not significantly distort the planar conformation of the naphthalene, and the size of the groups and their positions are not influenced by steric interactions with the naphthalene moiety.

Refinement
The H atoms were all located in a difference map, but those attached to carbon atoms were repositioned geometrically.
The H atoms were initially refined with soft restraints on the bond lengths and angles to regularize their geometry (C-H in the range 0.93-0.98, O-H = 0.82 Å) and U iso (H) (in the range 1.2-1.5 times U eq of the parent atom), after which the positions were refined with riding constraints (Cooper et al., 2010).

Figure 1
The title compound with displacement ellipsoids drawn at the 50% probability level. H atoms are shown as spheres of arbitary radius [symmetry operator indicated by a prime is -x + 1, -y + 1, -z + 2].

Figure 2
The packing in (I) viewed along [100] and showing the herringbone arrangement.