2-(4-Methoxyphenoxy)pyrazine

In the title compound, C11H10N2O2, the aromatic rings are almost orthogonal to each other [dihedral angle = 86.97 (8)°], with the benzene ring orientated to face one of the pyrazine N atoms. In the crystal, centrosymmetrically related pairs are connected via pairs of C—H⋯π interactions and the dimeric units thus formed pack into undulating layers that stack along the a axis.

In the title compound, C 11 H 10 N 2 O 2 , the aromatic rings are almost orthogonal to each other [dihedral angle = 86.97 (8) ], with the benzene ring orientated to face one of the pyrazine N atoms. In the crystal, centrosymmetrically related pairs are connected via pairs of C-HÁ Á Á interactions and the dimeric units thus formed pack into undulating layers that stack along the a axis.

Related literature
For background to the fluorescence properties of compounds related to the title compound, see: Kawai et al. (2001); Abdullah (2005). For a related structure, see: Nasir et al. (2010).

Comment
On-going structural studies of heterocyclic N-containing derivatives (Nasir et al., 2010) are motivated by an investigation of their fluorescence properties (Kawai et al., 2001;Abdullah, 2005). In this connection, the title pyrazine derivative, (I), was investigated.
With respect to the benzene ring, the pyrazine ring occupies an orthogonal position with the dihedral angle formed between the rings being 86.97 (8) °. The least-squares plane through the pyrazine ring is aligned along the C5···C8 axis of the benzene ring, an arrangement that allows the benzene ring to be directed towards the pyrazine-N1 atom. The C11-O2-C8-C7 torsion angle of -176.93 (14) ° indicates the methoxy group is co-planar with the benzene ring to which it is attached.
The most prominent intermolecular interaction operating in the crystal structure of (I) is of the type C-H···π. This occurs between centrosymmetrically related molecules and involves a benzene-H and the pyrazine ring, Table 1. The dimeric aggregates pack into undulating layers in the bc plane, Fig. 2, which stack along the a axis, Fig. 3.
Experimental 2-Chloropyrazine (2.5 g, 45 mmol) and 4-methoxyphenol (5.6 g, 45 mmol) were refluxed in THF (10 ml) for 5 h. The residue was dissolved in minimum of water (10 ml) and extracted with ether (3 x 10 ml). The ethereal layer was washed with water and dried over anyhydrous sodium sulfate. Recrystallization from ethyl acetate yielded colourless blocks of (I) after a few days.

Refinement
Carbon-bound H-atoms were placed in calculated positions (C-H 0.93 to 0.96 Å) and were included in the refinement in the riding model approximation, with U iso (H) set to 1.2 to 1.5U equiv (C). Some disorder was noted in the benzene ring (manifested in the shorter than usual average C-C bond distance of 1.37 Å). However, multiple sites were not resolved for this ring.