4-(Prop-2-yn-1-yloxy)benzene-1,2-dicarbonitrile

In the title compound, C11H6N2O, the complete molecule is generated by the application of crystallographic twofold symmetry (the molecule is disordered about this axis). The prop-2-yn-1-yl residue is slightly twisted out of the plane of the benzene ring [C—O—C—C torsion angle = 173.1 (3)°] and is orientated away from the nitrile substituents. In the crystal, supramolecular chains along the a axis, arising from C—H⋯N interactions, are connected into stacks along the c axis by π–π interactions between the benzene rings [centroid–centroid distance = 3.6978 (6) Å = length of the c axis].

In the title compound, C 11 H 6 N 2 O, the complete molecule is generated by the application of crystallographic twofold symmetry (the molecule is disordered about this axis). The prop-2-yn-1-yl residue is slightly twisted out of the plane of the benzene ring [C-O-C-C torsion angle = 173.1 (3) ] and is orientated away from the nitrile substituents. In the crystal, supramolecular chains along the a axis, arising from C-HÁ Á ÁN interactions, are connected into stacks along the c axis byinteractions between the benzene rings [centroid-centroid distance = 3.6978 (6) Å = length of the c axis].
In (I), Fig. 1, the complete molecule is generated by the application of 2-fold symmetry; the molecule is disordered about this axis. The O1 and C1 atoms lie -0.067 (3) and 0.059 (2) Å out of the plane through the benzene ring, respectively. The prop-2-yn-1-yl is twisted out of the plane of the benzene ring as seen in the value of the C4-O1-C5 -C6 torsion angle of 173.1 (3)° and is orientated in the opposite direction to the nitrile substituents.
In the crystal packing, supramolecular chains along the a axis feature owing to C-H···N interactions, Table 1, and 10membered {···HC 3 N} 2 synthons, Fig. 2. Chains are connected into stacks along the c axis by π-π interactions between the benzene rings [inter-centroid distance = 3.6978 (6) Å = length of the c axis]. The layers inter-digitate along the b axis with no specific intermolecular interactions between them.

Experimental
The title compound was prepared by modification of literature procedures (Wu et al., 1998;Seven et al., 2009). Under a nitrogen atmosphere, anhydrous potassium carbonate (1.12 g, 8.1 mmol) was added in two portions at 1 h intervals to a solution of propargyl alcohol (1.5 ml, 26.0 mmol) and 4-nitrophthalonitrile (0.70 g, 4.04 mmol) in dry N,N-dimethylformamide (7 ml). After 96 h, the crude reaction mixture was poured into water (140 ml). The green precipitate was collected by vacuum filtration, washed with water and dried. The crude product was purified by silica gel column chromatography using dichloromethane as eluent to provide 0.4 g (63.9%) of a faintly coloured solid that was recrystallized from CH 2 Cl 2 / hexane as colourless prisms.

Refinement
With the exception of the acetylenic H-atom which was refined freely, carbon-bound H-atoms were placed in calculated parameters of the O1 and C4 atoms were tightly restrained to be nearly isotropic.

Figure 1
The molecular structure of (I) showing displacement ellipsoids at the 50% probability level. The molecule is disordered about the 2-fold axis -only one orientation is shown.   A view of the supramolecular layer in the ac plane in (I). The C-H···O and π-π interactions are shown as blue and purple dashed lines, respectively. Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. 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.