organic compounds
The monosubstituted derivative 4-ethynyl[2.2]paracyclophane, C18H16, (I), and the four disubstituted isomers, 4,12-, (II), 4,13-, (III), 4,15-, (IV), and 4,16-diethynyl[2.2]paracyclophane, (V), all C20H16, show the usual distortions of the [2.2]paracyclophane framework. The crystal packing is analyzed in terms of C—Hπ interactions, some with Hπ as short as 2.47 Å, in which the cyclophane rings and/or the triple-bond systems may act as acceptors. For compounds (I) and (IV), the known `7,11'-type cyclophane packing is observed, with a herring-bone pattern of molecules in a layer structure.
organic compounds
In the title compound, C18H16, the [2.2]paracyclophane geometry is restrained to a considerable extent despite the introduction of the extra C=C bridge; typical paracyclophane features, such as the elongated C-C bridges, are still observed. However, the bridgehead atoms of the C=C bridge are forced into unusually close proximity [2.657 (3) Å], which in turn causes the rings to be rotated to an interplanar angle of 13.7 (2)°. The packing involves hexagonally close-packed layers of molecules parallel to the xy plane, corresponding to the known `7,11' pattern of paracyclophanes, but without significant short intermolecular contacts.