Benzonitrile oxides dimerize in solution to form a furoxan, a dioxadiazine, or an oxadiazole-N-oxide. We are using single-crystal X-ray diffraction to examine whether the molecular packing arrangement in a crystalline benzonitrile oxide might determine which of these dimers is formed in a solid-state dimerization. To determine any role of halogen bonding in establishing the nitrile oxide crystal structure, we have determined the X-ray crystal structure of 2,6-dichlorobenzonitrile oxide, which has a reported stability of approximately 30 days at room temperature. The compound crystallizes in space group P21/c with four molecules in general positions within the monoclinic unit cell. The fulminate group is bent slightly at the carbon atom, with a C-C-N bond angle of 173(2) degrees. Our prior determination of 4-chlorobenzonitrile oxide had revealed a close intermolecular oxygen…chlorine contact but no close chlorine…chlorine contacts, but we find 2,6-dichlorobenzonitrile oxide to exhibit close intermolecular chlorine…chlorine contacts but no close oxygen…chlorine contacts.

Crystal structures of reactive nitrile oxides:  2,6-Dichlorobenzonitrile oxide

251st National Meeting (2016)

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