A combined ab initio and gas electron diffraction study of the molecular structure of 1,1-dicyanocyclobutane

Abstract

The molecular structure of 1,1-dicyanocyclobutane was investigated by gas electron diffraction and the results are compared with 4–21G ab initio gradient geometry refinements. In the cyclobutane ring C1–C2 > C2–C3 in contrast to structural trends generally observed for cyclobutyl systems with a single electronegative substituent. The CCN groups are slightly non-linear, with the CN groups bent away from one another. The structural features observed can be rationalized in terms of a special electronic interaction between the geminal cyano groups, which is also suggested by the 13C NMR spectrum.