ABSTRACT
In the cyano group, the nitrogen and carbon atoms are approximately diagonally (sp) hybridized. The bonding, therefore, consists of a (]' bond and further of two 1T bonds at right angles to each other, giving a linear arrangement R-CN. The bond moment (3.5 D) is caused mainly by the lone-pair orbital centered on the nitrogen atom and directed along the CN axis. Furthermore, the 1T orbitals are displaced toward the nitrogen, and the charge distribution may therefore be represent as
R-C=N--- (1)
group. Thus, protonation occurs at the nitrogen atom, and hydrogen bonding and complex formation to Lewis acids generally take place through the lone pair. However, weak complexes formation involving the CN 1T electrons can occur. The large dipole moment of the cyano group can lead to dipole-dipole interactions in pure nitriles (self-association), or form nitriles to other molecules with polar groups. Further, association may take place as a result of interaction between the partial positive charge on the carbon atom and lonepair electrons on other molecules.
