Free-radical substitution in aliphatic compounds. Part XXVII. Chlorination and bromination of 1-cyanobutane and cyanocyclobutane

1-Cyanobutane and oyanocyclobutane have been chlorinated and brominated in the gas phase over a wide range of temperatures. The results for 1-cyanobutane are compared with previous halogenations of 1-substituted n-butanes. The chlorination of cyanocyclobutane gives a very high trans/cis ratio for the 1-cyano-2-chlorocyclobutane and quite a high trans/cis ratio for the 1,3-product. This is interpreted in terms of an interaction between the π-orbitals of the cyano-group and the half-filled 2p₂ atomic orbital of the radical site. The bromination of cyanocyclobutane is accompanied by a small amount of elimination of HCN; this reaction is increased by addition of HBr or by an increase in the surface area.