Structural Studies of Arylazo(α,α-dimethylbenzyl)malononitriles. Evidence against the Correlation between Bond Length and Reactivity in Bond Cleavage Reactions

Article abstract of DOI:10.1246/bcsj.65.2394

The X-ray structures of phenylazo(α,α-dimethylbenzyl)malononitrile and its p-MeO and p-NO2 derivatives were determined to examine the relationship between reactivity and ground state geometry.Although the rate of the C-C bond heterolysis increases in the order p-MeO < H << p-NO2, neither systematic elongation of the C-C bond nor indication of other geometrical changes due to the interaction between the ? orbital of the bond and the ? system of an arylazo group was observed on going from p-Meo to p-NO2.The results provide evidence against Kirby's proposal of a direct relationship between reactivity and bong length, and support Arnett's view that the stability of heterolysis products is not reflected in the bond length.