Geometry changes of aryl amino groups resulting from changes in electron withdrawal: an ab initio molecular orbital study

Changes in the geometry of aryl amino groups in aniline, aminopyridines and protonated forms of these molecules have been studied by ab initio 6–31G* molecular orbital calculations. The pyramidal nature of the amino group in aniline is reduced by increased π-electron withdrawal by the ring but coplanarity with the ring (sp2 hybridized nitrogen) only results when a very strongly π-electron withdrawing centre is conjugated with the amino group.