Description:(from preface)The effect of substituents on benzenoid reactivity has been one of the most extensively investigated branches of chemistry. The scattered data on pyridine substitution are now assembled in a review by R. A. Abramovitch and J. G. Saha which is as valuable for showing what remains to be done as for what has been achieved. R. E. Lyle and P. S. Anderson survey reactions of nitrogen heterocycles with complex hydrides, and the heterocyclic chemistry of nitriles and nitrilium salts is covered by P. Johnson and R. Madronero.Each of the remaining three chapters deals with a group of compounds: cyclic en amines (K. Blaha and O. Cervinka), pyrazoles (A. N. Kost and I. I. Grandberg), and physicochemical aspects of purines (J. H. Lister).Suggestions are welcome for contributions to further volumes; they should be in the form of a short synopsis.We thank the Editorial Board, the publishers, and the authors for their cooperation.