The Nitro Group as Substituent

摘要

The nitro group is an outstanding substituent which should be included whenever possible in studies of substituent effects: its effects are strong and can be quantitatively estimated with reliability. On the other hand, the theoretical interpretation of these effects is not always unambiguous, particularly the existence of resonance. The idea of separating inductive and resonance effects evidently has its limits and the term resonance should generally be used in a quantitative sense with respect to certain observable quantities. Resonance is certainly not present, or at least not observable, in every single case where resonance formulae have been written in the literature.