Classification and Structural Characteristics of Conjugated System

Abstract

Conjugated system, the moiety that the electronic orbitals of adjacent atoms or groups overlap, the electrons delocalize and the bond lengths become average, has special electronic effects, i.e., the conjugate effect that is crucial and difficult in organic chemistry course. It is very important to master the classification and structural characteristics of conjugated systems for understanding the conjugate effect, as well as physical and chemical properties of compounds. However, these have not been systematically discussed in general organic chemistry textbooks and literature. Here, the broad and narrow sense of conjugated systems, the classification and structural characteristics of narrow-sense conjugated system, hyper-conjugated system, through-bond and through-space conjugations were illustrated through the molecular structures of examples and the electronic orbital figures of valence bond and molecular orbital theories.