The application of the Biot-Savart law to the ring current analysis of proton chemical shifts—II : An approach to aromatic character in the annulenes

Abstract

A consistent, conceptually simple system for the empirical measurement of aromatic character in annulenes is presented, which is based on the HMO theory with allowance for simple bond alternation. The method, which is potentially applicable to all well-characterized annulenes, assigns an effective bond alternation to each annulene from the measurement of some π-electron property (in this case ring current), which is identified with the aromatic character (AC) thereof. The system is applied to a wide variety of annulenes and compared with other ground state approaches to the study of aromatic character.