Tuning Aromaticity of para-Substituted Benzene Derivatives with an External Electric Field.

Substituent effects are phenomena which play an important role in organic chemistry, especially when aromatic species are considered. For this class of systems, the question of the interrelation between substituent effect and aromaticity arises. The relationship between aromaticity and substituent effects appears to be of a competitive nature. This work examines changes in aromaticity in para-substituted benzene derivatives exposed to external electric fields of various intensities. Three systems with different substituent electron-accepting/donating properties are studied, namely p-aminophenol, p-nitrobenzonitrile and p-nitrophenol. In these cases, the competitive character between substituent effects and aromaticity is emphasised. It is also shown that aromaticity (and the substituent effect) can be tuned using an external electric field applied to the system.