Shift of Aromatic Band in Substituted Benzene

Abstract

THE aromatic band1 found in benzene at 671 cm.-1 shifts as a consequence of mono-substitution (in benzene) to 740-760 cm.-1. In the case of di-substituted benzenes, there is a steady movement to higher frequencies in passing from the ortho- to the para-position ; whereas in the case of para-substituted phenols we find that increase in molecular weight of the para-substituent from methyl to octyl does not shift the absorption band, which is found in all these compounds at 825–830 cm.-1. Less extensive data on the ortho-phenols show no drift in the aromatic band at 750–755 cm as a result of change in the molecular weight of the substituent from methyl to isopropyl. m-Cresol and m-ethyl phenol absorb strongly at 780-785 cm.-1. It would appear that increasing molecular weight by aliphatic substituents does not shift the aromatic band in the mono-substituted phenols.