The effect of lateral methyl substitution on the mesophase behaviour of aryl 4-alkoxyphenylazo benzoates

Abstract

In order to investigate the effect of lateral methyl substitution on the mesophase behaviour of the previously investigated laterally neat 4-substituted phenyl 4ʹ-(4ʺ-alkoxyphenylazo) benzoates (Ina–e), five homologous series of 4-substituted phenyl 4ʹ-(3ʺ-methyl-4ʺ-alkoxyphenylazo) benzoates (IIna–e) were prepared in which, within each homologous series, the length of the terminal alkoxy group varies between 8, 10, 12, 14, and 16 carbons, while the other terminal substituent, X, is a polar group that alternatively changed between the electron-donating CH3O and CH3 groups, and the electron-withdrawing Br and CN groups, in addition to the unsubstituted analogue. Two other isomeric series (IIIna–e) were also prepared in which the methyl group is laterally attached, this time, to position 2 of the same ring, aiming to investigate the effect of the different orientation of the methyl groups on the mesophase behaviour of the produced isomers. The results were discussed in terms of steric, mesomeric, and polarisability effects.