Studies on UV/Vis Absorption Spectra of Azo Dyes. 24. The different effect of a 2‐methoxy and a 3‐methoxy group in 4‐N.N‐diethylaminoazobenzenes on colour

Abstract A number of 2‐ and 3‐methoxy‐substituted‐4‐N.N‐diethylaminoazobenzenes have been prepared and their absorption maxima in ethanol and toluene compared with the corresponding 4‐N.N‐diethylaminoazobenzenes. Both the 2‐ and 3‐methoxy groups cause a bathochromic shift, but the bathochromic shift of a 3‐methoxy group depends on the substituents in the diazo component. With increasing electron‐withdrawing strength of the substituents in the diazo component a progressive enhancement of bathochromic shift appears. In toluene all 3‐methoxy‐substituted dyes absorb at longer wavelengths compared with the 2‐methoxy‐substituted dyes.