The alkyl group on the imino bridge of heterobifunctional reactive dyes plays a major role in improving the dyeing properties. The configurations of a pair of model compounds 2,4-dimethoxy-6-anilino-s-triazine and 2,4-dimethoxy-6-(N-metyl-anilino)-s-triazine have been determined by X-ray diffraction analysis of single crystals. The planar angle between the triazinyl and phenyl rings of the above models are 8.35° and 72.22° respectively. It indicates that the steric effect of the ethyl group produces a non-planar configuration and leads to the improvement of the dyeing properties.
