Synthesis of derivatives of Naphtol AS containing polar groups and modification used for C.I. Pigment Red 57

The synthesis of derivatives of Naphtol AS containing polar groups (¯COOH, ¯SO3H) and factors affecting the reaction have been studied. Four derivatives of Naphtol AS containing ¯COOH or ¯SO3H groups in the 3- or 4- position of the phenyl ring were synthesized. Derivatives of Naphtol AS as the second coupling component were used in mixed coupling and the effect of its added amount on the colour strength, hue, flowability and dispersing extent (in water) of pigments was studied.