Kinetic Study of the Formation of the Colored Azo Dye (2,2'-(1,4-Phenylenebis (diazene-2,1-diyl)) bis (4-methoxyaniline)) From p-Anisidine

A kinetic study on the preparation of an azo dye from the reaction between 1,4-di ((E)-chlorodiazenyl) benzene and p-anisidine (4-methoxy-aniline), was conducted at 290 K, with a maximum absorption wavelength (lmax) of 398 nm. The reaction was carried out in an acidic medium (pH = 5.27), under optimal conditions determined via UV-visible spectroscopy, at a concentration of 0.001 M. The resulting stoichiometric p- anisidine;azo reagent ratio was 1:2 in aqueous solution. The rate of dye formation was monitored under these conditions, with the rate constant reaching a maximum at 310 K (0.0765 min-1) and exhibiting a minimum at 280 K (0.0395 min-1). Furthermore, the formation of the dye followed pseudo-first-order kinetics relative with p-anisidine. The half-life (t 1/2) of the reactions at different temperatures was calculated as follows: 9.1, 10.8, 13.4, and 17.6 min at 310, 300, 290, and 280 K, respectively.