The kinetic reactions were studied for formation of colored complexes derived from the electron-donating paracetamol with the two diazotized reagents: (sulfanilic acid sodium salt) and (para-nitro aniline) accepting these electrons at a temperature of (25°C) and at different pH .

The formation kinetics of the above complexes was followed spectrophotometrically at the optimal conditions for each of them, after determining the optimal mole ratios for the concentrations of the components of each complex, which were (1:10) for (drug: reagent), respectively. And our current study proved that these interactions are Pseudo-first-order relative to the paracetamol drug. We were able to calculate the rate constant for the formation of the two produced compounds (k1). The highest value for the compound (Paracetamol Drug+Diazotized Sulfanilic Acid Sodium Salt) is (0.0328 at pH9.2), and for the compound (Paracetamol Drug +Diazotized para-Nitro Aniline) is (0.0305 at pH9.2). We also calculated the half-life-time (t1/2) for each of them, and it was (21.1min.) and (22.7min.), respectively, which is completely opposite to the values of their rate constants under the same conditions.