Abstract
The kinetics of the redox reaction between naphthol green B and hydrazine dihydrochloride has been studied in aqueous hydrochloric acid medium at an ionic strength, I = 0.50 mol dm-3(NaCl), [H+] = 1.0×10-4 moldm-3 (HCl) and T = 21±1°C. The redox reaction displayed a stoichiometry of 1:1 and obeys the rate law: -d[NGB3-]/dt=k2[NGB3-][N2H4.2HCl]. Change in hydrogen ion concentration of the reaction medium has no effect on the rate of the reaction. Added cations and anions inhibited the rate of the reaction. The redox reaction showed negative salt effect, with the rate decreasing with increase in ionic strength of the reaction medium. Results of the Michaelis–Menten’s plot show that an intermediate complex was not formed during the course of the reaction. The outersphere mechanism is proposed for this reaction.
Highlights
Naphthol green B (NGB3-) is used in the production of drugs, cosmetics and for staining purposes
The stoichiometric studies showed that one mole of naphthol green B was consumed by one mole of N2H4.2HCl
The linearity of the pseudo-first order plots (Figure 1) suggests a first order dependence of reaction rate on [NGB3-] and [N2H4.2HCl] under the experimental conditions employed in this investigation
Summary
Naphthol green B (NGB3-) is used in the production of drugs, cosmetics and for staining purposes. A new amperometric glucose biosensor with naphthol green B as a mediatior has been reported [1]. Hydrazine dihydrochloride, which is a powerful reducing agent, has similarity to the thiourea by possessing nitrogen in its structure can be possible inhibitor and similar compounds [2]. Kinetic study of the oxidation of hydrazine dihydrochloride by aqueous iodine has been reported [3]. Reduction of aqueous silver nitrate by hydrazine dihydrochloride in weakly alkaline solution results in a polydisperse colloid that is stable for many months without addition of any stabilizing compounds [4]. This work is carried out to further understand the reaction of naphthol green B and that of hydrazine dihydrochloride
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