FUW TRENDS IN SCIENCE & TECHNOLOGY JOURNAL
(A Peer Review Journal)
e–ISSN: 2408–5162; p–ISSN: 2048–5170
keywords: Hexamethylpararosaniline chloride, bromate ion, redox reaction, outersphere, polymerisation
The kinetics of the oxidation of hexamethylpararosaniline chloride (hereafter referred to as HPR+) by bromate ion have been studied in acidic medium under pseudo-first order conditions of excess [BrO ] at 30 ± 1oC, [H+] = 2.00 × 10-2 mol dm-3, ionic strength, I = 0.5 mol dm-3 (NaCl). The stoichiometry of the reaction was found to be 2:3 mole ratio of HPR to BrO3 ions. The redox reactions at constant hydrogen concentration follows first order with respect to the reductant concentration [HPR+] and the oxidant concentration [BrO ] respectively and second order overall. The rate of reaction increased with increase in hydrogen ion concentration. The overall reaction conforms to the rate law (-d〖[HPR〗^+])/dt= (a + b [H+]2)[HPR+] [BrO ]; a = 9.22 dm6 mol-2 s-1, b = 1.16 dm9 mol-3 s-1. Added anions and cations (X= HCOO–, CH3COO–, Ca2+, Mg2+) to the reaction mixture significantly inhibited the rate of the reaction. Spectroscopic test and Michaelis-Menten analysis showed no evidence of intermediate complex of significant stability. Free radical polymerization test showed no free radicals. Based on the results obtained experimentally, outersphere mechanism is proposed for the hexamethylpararosaniline -BrO reaction.
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