Kinetics of Disproportionation and pKa of Bromous Acid

Abstract

The kinetics of the disproportionation reaction of bromine(III), 2Br(III) -Br(1) + Br(V), was studied in phosphate buffer, in the pH range 5.9-8.0, by monitoring optical absorbance at 294 nm using stopped-flow,The dependences on C?H+ and [Br(III)] were of order 1 and 2, respectivley, and no dependence on [Br-] was found. The reaction was also studied in acetate buffer, in the pH range 3.9-5.6. Within experimental error, no evidence was found for a direct reaction between two BrO2-ions. This study yields rate constants 39.1 f 2.6 M-I s-l for the reaction HBrO2 + BrO2--HOBr + Br03-and 800 f 100 M-' for the reaction 2HBr02 -HOBr + Br03-+ H + and an equilibrium quotient for HBr02 e H + + BrOz-of 3.7 f 0.9 X 10-4 M (pKa = 3.43) at ionic strength 0.06 M and 25.0 f 0.1 OC. The bromous acid dissociation constant is essentially identical to the value previously obtained from a kinetics study of the bromine(II1)-I-reaction (J. Phys. Chem. 1992, 96, 6861).

Energy cycle based on a high specific energy aqueous flow battery and its potential use for fully electric vehicles and for direct solar-to-chemical energy conversion

“…The kinetics of the bromine disproportionation (8) has been studied mostly in near-neutral media (4≤pH≤ 8) [58,59] where the rates of various steps fall in the range convenient for experimental measurements. The process is rather complex (the corresponding reactions for chlorine being even more complex) [60][61][62][63] [73,74].…”

Study on the Indirect Electrochemical Detection of Ammonium Ion with In Situ Electrogenerated Hypobromous Acid

“…At pH 7, the absorbance around 260 nm was decreased. According to the equilibrium equation (3), bromine was thought to be disproportionated to HBrO, which shows the absorption maximum at 260 nm but has relatively low molar absorptivity value (95 M -1 cm -1 ) [19]. In the basic region, HBrO is dissociated to BrO -with the absorption maximum at 329 nm [20].…”

Measurements and Simulations of the Acidity Dependence of the Kinetics of the Iron-Catalyzed Belousov–Zhabotinsky Reaction: Proton-Catalysis in the Electron Transfer Reaction Involving the [Fe(phen)3]3+ Species

“…The disproportionation of bromous acid 2HOBrO → HOBr + BrO 3 – + H + plays a prominent role as “reaction 4” (or R4 for short) because it is the determining step for the onset of the catalyst oxidation with r 4 = k 4f [HOBrO] 2 , and this reaction was considered to involve two neutral HBrO 2 molecules. The reaction rate constant k 4f was measured under many conditions by various groups with estimates of k 4f ranging over seven magnitudes from 4 × 10 +8 to 39 M –1 s –1 , and these studies − have been reviewed (cf. Table 1 in ref ).…”