Kinetics of Iodous Acid Disproportionation

Abstract

The iodous acid disproportionation is autocatalytic, and it is not easy to measure the rate constant of the step 2IO 2 H → IO 3 − + IOH + H + separately. Hg(II) was used previously to suppress the autocatalytic pathway, but this method presents difficulties discussed in this work. A more effective method is the use of crotonic acid, an effective IOH scavenger. It suppresses side reactions, and a purely second-order rate law is obtained. The rate constant decreases from 5 to 0.2 M −1 s −1 when the sulfuric acid concentration increases from 0.08 to 0.60 M. The observed decrease could be explained if IO 2 − reacts faster than IO 2 H. This may have consequences for the mechanism of the oscillating Bray-Liebhafsky reaction. C 2013

Reexamination of Gas Production in the Bray–Liebhafsky Reaction: What Happened to O2 Pulses?

“…Still, this is most likely not the final mechanism of the BL reaction, as the field remains quite active. Important information continues to be published, regarding the kinetics of the relevant chemistry of iodine, − as well as the role of radicals in the reaction, − the overall dynamics of oscillations, , or new methods applicable to their monitoring …”

Kinetics and mechanism of I(+ 3) reactions and consequences for other iodine reactions

“…The section "I(+3) disproportionation" proposes a new interpretation of our kinetic study of the reaction 2 HOIO  IO3 -+ HOI + H + (R13) published previously [26]. The section "I(+3) autocatalytic disproportionation" presents a new kinetic study of the reaction HOI + HOIO  IO3 -+ I -+ 2 H + (-R1) and the next section presents a new kinetic study of the oxidation of I(+3) by H2O2 (R9).…”

Practical Chemical Actinometry—A Review

“…The subsequent reaction, which involves HOI, OIand I 2 OH -, must be pHdependent. HIO 2 produced by reaction 37 oxidizes iodide, producing additional hypoiodous acid according to equilibrium reaction 38 (81), which competes with disproportionation of HIO 2 (reaction 39) (81,82).…”

“…HIO 2 produces IO 3 by reaction with HOI or with its protonated form H 2 OI + , according to equilibrium 40 and reaction 41 (81,82).…”