Rate Law and Mechanism of the Reaction of Iodine with Tetrathionate Ion

Awtrey, Alice D.; Connick, Robert E.

doi:10.1021/ja01154a015

Cited by 71 publications

(118 citation statements)

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“…In this paper, the spectrometric analysis was conducted at 353 nm with a single beam, where the interference with iodide ion and solvent absorption could be reduced. At 353 nm, e was 2624 m 2 mol -1 , which is in good agreement with the literature [1,24].…”

Section: Determination Of Molar Extinction Coefficientsupporting

confidence: 91%

Micromixing of Solid‐liquid Systems in a Stirred Tank with Double Impellers

et al. 2013

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The effect of solid particles on micromixing has been studied using the competitive iodide/iodate reaction system in stirred, multi-impeller, solid-liquid systems. The influences of particle size, impeller speed, solid holdup, feed position, and energy input have been investigated. The change of the segregation index with the power input was more distinguishable only for the 450-600 lm particles as compared with the large ones, at the same solid holdups. Also, for the small ones, cloud formation was observed at a particle concentration of 12.1 wt %. However, the influence of larger particles of 1-1.25 mm on micromixing was negligible, though both energy input and solid loading were increased. Besides, the optimal feed position was identified, and multiple feeds were also explored.

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Section: Determination Of Molar Extinction Coefficientsupporting

confidence: 91%

Micromixing of Solid‐liquid Systems in a Stirred Tank with Double Impellers

et al. 2013

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“…Although it was suggested that 12 is an obligatory intermediate (Thomas & Hager, 1969), there is evidence indicating that I2 is not the active iodinating agent in thyroid peroxidasecatalyzed iodination (Taurog, 1970). Other experimental results support the conclusion that iodination does not occur by way of free 12, but rather via an iodinating species associated with the enzyme (Bayse & Morrison, 1971;Pommier et al, 1973;Davidson et al, 1978). It has been suggested that the iodinating species is enzyme-activated hypoiodous acid, HOI, on the basis of a kinetic analysis of tyrosine iodination catalyzed by HRP' at low pH (Dunford & Ralston, 1983).…”

mentioning

confidence: 65%

Kinetics and mechanism of the peroxidase-catalyzed iodination of tyrosine

Sun¹,

Dunford²

1993

Biochemistry

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The kinetics of iodination of tyrosine by hydrogen peroxide and iodide, catalyzed by both horseradish peroxidase (HRP) and lactoperoxidase (LPO), were studied. The initial rates of formation of both molecular I2 and monoiodotyrosine (MIT) were measured with stopped flow techniques. The following reactions occur in both systems. Enzymatic: FeIII + H2O2-->Fev = O + H2O; Fev = O + I(-)-->FeIII-O-I-; FeIII-O-I- + H(+)-->FeIII + HOI; FeIII-O-I- + I- + H(+)-->FeIII + I2 + HO-. Iodine equilibria: I2 + I-<-->I3-; I2 + H2O<-->HOI + I- + H+. Nonenzymatic iodination, one or both of the following: Tyr + HOI-->MIT + H2O; Tyr + I2-->MIT + I- + H+, where FeIII is native peroxidase, Fev = O is compound I and Tyr is tyrosine. The big difference in the two systems is that the following reaction also occurs with LPO: FeIII-O-I- + Tyr-->MIT + FeIII + HO-, which is the dominant mechanism of iodination for the mammalian enzyme. The overall rate of formation of MIT is about 10 times faster for LPO compared to HRP under comparable conditions. A small decrease in rate occurs when D-tyrosine is substituted for L-tyrosine in the LPO reaction. Thus LPO has a tyrosine binding site near the heme. A kinetically controlled maximum is observed in I3- concentration. Once equilibrium is established, I2 is the dominant form of inorganic iodine in solution. However, hypoiodous acid may be the inorganic iodination reagent.

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“…The value for the formation constant of 13-from 12 and I-was taken as 714 [7]. The two wavelengths used in this work were 470 nm (mainly due to 12) and 353 nm (mainly due to I3-).…”

Section: Molar Absorbancesmentioning

confidence: 99%

“…Molar absorbances for 13-were taken as 26,400 at 353 nm and 730 at 470 nm. For 12 the values used were 18 at 353 nm and 730 at 470 nm [7].…”

Section: Molar Absorbancesmentioning

confidence: 99%

Kinetics and mechanism for the iodination of methylmalonic acid

Furrow

1979

Int J of Chemical Kinetics

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The reaction CH(CH3)(COOH)z + 12 = CI(CHB)(COOH)~ + H+ + I-was followed spectrophotometrically a t 353 nm and 470 nm a t 25°C under various conditions of pH and methylmalonic acid concentration. The equilibrium constant for the reaction is 0.11 f 0.02. An iterative technique was used to integrate postulated rate equations. Agreement between experimental and calculated absorbance versus time curves was generally better than 0.005 A (approximately 5% of maximum) a t both wavelengths for a mechanism where the ratedetermining step is formation of an enolate (k = 1.63 X f 0.03 X sec-'). The enolate may be rapidly transformed to the enol or enol carboxylate anion depending on the pH. All three forms are rapidly iodinated. The mechanism of general base catalysis is supported by rate increases proportional to base concentration in buffer solutions. The bases, acetate ion, chloracetate ion, sulfate ion, dichloracetate ion, and water, follow a Br6nsted relationship with B = 0.7.

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Rate Law and Mechanism of the Reaction of Iodine with Tetrathionate Ion

Cited by 71 publications

References 1 publication

Micromixing of Solid‐liquid Systems in a Stirred Tank with Double Impellers

Micromixing of Solid‐liquid Systems in a Stirred Tank with Double Impellers

Kinetics and mechanism of the peroxidase-catalyzed iodination of tyrosine

Kinetics and mechanism for the iodination of methylmalonic acid

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