Oxidation of hydrazine by iodine in aqueous perchloric acid

King, S.E.; Cooper, John N.

doi:10.1021/ic50189a073

Cited by 7 publications

(6 citation statements)

References 19 publications

(2 reference statements)

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“…(At this acidity a small amount of N 2 H 6 2+ is present and the correction takes this into account.) The decrease in k r (corrected) values as the I - concentration increases clearly shows an additional source of I - suppression which is in agreement with the observations of King et al This can be accounted for by eq 10 in the mechanism, where the reverse reaction of I - with the steady-state intermediate, IN 2 H 4 + , inhibits the rate. The k 1 K A /[1 + ( k - 1 [I - ]/ k 2 )] term in the numerator of eq 16 can be used to fit the data.…”

Section: Resultssupporting

confidence: 89%

“…He suggested that N 2 H 5 + reacted with HOI and with I 2 . The large uncertainties of his data were subsequently questioned by King et al, who showed that at low pH, the reactive species were N 2 H 4 and I 2 . They suggested the mechanism in eqs 2 and 3, where a steady-state species, IN 2 H 4 + , forms and decays to products with k 1 = 4.4 × 10 7 M -1 s -1 and k - 1 / k 2 = 12.0 M -1 , based on a p K a value of 8.5 for N 2 H 5 + .…”

Section: Introductionmentioning

confidence: 98%

“…The overall stoichiometry in eq 1 has been shown to be valid from pH 1 to 9, and the reaction is used in titrimetric methods for the determination of hydrazine . Although some reaction kinetics have been reported, − there is disagreement in regard to the mechanisms and the rate constants.…”

Section: Introductionmentioning

confidence: 99%

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Kinetics and Mechanisms of the Oxidation of Hydrazine by Aqueous Iodine

Liu

Margerum

1998

Inorg. Chem.

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Kinetics for the reactions of I2 with excess N2H5 +/N2H4 and I- are measured by the loss of I3 - over a wide range of acidity from pH 0.35 to 8.0 at 25.0 °C, μ = 0.50 M. Pseudo-first-order rate constants increase by factors of more than 107 with increase of pH, hydrazine, and buffer concentrations. Below pH 1, I2 reacts directly with N2H5 + which has a relative reactivity that is 2.4 × 107 times smaller than N2H4 (the dominant reactant at pH ≥ 1). Kinetic evidence for IN2H4 + as a steady-state species is found below pH 3. From pH 3.5 to 6.3, rate constants are measured by stopped-flow methods and at higher pH by pulsed−accelerated-flow methods. A multistep mechanism is proposed where I2 reacts rapidly with N2H4 to form an I2N2H4 adduct (K A = 2.0 × 104 M-1) that is present in appreciable concentrations above pH 6. The adduct undergoes general base-assisted deprotonation accompanied by loss of I- in the rate-determining step. Subsequent intermediates react rapidly with another I2 to form N2 as a final product. At high pH, hydrazine acts as a general base as well as the initial nucleophile. Rate constants for various bases (H2O, CH3COO-, HPO4 2-, N2H4, and OH-) fit a Brønsted β value of 0.46. Values for the second-order rate constants (M-1 s-1) for I2N2H4 reactions with CH3COO-, HPO4 2-, N2H4, and OH- are 7.5 × 103, 2.0 × 105, 8.5 × 105, and 4.8 × 108, respectively.

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Section: Resultssupporting

confidence: 89%

Section: Introductionmentioning

confidence: 98%

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Kinetics and Mechanisms of the Oxidation of Hydrazine by Aqueous Iodine

Liu

Margerum

1998

Inorg. Chem.

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“…The study of the mechanisms of oxidation of substrates by iodine has been the subject of several studies, but among which no complete agreement is found [1,7,20,23,24,25,26]. The mechanisms of the oxidation of substances by iodine is not only as varied as the number of authors who have published such works, but also as the number of internationally recognized peer reviewed journals in which such work were published [2,7,20,21,22,23,24,25,26,27,28,29]. A further investigation seemed desirable [30,31].…”

Section: Introductionmentioning

confidence: 99%

Computational Study of the Mechanism of the Oxidation of Hydrazine / Hydrazinium Ion by Iodine in the Gas Phase

Shallangwa¹

2015

IJCTC

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The reaction mechanisms of the oxidation of hydrazine / hydrazinium ion by iodine have been studied using 6311+G** basis set of the density functional theory (DFT) method at the B3LYP level of computation. The study shows that the oxidation reactions can proceed via four independent routes or pathways that can be separately monitored. Two of the proposed pathways involved a two-step reaction mechanism each, in which two transition states were produced while each of the other two routes involved three-step reaction mechanism in which three activated complexes were produced. The results obtained were based on the analyses of the computational energetics of the optimized reactants, intermediates, transition states and products of the reaction of iodine with hydrazine / hydrazinium ion. The study showed that all the four proposed routes were possible by comparing the enthalpies of reactions of the four proposed pathways as well as the activation barriers of the respective rate determining steps which were found to be reasonably acceptable. Rate laws, which were consistent with the written mechanisms, were also derived for each of the proposed mechanisms.

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“…This reaction is the basis of one of the standard analytical procedures to titrate hydrazine and related substances, such as isonicotinoyl-hydrazide and hydrazobenzene, which are widely used in the pharmaceutical industry because of their bacteriostatic properties [19][20][21][22]. The mechanism of oxidation of hydrazine and its derivatives by iodine has been the subject of several studies, but among which no complete agreement was found [22][23][24][25][26][27]. A further investigation seemed desirable [28,29].…”

Section: Introductionmentioning

confidence: 99%

MNDO and DFT Computational Study on the Mechanism of the Oxidation of 1,2-Diphenylhydrazine by Iodine

Shallangwa

Uzairu

Ajibola

et al. 2014

ISRN Physical Chemistry

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The reaction mechanisms of the oxidation of 1,2-diphenylhydrazine by iodine have been examined using semiempirical and density functional theory methods, the oxidation proceeded via two independent pathways that can be separately monitored. One pathway involved the chain multistep mechanism. The other pathway occurred via a one-step mechanism in which a “cyclic” activated complex was formed which on disproportionation gave the products. The one-step “cyclic” activated complex mechanism proceeds more rapidly than the chain multistep mechanism. The results were explained by analyses based on computational energetics of the optimised reactants, intermediates, transition states, and products of the reaction of iodine with 1,2-diphenylhydrazine.

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Oxidation of hydrazine by iodine in aqueous perchloric acid

Cited by 7 publications

References 19 publications

Kinetics and Mechanisms of the Oxidation of Hydrazine by Aqueous Iodine

Kinetics and Mechanisms of the Oxidation of Hydrazine by Aqueous Iodine

Computational Study of the Mechanism of the Oxidation of Hydrazine / Hydrazinium Ion by Iodine in the Gas Phase

MNDO and DFT Computational Study on the Mechanism of the Oxidation of 1,2-Diphenylhydrazine by Iodine

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