Oxidations of hydrazine and substituted hydrazines by hexachloroiridate(IV) in aqueous solution: Kinetic and mechanistic analyses

Nan, Chunxia; Dong, Jingran; Tian, Hui Qiao; Shi, Hongmei; Shen, Shigang; Xu, Jin-Quan; Li, Xinghua; Shi, Tiesheng

doi:10.1016/j.molliq.2018.01.143

Cited by 19 publications

(14 citation statements)

References 48 publications

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“…For probing some useful information in the reaction course of BH with [IrCl 6 ] 2− , rapid scan spectra were recorded on the stopped-flow spectrometer under a set of reaction conditions. The obtained spectra are shown in Figure 1, which are similar to those acquired previously in the oxidations of INH and hydrazines with [IrCl 6 ] 2− [14,28]. This type of rapid scan spectra renders a few salient features [14,28]: (1) neither a substitution reaction on the Ir(IV) complex nor a strong association between the [IrCl 6 ] 2− and BH before the rate-determining step(s) underwent since the two disappearing bands around 428 and 488 nm which originate from [IrCl 6 ] 2− showed no shifts and no new absorption bands emerged.…”

Section: Spectral Analysis Of Reaction Coursesupporting

confidence: 81%

“…the ratios in Table 1 point to a clean stoichiometry of ∆[IrCl6 2− ]:∆[Hydrazide]tot = 4:1. The same reaction stoichiometry was also derived previously for the oxidations of INH and hydrazines [14,28]. The stoichiometric reaction in the present cases can be described by Equation 3, where n = 0 for BH and n = 1 for PAH [14].…”

Section: Product Analysissupporting

confidence: 63%

“…the experimental section below). From the spectrophotometric titration data, plots of the measured absorbance at 488 nm as a function of [BH] [14,28]. The stoichiometric reaction in the present cases can be described by Equation (3), where n = 0 for BH and n = 1 for PAH [14].…”

Section: Evaluation Of the Reaction Stoichiometrymentioning

confidence: 97%

“…Spectrophotometric titration was proved to be a good method for determinations of reaction stoichiometries [14,28,29]; it was thus used in the present reaction systems (cf. the experimental section below).…”

Section: Evaluation Of the Reaction Stoichiometrymentioning

confidence: 99%

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Oxidations of Benzhydrazide and Phenylacetic Hydrazide by Hexachloroiridate(IV): Reaction Mechanism and Structure–Reactivity Relationship

Zhang

2020

Molecules

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Benz(o)hydrazide (BH) is the basic aryl hydrazide; aryl hydrazides have been pursued in the course of drug discovery. Oxidations of BH and phenylacetic hydrazide (PAH) by hexachloroiridate(IV) ([IrCl6]2−) were investigated by use of stopped-flow spectral, rapid spectral scan, RP-HPLC and NMR spectroscopic techniques. The oxidation reactions followed well-defined second-order kinetics and the observed second-order rate constant k′ versus pH profiles were established over a wide pH range. Product analysis revealed that BH and PAH were cleanly oxidized to benzoic acid and phenylacetic acid, respectively. A reaction mechanism was proposed, resembling those suggested previously for the oxidations of isoniazid (INH) and nicotinic hydrazide (NH) by [IrCl6]2−. Rate constants of the rate-determining steps were evaluated, confirming a huge reactivity span of the protolysis species observed previously. The enolate species of BH is extremely reactive towards reduction of [IrCl6]2−. The determined middle-ranged negative values of activation entropies together with rapid scan spectra manifest that an outer-sphere electron transfer is probably taking place in the rate-determining steps. The reactivity of neutral species of hydrazides is clearly not correlated to the corresponding pKa values of the hydrazides. On the other hand, a linear correlation, logkenolate = (0.16 ± 0.07)pKenol + (6.1 ± 0.8), is found for the aryl hydrazides studied so far. The big intercept and the small slope of this correlation may pave a way for a rational design of new antioxidants based on aryl hydrazides. The present work also provides the pKa values for BH and PAH at 25.0 °C and 1.0 M ionic strength which were not reported before.

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Section: Spectral Analysis Of Reaction Coursesupporting

confidence: 81%

Section: Product Analysissupporting

confidence: 63%

Section: Evaluation Of the Reaction Stoichiometrymentioning

confidence: 97%

Section: Evaluation Of the Reaction Stoichiometrymentioning

confidence: 99%

See 2 more Smart Citations

Oxidations of Benzhydrazide and Phenylacetic Hydrazide by Hexachloroiridate(IV): Reaction Mechanism and Structure–Reactivity Relationship

Zhang

2020

Molecules

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“…The reaction stoichiometry was investigated by spectrophotometric titrations as we have used recently . The measured absorption values for the series of reaction mixtures as a function of [HONH 2 ] tot are shown in Figure .…”

Section: Resultsmentioning

confidence: 99%

New kinetic and mechanistic findings in the oxidation of hydroxylamine by Cerium(IV) in perchloric acid media

Tian

Yao

et al. 2018

Int J of Chemical Kinetics

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The oxidation of hydroxylamine (HONH 2 ) by Ce(IV) in perchloric acid media took place fast and was followed by a stopped-flow spectrometer. A rate law of −d[Ce(IV)] tot /dt = k ′ [HONH 2 ] tot [Ce(IV)] tot was proved, where k ′ stands for the observed second-order rate constant and [Ce(IV)] tot and [HONH 2 ] tot represent the total concentrations of Ce(IV) and HONH 2 , respectively. The dependencies of k ′ on [H + ] and on ionic strength were investigated. Rapid scan spectra recorded for a typical reaction course and a stoichiometric measurement unraveled several additional characters for the redox reaction. Based on experimental results, a reaction mechanism is proposed, which involves Ce 4+ , Ce(OH) 3+ , and Ce(OH) 2 2+ attacking on HONH 3 + in parallel. Moreover, these parallel attacking reactions are the ratedetermining steps, generating free radicals • ONH 2 , which are rapidly oxidized to nitrate by Ce(IV). Rate constants of these rate-determining steps have been evaluated; a reactivity trend of Ce 4+ > Ce(OH) 3+ > Ce(OH) 2 2+ is disclosed, but the reactivity differences among them are very small. The rate-determining steps are rationalized in terms of an outer-sphere electron transfer, and possible transition states are proposed in the cases of Ce(OH) 3+ and Ce(OH) 2 2+ to account for the small reactivity differences. The obtained kinetic and mechanistic results in the present work are compared with those acquired previously for the same reaction but in sulfuric acid and nitric media. It is concluded that the reaction media can play a dominant role in determining the reaction kinetics, mechanisms, and the product(s) in the oxidation of hydroxylamine by Ce(IV). K E Y W O R D SCe(IV), hydroxylamine, kinetic mechanism, oxidation 856

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Kinetic and mechanistic analysis of oxidation of 2-furoic hydrazide by hexachloroirradate(IV) in a wide pH range

Yao

Tian

et al. 2019

Transit Met Chem

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Oxidations of hydrazine and substituted hydrazines by hexachloroiridate(IV) in aqueous solution: Kinetic and mechanistic analyses

Cited by 19 publications

References 48 publications

Oxidations of Benzhydrazide and Phenylacetic Hydrazide by Hexachloroiridate(IV): Reaction Mechanism and Structure–Reactivity Relationship

Oxidations of Benzhydrazide and Phenylacetic Hydrazide by Hexachloroiridate(IV): Reaction Mechanism and Structure–Reactivity Relationship

New kinetic and mechanistic findings in the oxidation of hydroxylamine by Cerium(IV) in perchloric acid media

Kinetic and mechanistic analysis of oxidation of 2-furoic hydrazide by hexachloroirradate(IV) in a wide pH range

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