标题:Oxidations of benzhydrazide and phenylacetic hydrazide by hexachloroiridate(IV): Reaction mechanism and structure–reactivity relationship
作者:Zhang X.
作者机构:[Zhang, X] College of Chemistry and Chemical Engineering, Shandong University, Jinan, 250014, China
通讯作者:Zhang, X(zhangxlai@sdu.edu.cn)
通讯作者地址:[Zhang, X] College of Chemistry and Chemical Engineering, Shandong UniversityChina;
来源:Molecules
出版年:2020
卷:25
期:2
DOI:10.3390/molecules25020308
关键词:Benzhydrazide; Hexachloroirridate(IV); Oxidation; Phenylacetic hydrazide; Reaction mechanism; Structure–reactivity relationship
摘要: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 k0 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. © 2020 by the author.
收录类别:SCOPUS
资源类型:期刊论文
原文链接:https://www.scopus.com/inward/record.uri?eid=2-s2.0-85077941523&doi=10.3390%2fmolecules25020308&partnerID=40&md5=a216971b2e0edfbdde0e15ddfdaf3967
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