Transition Metal Chemistry p. 771 - 777 (2019)
Update date:2022-08-11
Topics:
Yao, Haiping
Tian, Hongwu
Xu, Liyao
Xia, Yanqing
Zhou, Li
Liu, Chunli
Shi, Tiesheng
Oxidation of 2-furoic hydrazide (FH) by hexachloroiridate(IV) ([IrCl6]2?) was studied kinetically in a wide pH range in aqueous solution of 1.0?M ionic strength. The oxidation reaction followed well-defined second-order kinetics: ? d[IrCl6 2?]/dt = k′[FH]tot[IrCl6 2?], where [FH]tot denotes the total concentration of FH and k′ stands for the observed second-order rate constants. The established k′–pH profile displays that k′ increases drastically with pH and a plateau region exists between pH 4 and 6. A stoichiometric ratio of Δ[FH]tot/Δ[IrCl6 2?] = 1/4?was revealed by spectrophotometric titrations. 1H NMR spectroscopic studies indicated that FH was cleanly oxidized to 2-furoic acid. The kinetic data suggest a reaction mechanism in which all the three protolysis species of FH react with [IrCl6]2? in parallel, forming the rate-determining steps. Two stabilized hydrazyl radicals are generated in the rate-determining steps, in which a single electron is transferred to [IrCl6]2?. The two hydrazyl radicals react rapidly in consecutive steps requiring 3?mol of Ir(IV) to form 2-furoic acid as the final product. Rate constants of the rate-determining steps were deduced through a simulation of the rate expression to the k′–pH dependency data. Values of these rate constants demonstrate that the three protolysis species of FH have a huge reactivity span, changing by about 109 times toward reduction in [IrCl6]2? and that FH can be readily oxidized in neutral and basic media. Rapid scan spectra and the measured activation parameters suggest that an outer-sphere electron transfer is probably taking place in each of the rate-determining steps. This is the first kinetic study on the oxidation reactions of FH and provides concurrently the protolysis constants of FH (pKa1 = 3.04 ± 0.08 and pKa2 = 11.6 ± 0.1) at 25.0?°C and 1.0?M ionic strength.
View MoreZhejiang Hoshine Silicon Industry Co., Ltd.
Contact:86-573-89179966
Address:Zhapu Town, Pinghu City, Zhejiang, China
Xinxiang Hongqi District Houyuan Trading Co., Ltd
Contact:86-373-3695376
Address:Xinxiang City, Henan Province, China
Shanghai Dynamic Industrial Co.,Ltd.
website:http://www.shdynamic.com
Contact:86-021 3392 6680
Address:Room 805 Information Tower, No.1403 Minsheng Road, Pudong New Area, Shanghai 200135, P. R. China
Suzhou Jingye Medicine & Chemical Co., Ltd
website:http://www.jingyechem.cn
Contact:+86-512-66658588
Address:No. 88, Sanlian Street, Jinfeng Road, Suzhou New District, Jiangsu Province, P. R. China
website:http://www.sigmaaldrich.com
Contact:800 558-9160
Address:Industriestrasse 25CH-9471 Buchs SGSwitzerland
Doi:10.1007/BF00854611
()Doi:10.1246/bcsj.53.458
(1980)Doi:10.1016/S0968-0896(02)00126-8
(2002)Doi:10.1016/j.poly.2010.08.033
(2010)Doi:10.1039/c7ob00616k
(2017)Doi:10.1021/om200998d
(2012)