KINETICS AND MECHANISMS OF REDOX REACTIONS OF TETRAKIS(2,2'-BIPYRIDINE)-μ-OXODIIRON(III) COMPLEX AND SOME REDUCTANTS IN AQUEOUS HYDROCHLORIC ACID

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dc.contributor.authorANWETING, IDONGESIT BASSEY
dc.date.accessioned2017-10-17T08:59:28Z
dc.date.available2017-10-17T08:59:28Z
dc.date.issued2016-12
dc.descriptionA THESIS SUBMITTED TO THE SCHOOL OF POSTGRDUATE STUDIES, AHMADU BELLO UNIVERSITY, ZARIA, IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF A DOCTOR OF PHILOSOPHY DEGREE IN INORGANIC CHEMISTRY DEPARTMENT OF CHEMISTRY, FACULTY OF PHYSICAL SCIENCE AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA DECEMBER,en_US
dc.description.abstractThe electron transfer reactions of tetrakis (2, 2'- bipyridine)-μ-oxodiiron(III) complex ion (Fe2O4+) with thiourea (TU), N-methylthiourea (MTU), N–allylthiourea (ATU), N,N’–dimethylthiourea (DMTU), N,N’-dimethylthiourea (DETU), dithionite ion(S2O42–), dithionate ion (S2O62–), semicarbazide (EH2), diphenylcarbazide (DH2) and glutathione (GSH) were studied spectrophotometrically, in aqueous hydrochloric acid medium at T = 27.0 ± 3.0oC, I = 0.3 mol dm-3 (NaCl), [H+] = 1.0 ×10-3 mol dm-3 (HCl) and λmax = 520 nm. The stoichiometry was found to be 1:1(Fe2O4+/reductant) in all other systems but 1:2 in theFe2O4+- GSH system. The reactions of Fe2O4+- thioureas follow identical kinetics, being first order each with respect to [oxidant] and [thiourea] and second order overall. The reaction of Fe2O4+ with dithionite(S2O42-)ion, dithionate(S2O62-) ion, semicarbazide (EH2), diphenylcarbazide (DH2) and glutathione(GSH) follow first order and zero order with respect to oxidant and reductants respectively and first order overall. Changes in hydrogen ion concentration, the dielectric constant and ionic strength of the medium have no considerable influences on the rate in all the systems. The reactions involving thioureas were not affected by addition of cations but there was inhibition of the rate of reaction when anions were added. However, for all other systems the rate of reaction was independent of added cations and anions. Under comparable experimental conditions, the rate of oxidation of the thioureas followed the order k2(TU) < k2(DETU) < k2(ATU) < k2(MTU) < k2(DMTU), sulphur oxyanions kobs(S2O62-) < kobs(S2O42-) and that for the carbazides is kobs(EH2) < kobs(DH2). The observed kinetics in the reactions involving thioureas is in agreement with the rate law. [Fe2O4+] = k2[Fe2O4+][thioureas]. While that for other reductants can be given as: [Fe2O4+] = kobs [Fe2O4+] In all the reactions, Fe2+ was found to be the product of Fe2O4+ reduction. The oxidation products of the reactions of thioureas were urea/urea derivatives and sulphur using both spectroscopic and qualitative methods. Whereas sulphate ion was qualitatively identified in S2O42- and S2O62- reactions, disulphide was identified as the product of the reaction of GSH with Fe2O4+. Spectroscopic evidence and Michaelis-Menten plots did not indicate the formation of intermediate complex prior to electron transfer, there was also absence of free radicals formation in all the systems. Based on the Michaelis- Menten plots, interactions with added ions, all the reactions are proposed to have proceeded through the outer-sphere electron transfer mechanism. Plausible mechanisms have been proposed for all the systemsen_US
dc.identifier.urihttp://hdl.handle.net/123456789/9294
dc.language.isoenen_US
dc.subjectKINETICSen_US
dc.subjectMECHANISMSen_US
dc.subjectREDOX REACTIONSen_US
dc.subjectTETRAKIS(2,2'-BIPYRIDINE)-μ-OXODIIRON(III)en_US
dc.subjectAQUEOUS HYDROCHLORIC ACIDen_US
dc.subjectHYDROCHLORIC ACIDen_US
dc.titleKINETICS AND MECHANISMS OF REDOX REACTIONS OF TETRAKIS(2,2'-BIPYRIDINE)-μ-OXODIIRON(III) COMPLEX AND SOME REDUCTANTS IN AQUEOUS HYDROCHLORIC ACIDen_US
dc.typeThesisen_US
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