KINETICS AND MECHANISMS OF THE ELECTRON TRANSFER REACTIONS OF DIAQUOTETRAKIS (2, 2’- BIPYRIDINE)-μ-OXODIRUTHENIUM(III) IONS AND SOME REDUCTANTS IN AQUEOUS MEDIUM

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dc.contributor.authorMOHAMMED, Yahaya
dc.date.accessioned2016-07-28T08:44:25Z
dc.date.available2016-07-28T08:44:25Z
dc.date.issued2015-10
dc.descriptionA THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES, AHMADU BELLO UNIVERSITY ZARIA, IN PARTIAL FULFILLMENT FOR THE AWARD OF Ph.D. INORGANIC CHEMISTRY DEPARTMENT OF CHEMISTRY AHMADU BELLO UNIVERSITY ZARIAen_US
dc.description.abstractThe kinetics and mechanisms of the electron transfer reactions of diaquotetrakis (2, 2’- bipyridine)-μ-oxodiruthenium(III) ions (hereafter denoted as Ru2O4+or [(H2O)2Ru2O]4+ ) and thiourea (TU),N–methylthiourea (MTU), N–allylthiourea (ATU), N,N’- dimethylthiourea(DMTU) (collectively denoted by TSH), thiosulphate ions (S2O3 2–), dithionite ions (S2O4 2–), hypophosphorous acid (H3PO2), methanol (CH3OH), ethanol (C2H5OH) and propanol (C3H7OH) (collectively denoted as ROH) were studied in aqueous perchloric acid (HClO4) medium (except for S2O4 2– and the alcohols) at I = 0.5 mol dm–3 and T = (31.0 ± 1) °C. The stoichiometry was found to be 1:2 (Ru2O4+/ reductant) in the TSH and S2O3 2–systems but 1:1 in the S2O4 2–, H3PO2 and ROH systems. The rate of reaction is first order in oxidants and reductants for all the systems. Addition of acid has inverse effect on the rates of reaction for the TSH system, but direct dependence for the S2O3 2– system. The overall rate equation for the TSH reaction can be given as : - [Ru2O4+] = (a + b[H+]-1 )[Ru2O4+][Reductant] . while that for S2O3 2– reaction can be given as: - [Ru2O4+] = (a + b[H+])[Ru2O4+][S2O3 2-] Varying the ionic strength (I) and dielectric constant (D)of the reaction medium had no effect on rates of reaction for the TSH, S2O4 2-, H3PO2 and ROH reactions, while for the S2O3 2– reaction, increase in I led to a decrease in rate while decrease in D led to increase in rate of reaction. Added ions had no effect on the TSH and H3PO2 reactions but led to vii catalysis and/ or inhibition in S2O32–, S2O42- and ROH systems. Free radicals were identified in the TSH, H3PO2 and ROH reactions only. Spectroscopic information and the results of the Michaelis – Menten plots suggest the lack of formation of intermediate complex prior to electron transfer for all the systems. For all the reactions, [(H2O)2(bipy)2Ru]2+ was found to be the product of Ru2O4+ reduction. For the TSH reaction, disulphides was found to be the oxidation product of TSH while, for H3PO2 reaction, test for phosphorous acid (H3PO3) presence was positive and for the ROH system, test for aldehydes was also positive. The order of reactivity for the TSH system is ATU > DMTU > MTU > TU, while the order of reactivity for the sulphur oxyanions’ reactions is S2O42-> S2O32– and that for the ROH reactions is CH3OH > C2H5OH > C3H7OH. Based on the Michaelis–Menten plots and the interactions with added ions, all the reactions are proposed to have proceeded through the outer–sphere electron transfer mechanism. Plausible mechanisms for all the reactions have been proposeden_US
dc.identifier.urihttp://hdl.handle.net/123456789/8230
dc.language.isoenen_US
dc.subjectKINETICS AND MECHANISMS,en_US
dc.subjectELECTRON TRANSFER REACTION,en_US
dc.subjectDIAQUOTETRAKIS,en_US
dc.subject(2, 2’- BIPYRIDINE)-μ-OXODIRUTHENIUM(III),en_US
dc.subjectIONS,en_US
dc.subjectREDUCTANTS,en_US
dc.subjectAQUEOUS MEDIUMen_US
dc.titleKINETICS AND MECHANISMS OF THE ELECTRON TRANSFER REACTIONS OF DIAQUOTETRAKIS (2, 2’- BIPYRIDINE)-μ-OXODIRUTHENIUM(III) IONS AND SOME REDUCTANTS IN AQUEOUS MEDIUMen_US
dc.typeThesisen_US
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