Effects of alkyltrimethylammonium bromide surfactants on the kinetics of the oxidation of tris(1,10-phenanthroline)iron(II) by azido-pentacyanocobaltate(III) complex |
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| Authors: | Grace Olufunmilayo Ogunlusi Olayinka A Oyetunji Olanrewaju Owoyomi Jide Ige |
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| Institution: | 1. Department of Chemistry, Obafemi Awolowo University, Ile-Ife, Nigeriaroogunlusi2003@yahoo.co.uk;3. Department of Chemistry, University of Botswana, Gaborone, Botswana;4. Department of Chemistry, Obafemi Awolowo University, Ile-Ife, Nigeria |
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| Abstract: | The redox reaction between tris(1,10-phenanthroline)iron(II), Fe(phen)3]2+, and azido-pentacyanocobaltate(III), Co(CN)5N3]3? was investigated in three cationic surfactants: dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB) and cetyltrimethylammonium bromide (CTAB) in the presence of 0.1?M NaCl at 35°C. Second-order rate constant in the absence and presence of surfactant, kw and kψ, respectively, were obtained in the concentration ranges DTAB?=?0???4.667?×?10?4?mol?dm?3, TTAB?=?0–9.364?×?10?5?mol?dm?3, CTAB?=?0???6.220?×?10?5?mol?dm?3. Electron transfer rate was inhibited by the surfactants with premicelllar activity. Inhibition factors, kw/kψ followed the trend CTAB?>?TTAB?>?DTAB with respect to the surfactant concentrations used. The magnitudes of the binding constants obtained suggest significant electrostatic and hydrophobic interactions. Activation parameters ΔH≠, ΔS≠, and Ea have larger positive values in the presence of surfactants than in surfactant-free medium. The electron transfer is proposed to proceed via outer-sphere mechanism in the presence of the surfactants. |
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| Keywords: | Electron transfer inhibition outer-sphere mechanism premicellar activity surfactant |
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