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Doctor of Philosophy




The kinetics and mechanisms of the reactions of nitrous acid with pentaaquoorganochromium(III) complexes were studied. Nitrous acid reacts with (H(,2)O)(,5)CrR('2+) complexes via an NO('+) intermediate by either an electrophilic or electron transfer mechanism depending on the nature of the R group. The rate constants for the aliphatic organochromium complexes can be correlated using a linear free energy correlation which implies a common transition state for these reactions. The lack of steric effects for the reactions of the alkyl-chromium complexes, and the detection of Cr('2+) as an intermediate in the reactions of the (alpha)-hydroxy- and (alpha)-alkoxyalkylchromium complexes suggests that these complexes react with HONO by an electron transfer mechanism. A mechanism has been proposed in which NO('+) is formed which then oxidizes CrR('2+) by one electron to give CrR('3+). This species decomposes to Cr('3+) and R(.) when R is an alkyl group, but forms Cr('2+) and ROH when R is an (alpha)-hydroxy- or (alpha)-alkoxyalkyl group. R(.) and Cr('2+) react with the NO formed in the reaction to give RNO and CrNO('2+), respectively;In contrast, aralkylchromium(III) complexes react with nitrous acid by an electrophilic mechanism as indicated by the products and correlations of the rate constants with other electrophilic reactions in the literature;Photochemically generated tris(2,2'-bipyridyl)-ruthenium(III) oxidizes a range of pentaaquoorganochromium(III) complexes by one electron. The trends in the rate constants and the usual behavior of Ru(bpy)(,3)('3+) suggest that electron transfer is occurring by an outer-sphere mechanism. In the case of CrCH(,2)CH(,3)('2+), the intermediate;formed, CrCH(,2)CH(,3)('3+), decays to Cr('3+) and (.)CH(,2)CH(,3) as shown by kinetic studies and a product analysis; ('1)DOE Report IS-T-1193. This work was performed under contract W-7405-Eng-82 with the Department of Energy.



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Jon David Melton



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139 pages