Date of Award
Doctor of Philosophy
The decomposition of the unstable alkylcobaloxime, (alpha)-phenylethyl(aquo)cobaloxime, proceeds rapidly in acidic, aqueous methanol leading to the formation of styrene and dimeric organic products. Kinetic studies were carried out at (mu) = 1.0 M in the H('+) range 0.0014 - 1.0 M. The results obeyed the rate expression -dC(,6)H(,5)CH(CH(,3))Co(dmgH)(,2)(OH(,2))/dt = (k(,b) + k(,a)K(,H)H('+)/1 + K(,H)H('+)) with k(,b) = (3.27 (+OR-) 0.21) x 10('-3) s('-1), k(,a) = (1.48 (+OR-) 0.14) x 10('-2) s('-1), and K(,H) = 8.13 (+OR-) 0.38 M('-1) at 25.0(DEGREES)C. Activation parameters have been evaluated for k(,b) and k(,a). The rate of decomposition of (alpha)-phenylethyl(aquo)cobaloxime is independent of added oxidants, such as H(,2)O(,2) and Co(NH(,3))(,5)Br('2+). A mass law retardation effect is observed in the presence of Co(en)(,3)('3+) in neutral solution. The kinetic and product analysis data are used to show that decomposition of (alpha)-phenylethyl(aquo)cobaloxime involves concurrent homolytic and (beta)-elimination pathways in acidic media;Vitamin B(,12s) has been generated electrochemically at pH 2.5-3.2in aqueous glycine buffers to yield reasonably stable solutions understrictly oxygen-free conditions. The reaction of B(,12s) and a series ofchromium(III) complexes, (H(,2)O)(,5)CrX('2+) with X = F('-), Cl('-), Br('-), N(,3)('-),NCS('-), SH('-), and OH('-), occurs rapidly to produce B(,12r) and Cr('2+). Thekinetic results follow a second-order rate expression -dB(,12s)/dt =k(,x)B(,12s)CrX('2+). Electron transfer is proposed to occur by an inner-;sphere mechanism;('1)DOE Report IS-T-964. This work was performed under ContractW-7405-Eng-82 with the Department of Energy.
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Helen Broom Gjerde
Gjerde, Helen Broom, "Kinetic studies of organocobalt compounds related to vitamin B12 coenzymes " (1981). Retrospective Theses and Dissertations. 7421.