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|Title:||I. The Catalytic Oxidation of Olefins by a Cobalt Complex. Ii. The Thermodynamics of Base Binding to a Cobalt Complex (Cosmdpt)|
|Author(s):||Hamilton, Dorothy Ellen|
|Department / Program:||Chemistry|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||Oxidations are key steps in the industrial synthesis of most compounds made. Therefore understanding the mechanisms by which these types of reactions occur is important not only synthetically but also commercially. In many cases transition metal catalysts are used to improve the rate and/or selectivity of such oxidations. Many homogeneous oxidations catalyzed by transition metal complexes, especially those containing first row transition metals, proceed by autoxidation. Since this is a free radical chain reaction the reaction generally is not selective and a variety of products are formed. In chapter I of this thesis is reported a mechanistic study of the oxidation of olefins by cobalt bis(salicylidene-(gamma)-iminopropyl)methylamine, abbreviated CoSMDPT, to selectively form ketones and alcohols. This product selectivity and other studies indicate that common autoxidation is not occurring in this system. A Wacker-type pathway (using water) and the involvement of peracids were also ruled out. Instead a mechanism is proposed which involves the formation of a cobalt hydroperoxide from CoSMDPT and hydrogen peroxide formed in situ by oxidation of the alcohol solvent. Addition of the cobalt hydroperoxide across the olefin double bond leads to an alkyl hydroperoxide which is subsequently decomposed by the Haber-Weiss mechanism to yield the ketone and alcohol products. Deactivation of the catalyst occurs during the reaction due to oxidation of the SMDPT ligand as well as formation of a (mu)-peroxocobalt dimer.
In chapter II of this thesis the binding of bases to another cobalt complex was studied. This complex, abbreviated Co(4,6-CH(,3)Osal-4-CF(,3)oph), was formed by condensing 4,6-dimethoxysalicylaldehyde with 3,4-diaminobenzotrifluoride in the presence of cobalt acetate. The equilibrium constants for binding of dimethylthioformamide, pyridine, tetrahydrofuran, and dimethylsulfoxide were obtained as a function of temperature in order to determine (DELTA)H and (DELTA)S of binding for each base. These results were then compared to earlier results obtained for this system and to results obtained for base binding to a cobalt porphyrin. Based on these comparisons the conclusion was reached that the cobalt complex existed as dimers or oligomers in solution prior to complexation by a base.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1985.
|Date Available in IDEALS:||2014-12-15|