| Abstract
| - The mechanism of the oxidation of primary and secondary alcohols by the oxoammonium cation derivedfrom 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) has been investigated computationally at the B3LYP/6-31+G* level, along with free energies of solvation, using a reaction field model. In basic solution, thereaction involves formation of a complex between the alkoxide anion and the oxoammonium cation ina pre-oxidation equilibrium wherein methoxide leads to a much larger formation constant than isopropoxide.The differences in free energy of activation for the rate-determining hydrogen transfer within the pre-oxidation complexes were small; the differences in complex formation constants lead to a larger rate ofreaction for the primary alcohol, as is observed experimentally. In acidic solution, rate-determininghydrogen atom transfer from the alcohol to the oxoammonium cation had a large unfavorable free energychange and would proceed more slowly than is observed. A more likely path involves a hydride transferthat would be more rapid with a secondary alcohol than primary, as is observed. Transition states for thisprocess were located.
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