Date of Graduation

1978

Document Type

Dissertation/Thesis

Abstract

The application of hydrodynamic voltammetry to the study of heterogeneous electron transfer rate constants on platinum and graphite, and homogeneous rate constants for a chemical step coupled with charge transfer reaction(s) is presented. Turbulent flow forced convection at the vibrating electrode was used to determine the kinetic parameters for the reduction of Ce^+ 3+ 7 and Fe in 1 M H^SO^ and 0.1 M HCIO^ on platinum, and of Fe(CN)^-, 4+ 3+ Ce , and Fe in various background media on wax-impregnated graphite. Similar redox systems were found generally to have slower rates on graphite than on platinum. An exception, the electron transfer rate of Ce^+ did not change significantly when the electrode material was changed from platinum to graphite. The rate constants at wax-impregnated graphite were similar to those reported for carbon paste. Cavitation at the vibrating electrode at linear velocities greater than 18 cm/sec limited the magnitude of mass transfer attainable to 0.005 cm/sec. Due to this limitation, electron transfer rate constants larger than 0.01 cm/sec cannot be measured with acceptable precision using the vibrating electrode. A hydrodynamic system was satisfactorily designed and used to study the kinetics of homogeneous chemical reactions in ECE (charge transfer - chemical step - charge transfer) and EC (charge transfer - chemical step) mechanisms. The chemical rate constant for the dehydration of o-hydroxylaminophenol, the coupled reaction in the reduction of o-nitrophenol (ECE), was evaluated using a packed graphite flow-through cell as a generating electrode and a vibrating electrode 2 as a sensing electrode to monitor the course of the chemical reaction. The chemical rate constant for the hydrolysis of benzoquinoneimine which follows the oxidation of p-aminophenol (EC) was studied using an improved modification of the electrolysis cell used in the ECE study.

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