Date of Graduation

1978

Document Type

Dissertation

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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