## University of the Pacific Theses and Dissertations

#### Campus Access Only

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1994

#### Document Type

Dissertation - Pacific Access Restricted

#### Degree Name

Doctor of Philosophy (Ph.D.)

Chemistry

Silvio Rodriguez

Richard Dodge

Patrick Jones

Larry Spreer

#### Fourth Committee Member

Ravindra Vasavada

#### Abstract

Kinetic studies, as well as the thermodynamics of the formation of the Cu(II)-Pyridine-2-azo-p-dimethylaniline complex ion in aqueous solutions, and in the presence of sodium dodecyl sulfate (SDS) are reported. The kinetic determinations of the formation of complex were performed using the temperature jump technique. The rate constants in the forward (k$\rm \sb{f}$) and backward (k$\rm\sb{b}$) directions had values of (2.10 $\pm$ 0.97) $\times\ 10\sp7$ scM$\rm \sp{-1}s\sp{-1}$ and (10.0 $\pm$ 0.35) $\rm \times\ 10\sp{2}\ \sb{s}\sp{-1}$ respectively in aqueous solution at 25$\sp\circ$C. The numerical values of the rate constants were analyzed satisfactorily according to the Eigen-Wilkins mechanism. The rate of the reaction was determined at different concentrations of SDS. Different effects on the rate of the reaction were observed as the concentration of SDS was changed. The rate of the reaction was enhanced as the concentration of SDS was increased, reaching a maximum at the critical micelle concentration (4.30 $\times$ 10$\sp{-3}$ M SDS), and decreasing slowly as the concentration of SDS became larger than the c.m.c. The kinetic results above the critical micelle concentration were successfully interpreted in terms of the Berezin model. These results indicate that the enhancement observed at the c.m.c. is due to a concentrative effect. The rate coefficient k$\rm \sb{f}$ and k$\rm \sb{b}$ were calculated at two concentrations of SDS. The forward rates of reaction obtained at 25$\sp\circ$C in the presence of SDS are: (3.13 $\pm$ 0.32) $\rm \times\ 10\sp7 M\sp{-1}s\sp{-1}$ at 4.30 $\times$ 10$\sp{-3}$ M SDS and (2.65 $\pm$ 0.21) $\rm \times\ 10\sp7 M\sp{-1}s\sp{-1}$ at 8.82 $\times$ 10$\sp{-3}$ M SDS. The activation enthalpy and entropy for the reaction were also determined at different concentrations of SDS. Both activation parameters showed a minimum at the c.m.c. of the surfactant with a corresponding maximum in the experimental $\rm k\sb{obs}$. Additives such as methyl sulfate and dodecyltrimethylammonium bromide showed no enhancement of the rate of reaction.

182

#### ISBN

9780591420593 , 0591420597

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