Author

Amro

Date of Award

4-1997

Degree Name

Master of Arts

Department

Chemistry

First Advisor

Dr. Donald R. Schreiber

Second Advisor

Dr. James Howell

Third Advisor

Dr. Ralph Steinhaus

Access Setting

Masters Thesis-Open Access

Abstract

The coordination chemistry of protocatechuic acid and catechols with the first row of transition metals was studied as a model for the more complicated natural humic substance.

The reaction between Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+ and the phenols, catechol and protocatechuic acid in aqueous solution was studied by the spectrophotometric method. The composition of the complexes formed was determined by continuous variation, iso-molar series and molar ratio methods. The presence of complexes with metal:ligand ratio of 1:1, 1:2 and 1:3 was established in the pH range 3 to 11. The consecutive stability constants of the complexes formed at the conditions of complexation was calculated by pH and continuous variations methods.

Thermodynamic quantities were determined by microcalorimetric method, and the values of ∆H for formation of 1:1 metal complexes of catechol and protocatechuic acid were calculated at 25±0.005°C.

This investigation demonstrated that the presence of an electron-withdrawing group had an effect on the heat of complexation. The presence of an electron-withdrawing group decrease the energy liberated during complexation.

The enthalpies of complexation of catechol were used to predict the ligand field stabilization energies on the partially filled d-orbital of the metal ions, and as a model for the determination of AH's of other aromatic ligand similar to catechol.

Included in

Chemistry Commons

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