Date of Award
Master of Arts
Dr. Donald R. Schreiber
Dr. James Howell
Dr. Ralph Steinhaus
Masters Thesis-Open Access
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.
Amro, "Thermal Studies of Complex Formations of First Row Transition Metals with Phenolic Compounds in Aqueous Solution" (1997). Master's Theses. 4351.