The objective of this project is the development of a new method based on carbon-13 nuclear magnetic resonance chemical shifts for determining thermodynamic acidity functions for liquid and solid acids. Medium effects are eliminated by using the difference in chemical shift between two carbon atoms in the same molecule as the measurement parameter. The new method is applicable to systems lacking the transparency to visible and ultraviolet light required for use of traditional Hammett indicators, and is extendable to solids. To relate solid acidity to solution acidity, the protonation equilibrium of indicator bases in solution is studied at the stoichiometric acid-to-base ratio and the same indicator bases are then studied on solid acids at equimolar ratios of base to acid sites. Finally, the effects of solvents on acid strengths is examined. Although the concept of acidity is often used to interpret the effects of solid catalysts, there is, in fact, no sound technique to measure or quantify this property for solids. This project addresses this problem directly; success would provide a more rational framework for understanding of many catalytic systems, and also of corrosion, composite stability, and chromophoric displays.
