Chemical reaction, Conditions and laws of

The synthesis and reactivity of Nucleophile Assisting Leaving Groups was studied in order to assess the rate enhancement of nucleophilic substitution reactions. Various Nucleophile Assisting leaving groups were synthesized, all of them containing a coordinating arm positioned ortho to an electrophilic center on a benzene ring. The various coordinating arms had novel geometries and binding properties. Their reactivity was studied with a variety of metal salts and the kinetics of the reactions was studied with 1H-NMR spectroscopy. This method provided a quantitative measurement of the rate enhancement observed in the substitution reactions from the rate constants obtained. In the case of certain crown ether-containing substrates, NMR experiments suggest that the mechanism of substitution proceeds in two steps, the first being a pre-coordination of the metal salt with the coordinating arm, followed by a conversion of the complex to products.

Most living organisms utilize electron transport chains in order to obtain energy. Riboflavin, commonly known as vitamin B2, is the central component of the redox coenzymes flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN). These cofactors serve as a prosthetic group to flavoproteins and function as the energy-carrying molecules in electron transfer reactions. In this study, the different ionization and oxidation states of riboflavin were identified and quantified as a function of solution potential and pH. To accomplish this task, spectroelectrochemical reductions of riboflavin at different pH were performed. Spectroscopic data offer clues concerning the identity of underlying species, such as oxidation/ionization states and the controlling equilibria. The large data sets obtained from these experiments were analyzed and the acid dissociation constant for reduced riboflavin was determined.