Senior Honors Projects, 2010-current

Date of Award

Spring 2014

Document Type

Thesis

Degree Name

Bachelor of Science (BS)

Department

Department of Chemistry and Biochemistry

Advisor(s)

Yanjie Zhang

Gina MacDonald

Kevin Caran

Abstract

The Hofmeister series, discovered in 1888, originally ranked ions in correspondence to their relative effects on protein solubility. The series has shown stunning consistency for the relative effects of specific ions on physical phenomena that occur in aqueous solution. Protein denaturation, micelle formation, and surface tension comprise some of the aqueous processes of significance for Hofmeister ion discoveries. Despite significant research efforts confirming series’ ranking, the mechanisms that explain the observed effects are not well understood. This research project herein investigates the specific anion effects on the thermodynamics of caffeine partition between aqueous and cyclohexane phases. The Gibbs free energy, enthalpy, and entropy for caffeine partition are determined in the presence of 11 sodium salts in the aqueous phase. Correlations between thermodynamic data and anion physical properties provide insights into the mechanisms through which anions interact with caffeine and further affect caffeine distribution between two phases. Application of the mechanisms describing the modulation of caffeine partition by anions may help explain Hofmeister anion effects on a variety of behaviors in aqueous solution.

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