Abstract

A current, longstanding undergraduate physical chemistry kinetics experiment uses UV-Vis spectrophotometry to follow the hydrolysis of para-nitrophenyl acetate (NPA) with an imidazole (Im) catalyst. The catalyzed and uncatalyzed reaction paths can be studied simultaneously under pseudo first order conditions ([Im]>>>[NPA]). To obtain the rate constants for the catalyzed and uncatalyzed reactions, the concentration of imidazole is varied between reactions and then plotted against the observed rate constant (kobs).This produces a linear line where the slope is equal to the rate constant of the catalyzed reaction (kcat) and the intercept is equal to the rate constant of the uncatalyzed reaction (k0). Further studies that vary temperature are performed to relate kinetic data to the thermodynamic parameters at the transition state.

Since not all institutions of higher learning have research opportunities or sufficient funding for specialized equipment, it is valuable to have laboratory courses whose experiments are cost-effective, easily repeatable, and teach a range of chemical topics. This project seeks to redesign the longstanding ester hydrolysis experiment to also study how steric hindrance, electronic factors, and base strength effect the rates of the reaction. To undertake this, a series of nitrophenyl ester analogues that have increasing steric hindrance and increasing electronegative elements was synthesized. Following synthesis, purification, and characterization, each new analogue was tested with the original experimental parameters to obtain kinetic data. Adaptations to the original parameters were determined for each analogue to ensure data was attainable and repeatable.

Date of publication

4-2026

Document Type

Thesis

Language

english

Persistent identifier

http://hdl.handle.net/10950/5044

Committee members

Sean Butler, Ph.D., Rachel Mason, Ph.D., Bryan Tuten, Ph.D.

Degree

Master of Science in Chemistry

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