Related Experiment Video
Updated: May 5, 2026

Photoelectron Imaging of Anions Illustrated by 310 Nm Detachment of F−
Published on: July 27, 2018
Physicochemical study of a metastable-state photoacid
Valentine K Johns1, Zhuozhi Wang, Xinxue Li
1Department of Chemistry, Eastern Kentucky University , Richmond, Kentucky 40475, United States.
Abstract:
A photoacid that possesses a metastable acidic state induced by visible light is studied. Previous work showed that this photoacid can reversibly produce a large pH change capable of controlling chemical reactions, altering material properties, and killing bacteria. In this work, we studied the relaxation kinetics of the metastable acidic state in different solvents including water, ethanol, and DMSO. In all of these solvents, the kinetic data can be fitted well to a second-order rate equation, which indicates that protonation is involved in the rate-limiting step. The rate constants in water, ethanol, and DMSO are 73, 1.6, and 0.034 M(-1) s(-1), respectively. The slow relaxation in DMSO allowed us to fully characterize the structure of the metastable acidic state using proton NMR. We also measured the quantum yield of the photoreaction, which is as high as 0.37.
Related Concept Videos
Photochemical Electrocyclic Reactions: Stereochemistry
Selection Rules: Photochemical Activation
Deactivation Processes: Jablonski Diagram
Weak Acid Solutions
IR and UV–Vis Spectroscopy of Carboxylic Acids
However, the stretching absorptions for the C=O bond vary depending on the structure of carboxylic acids. The C=O bond of the free carboxylic acids shows a higher stretching frequency, 1760 cm−1, while H-bonded carboxylic acids (dimers) exhibit stretching absorptions at a lower frequency,...
Mass Spectrometry: Carboxylic Acid, Ester, and Amide Fragmentation
For example,...
Chemical Ionization (CI) Mass Spectrometry

