Illuminating Reactions - a Photoredox Catalysis Experiment for Undergraduate Students

A teaching experiment in photoredox catalysis has been developed for the third year undergraduate laboratory, drawing together different aspects of practical chemistry including synthesis, photophysical measurements, and computational studies to enable students to understand key concepts. In the experiment, an organic dye, 9-mesityl-10-methylacridinium tetrafluoroborate, is used as a catalyst for the anti-Markovnikov addition of acetic acid to trans-anethole under blue light. Over 3–4 lab periods of 6 h each, students carry out the reaction and purification and use ¹H NMR, ¹³C NMR and infrared spectroscopy to characterize the product and confirm the regioselectivity of the reaction. They use results from DFT calculations using Gaussian16 to explain the regioselectivity. They measure physical properties of the dye by UV–vis absorption spectroscopy, fluorescence spectroscopy and cyclic voltammetry to estimate the redox potential of the dye in its excited state, and use this to explain its ability to catalyze an oxidation step in the presence of light. Results from assessment showed a high level of achievement of the learning objectives, with students demonstrating the ability to combine different experimental methods to build an understanding of a field of chemistry which is new to them.