An experiment exploring the photochemical properties of quinones was developed. Their unique photochemistry and highly reactive nature make them an ideal class of compounds for examining structure-activity relationships. For several substituted quinones, photochemical reactivity was related to structure and ultimately to the Gibbs energy for electron transfer from water to the quinone. Following irradiation with monochromatic light from a laser pointer and quantification by high-performance liquid chromatography with fluorescence detection, a linear relationship was observed for product formation versus calculated Gibbs energy values. (Contains 1 table, 1 figure and 1 scheme.)