Generally used to describe a chemical reaction caused by absorption of ultraviolet, visible or infrared radiation. There are many ground-state reactions, which have photochemical counterparts. Among these are photochemical nitrogen extrusions, photocycloadditions, photodecarbonylations, photodecarboxylations, photoenolizations, photo-Fries rearrangement, photoisomerizations, photooxidations, photorearrangements, photoreductions, photosubstitutions, etc.
Photochemical paths offer the advantage over thermal methods of forming thermodynamically disfavoured products, overcome large @A00093@ barriers in a short period of time, and allow reactivity otherwise inaccessible by thermal methods.
PAC, 2007, 79, 293. 'Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)' on page 386 (https://doi.org/10.1351/pac200779030293)