radicals to a substituted cyclobutane (the Norrish–Yang reaction). Scope The Norrish reaction has been studied in relation to environmental chemistry with respect to the photolysis of the aldehyde heptanal, a prominent compound in Earth's atmosphere. Photolysis of heptanal in conditions resembling atmospheric conditions results in the formation of 1-pentene and acetaldehyde in 62% chemical yield together with cyclic alcohols (cyclobutanols and cyclopentanols) both from a Norrish type II channel and around 10% yield of hexanal from a Norrish type I channel (the initially formed n-hexyl radical attacked by oxygen). In one study the photolysis of an Acyloin derivative in water in presence of hydrogen tetrachloroaurate (HAuCl4) generated nanogold particles with 10 nanometer diameter. The species believed to responsible for reducing Au3+ to Au0 is the Norrish generated ketyl radical. Paquette's 1982 synthesis of dodecahedrane involves three separate Norrish-type reactions in its approximately 29-step sequence. An example of a synthetically useful Norrish type II reaction can be found early in the total synthesis of the biologically active cardenolide ouabagenin by Baran and coworkers. The optimized conditions minimize side reactions, such as the competing Norrish type I pathway, and furnish the desired intermediate in good yield on a multi-gram scale. See also Photo-Fries rearrangement - a related reaction of aromatic carbonyls McLafferty rearrangement - similar to a Type II Norrish reaction. Caused by electron impact ionization rather than light Carbon monoxide-releasing molecules References Free radical reactions Photochemistry Name reactions