Photolysis of Aldehydes and Ketones in the Presence of Iodine Vapor

The photolysis of acetone and of formaldehyde takes place principally through a free radical mechanism. The primary processes consist in the splitting off of a methyl radical and a hydrogen atom, respectively. The primary process in the photolysis of methyl ethyl ketone also consists in the splitting off of either a methyl or an ethyl radical. The heat of dissociation of the first hydrogen in formaldehyde is shown to be as low as 78 kcal. Approximately 26 kcal. is required to remove the second hydrogen atom.