The Ultraviolet Absorption Spectra of Gaseous Diazomethane and Diazoethane. Evidence for the Existence of Ethylidine Radicals in Diazoethane Photolysis

The absorption of gaseous diazoethane begins at about 5400A, increases to a broad maximum of ε=3.5 at 4500A and falls to a minimum of ε=0.15 at 3200A. At wavelengths shorter than 3000A a second region of rapidly increasing absorption is found. The absorption curve of diazomethane is similar in general shape to this curve but shifted somewhat toward shorter wavelengths. The absorption of diazoethane is continuous over its entire region while in the visible region diazomethane shows a number of broad and very diffuse bands from about 4300A to 3200A which probably overlie a continuum. The presence of 2‐butene in the photolysis products of diazoethane is explained by the combination of ethylidine radicals formed by the primary photochemical process $${\mathrm{CH}}_3{\mathrm{CHN}}_2\mathrm{+h\nu \to }{\mathrm{CH}}_3\mathrm{CH}+{\mathrm{N}}_2.$$