Reaction of photochemically generated hot hydrogen atoms with 1-butene

Abstract

The reaction of hot hydrogen atoms with 1-butene was studied in the gas phase at pressures in the range 0.4–400 Torr (0.5–533 hPa). Hydrogen atoms were generated by exposing HI to the action of UV light (λ = 334 and 313 nm). Some of the hydrogen atoms add to the double bond in a first collision yielding highly excited sec-butyl and n-butyl radicals; the remainder undergo thermalization according to a step-ladder model. The evidence that hot hydrogen atom addition occurs is based on kinetic considerations—both experimental and calculated RRKM rate constants for decomposition of the excited butyl radicals are given—and is supported by the observation that the contribution of non-terminal addition of hot hydrogen atoms reaches a level of about 30%, whereas thermal hydrogen atoms add mainly (about 94%) to the terminal carbon atom. The hot hydrogen atom + olefin chemical activation technique provides an interesting tool for the investigation of highly excited radicals.