Quantum mechanical calculations have previously shown that certain second-generation alkoxy radicals formed in the atmospheric degradation of isoprene (2-methyl-1,3-butadiene) will undergo a novel reaction pathway: the simultaneous jumping of two H-atoms across the hydrogen bonds with a barrier of only similar to5 kcal/mol. The alkenoxy radical products of these double H-atom transfers are formed with similar to20-25 kcal/mol of energy, and may promptly decompose in competition with quenching to thermal energies. The fate of the energized alkenoxy radicals was determined under atmospheric and common laboratory conditions with use of stochastic Master equation analyses with relative energies determined at the B3LYP/6-311G(2df,2p) level of theory. The analyses accounted for the differing stabilities of, and interconversions between, conformers of the alkenoxy radicals with different numbers and arrangements of hydrogen bonds. Atmospheric implications of the double H-atom transfer are discussed.