Hydrogen atom release from methyl groups of energized molecules

Abstract

Articles you may be interested inUltraviolet photochemistry of buta-1,3-and buta-1,2-dienes: Laser spectroscopic absolute hydrogen atom quantum yield and translational energy distribution measurements Site and isotope effects on the molecular hydrogen elimination from ethylene at 157 nm excitation Differential cross section polarization moments: Location of the D-atom transfer in the transition-state region for the reactions Cl+C 2 D 6 →DCl (v ′ =0,J ′ =1)+ C 2 D 5 and Cl+CD 4 →DCl (v ′ =0,J ′ =1)+ CD 3 Three diverse molecules, 2,3,4,5,6-pentafluorotoluene ͑PFT͒, trimethylamine ͑TMA͒, and methyl bromide were irradiated by weak 193.3 nm light. In each case hydrogen atoms were released, as the major channel for PFT and as a minor channel for the two others. The low average translational energy release, the isotropic angular distribution, and the linear excimer power dependence all lead to the conclusion that the dissociation is from a very hot ground state. The unimolecular dissociation is less selective than in the more usual unimolecular processes at much lower energies. During these experiments an unusual multiphoton dissociation was found. Focusing 205.1 nm light on TMA produces H atoms with an average kinetic energy of 4.2Ϯ0.5 eV.

Dissociation rate of hot benzene

“…[13][14][15][16][17][18][19] However, the simplest and the most important aromatic compound, benzene, has a much slower dissociation rate and the accurate measurement has not been carried out yet. Here we report the dissociation rate of hot benzene produced by the 193 and 248 nm excitation under the collision-free condition.…”

The photochemistry of 1,4-cyclohexadiene in solution and in the gas phase: conical intersections and the origin of the ‘helicopter-type’ motion of H2 photo-generated in the isolated molecule

“…5, the H atom that migrates on the way to a conical intersection is driven a long way from the heavy atoms skeleton, and under collision free conditions is likely to dissociate. H-atom elimination is favored from the entropy point of view, and is a ubiquitous process 31 observed upon UV irradiation of many organic molecules in the gas phase. The reaction takes place indirectly, in the sense that the C-H chromophore need not absorb the photolyzing radiation.…”

“…The reaction takes place indirectly, in the sense that the C-H chromophore need not absorb the photolyzing radiation. It was determined that the dissociation often took place from a very hot ground state; 31 this indicates a rapid internal conversion process. Under the experimental conditions reported in ref.…”

Photodissociation of Benzotrifluoride at 193 nm

“…Since the fluorine atom is not an electronic chromophore in 200−250 nm, the dissociation mechanism in this photon energy region is similar to the alkyl-substituted benzenes. H atom elimination has been observed from the 193 nm excitation of 2,3,4,5,6-pentafluorotoluene, and a dissociation rate (an overall disappearance rate of pentafluorotoluene) of 8.5 × 10 5 s -1 was obtained . Photodissociation of benzotrifluoride at 193 nm has been previously studied .…”

“…The ultraviolet photochemistry of aromatic compounds and their related molecules has been the subject of many recent studies. − UV absorption of the phenyl halides corresponds to the excitations of electrons of the phenyl ring and the nonbonding electron of the halogen atoms. The nonbonding electron excitation of the halogen atoms leads to direct dissociation, that is, an immediate release of halogen atoms on a repulsive surface.…”