Vibrational relaxation of HOD by collisions with Ar atoms.

Vibrational relaxation of HOD(v12, v3) molecules by collisions with Ar was studied at 298 K (v12 denotes coupled bending, v2, and OD stretching, v1, vibrational modes and v3 denotes OH stretching mode). The vibrationally excited HOD molecules were generated by exothermic abstraction reactions of OD radicals with 13 different RH reactants and observed by infrared emission from a fast-flow reactor as a function of Ar pressure and reaction time. State-specific relaxation rate constants were obtained by comparison of the time evolution of the experimental vibrational distributions with numerical kinetic calculations for vibrational populations.

Vibrational relaxation of high levels of HO by collisions with Ar as studied by infrared chemiluminescence.

Vibrational relaxation of HO(v,v) molecules by collisions with Ar was studied at 298 K (v denotes the bending vibrational mode and v denotes the sum of the symmetric, v, and asymmetric, v, vibrational modes). The HO molecules from 14 different exothermic reactions of H-atom abstraction by OH radicals were observed by infrared emission from a fast flow reactor as a function of Ar pressure and reaction time. Numerical kinetic calculations were used to obtain rate constants for stretch-to-bend energy conversion, (v,v) → (v + 2,v - 1), and pure bend relaxation, (v,v) → (v - 1,v).

Unimolecular HBr and HF Elimination Reactions of Vibrationally Excited CHCHBr and CDCHFBr: Identification of the 1,1-HBr Elimination Reaction from CDCHFBr and Search for the CD(F)C:HBr Adduct.

Chemical activation experiments and computational methods have been used to study the unimolecular reactions of CHCHBr and CDCHFBr with 90 and 93 kcal mol of vibrational energy, respectively. The four-centered elimination reactions of HBr and DBr are the dominant reactions; however, 2,1-DF, 1,1-HBr, and 1,1-HF reactions are also observed from CDCHFBr. The main focus was to search for the role of the CD(F)C:HBr adduct in the 1,1-HBr elimination for comparison with carbene adducts in 1,1-HX(Y) elimination from RCHXY (X,Y = Cl and F) molecules.

Experimental and Computational Studies of Unimolecular 1,1-HX (X = F, Cl) Elimination Reactions of CDCHFCl: Role of Carbene:HF and HCl Adducts in the Exit Channel of RCHFCl and RCHCl Reactions.

The gas-phase unimolecular reactions of CDCHFCl molecules with 94 kcal mol of vibrational energy have been studied by the chemical-activation experimental technique and by electronic-structure computations. Products from the reaction of CDCHFCl molecules, formed by the recombination of CD and CHFCl radicals in a room temperature bath gas, were measured by gas chromatography-mass spectrometry. The 2,1-DCl (81%) and 1,1-HCl (17%) elimination reactions are the principal processes, but 2,1-DF and 1,1-HF elimination reactions also are observed.

Analysis of the Five Unimolecular Reaction Pathways of CDClCHFCl with Emphasis on CDCl(F)C: and CDCl(Cl)C: Formed by 1,1-HCl and 1,1-HF Elimination.

The five unimolecular HX and DX (X = F, Cl) elimination pathways of CDClCHFCl* were examined using a chemical activation technique; the molecules were generated with 92 kcal mol of vibrational energy in a room-temperature bath gas by a combination of CDCl and CHFCl radicals. The total unimolecular rate constant was 9.7 × 10 s, and branching fractions for each channel were 0.