Ab initio predictions and experimental confirmation of large tunneling contributions to rate constants and kinetic isotope effects for hydrogen atom transfer reactions

Journal Article · Wed Jun 11 04:00:00 EDT 1986 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00272a061· OSTI ID:5583834

Garrett, B C; Truhlar, D G; Bowman, J M; Wagner, A F; Robie, D; Arepalli, S; Presser, N; Gordon, R J

The interpretation of kinetic isotope effects (KIE's) involves potential energy barrier heights, vibrational effects of stretches and bends, and competition between overbarrier and tunneling mechanisms. In favorable cases, KIE's provide some of the most compelling evidence for or against detailed interpretations of the dynamics of reactive events. The present paper reports such a case in which the detailed question is the role of tunneling in hydrogen atom transfer reactions in the gas phase. In this communication the authors report new calculations and experiments on the bimolecular rate constant ratio k/sub 3//k/sub 4/ O + HD ..-->.. OH + D, O + HD ..-->.. OD + H, which, together with earlier results for k/sub 1/ and k/sub 2/ O + H/sub 2/ ..-->.. OH + H, O + D/sub 2/ ..-->.. OD + D provide strong evidence for the dominance of tunneling in all four reactions at temperatures below 500 K. For the present report previous results for reactions 1 and 2 and new results for 3 and 4 are fit to Arrhenius forms k/sub i/ = A/sub i/ exp(-E/sub i//RT) and k/sub i//k/sub j/ = A/sub ij/exp (E/sub ij//RT). Since the parameters depend on the temperature range used for the fit, this is indicated in every case.

• Research Organization: Chemical Dynamic Corp., Columbus, OH
• OSTI ID: 5583834
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 108:12; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400202* -- Isotope Effects
Isotope Exchange
& Isotope Separation
400800 -- Combustion
Pyrolysis
& High-Temperature Chemistry
500100 -- Environment
Atmospheric-- Basic Studies-- (-1989)
54 ENVIRONMENTAL SCIENCES
ACTIVATION ENERGY
ARRHENIUS EQUATION
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DATA
DEUTERIDES
DEUTERIUM
DEUTERIUM COMPOUNDS
ELEMENTS
ENERGY
EQUATIONS
EXPERIMENTAL DATA
FLUIDS
GASES
HYDROGEN
HYDROGEN COMPOUNDS
HYDROGEN DEUTERIDE
HYDROGEN ISOTOPES
HYDROGEN TRANSFER
INFORMATION
ISOTOPE EFFECTS
ISOTOPES
KINETICS
LIGHT NUCLEI
LOW TEMPERATURE
MEDIUM TEMPERATURE
NONMETALS
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
OXIDATION
REACTION KINETICS
STABLE ISOTOPES
TEMPERATURE DEPENDENCE
TUNNEL EFFECT