The rates of HCl loss from energy-selected ethylchloride ions: A case of tunneling through an H-atom transfer barrier
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290 (US)
The dissociation rates of energy-selected ethylchloride and deuterated ethylchloride ions were measured as a function of the parent-ion internal energy by the method of photoelectron photoion coincidence. Previously performed {ital ab} {ital initio} calculations indicated that the rate-determining step for this reaction is an H-atom transfer from the {beta} carbon to the Cl atom via a substantial energy barrier of 92 kJ/mol (referenced to the zero-point energy). The ion internal energy range in which the experimental rates varied between 10{sup 5} and 10{sup 7} s{sup {minus}1} was found to lie well below the calculated barrier for H-atom transfer. The rates were modeled with the RRKM statistical theory which includes a tunneling step through an Eckart potential. The vibrational frequencies of both the normal and deuterated ethylchloride ions were determined by {ital ab} {ital initio} molecular-orbital methods. The theory accounted very well for the absolute rates including the strong deuterium isotope effect. The measured kinetic-energy release distribution appears nonstatistical. This indicates that the ion--dipole complex, which lies in between the transition state and the C{sub 2}H{sup +}{sub 4}+HCl products, is ineffective in randomizing the potential energy of the reverse activation barrier.
- OSTI ID:
- 6256386
- Journal Information:
- Journal of Chemical Physics; (USA), Vol. 94:5; ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CHLORINATED ALIPHATIC HYDROCARBONS
CHEMICAL REACTION KINETICS
DEUTERIUM
ISOTOPE EFFECTS
CHEMICAL REACTIONS
COINCIDENCE METHODS
DEUTERIUM COMPOUNDS
DISSOCIATION
HYDROCHLORIC ACID
PHOTOELECTRON SPECTROSCOPY
VIBRATIONAL STATES
COUNTING TECHNIQUES
ELECTRON SPECTROSCOPY
ENERGY LEVELS
EXCITED STATES
HALOGENATED ALIPHATIC HYDROCARBONS
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
INORGANIC ACIDS
ISOTOPES
KINETICS
LIGHT NUCLEI
NUCLEI
ODD-ODD NUCLEI
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
REACTION KINETICS
SPECTROSCOPY
STABLE ISOTOPES
400201* - Chemical & Physicochemical Properties