Mechanism of the thermal (1,5)-H shift in cis-1,3-pentadiene. Kinetic isotope effect and vibrationally assisted tunneling

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

DOI:https://doi.org/10.1021/ja00272a017· OSTI ID:5532554

Dormans, G J.M.; Buck, H M

Ab initio 3-21 G calculations have been performed for the (1,5)-H shift in cis-1,3-pentadiene. A transition state of C/sub s/ symmetry has been compared with one of C/sub 2nu/ symmetry. The lowest energy configuration of this latter structure has B/sub 1/ symmetry and must therefore be described by an open-shell calculation. The energy of this structure is favored by 5.2 kcal/mol over the one of C/sub s/ symmetry. Both structures are found to be real transition states. Both the calculated reaction rates and the kinetic isotope effects are found to be considerably smaller than the observed ones. A mechanism is suggested in which tunneling takes place between high-vibrational states of the reactant and the product. It is shown that this mechanism is most likely for the transition state of C/sub 2nu/ symmetry. The calculated tunneling rates indicate that the (1,5)-H shift in cis-1,3-pentadiene mainly takes place via this mechanism.

• Research Organization: Eindhoven Univ. of Technology, Netherlands
• OSTI ID: 5532554
• Journal Information: J. Am. Chem. Soc.; (United States), Vol. 108:12
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ELECTRONIC STRUCTURE
ISOTOPE EFFECTS
TUNNEL EFFECT
PENTADIENES
CALCULATION METHODS
CHEMICAL REACTION KINETICS
TEMPERATURE DEPENDENCE
THEORETICAL DATA
VIBRATIONAL STATES
DATA
DIENES
ENERGY LEVELS
EXCITED STATES
HYDROCARBONS
INFORMATION
KINETICS
NUMERICAL DATA
ORGANIC COMPOUNDS
POLYENES
REACTION KINETICS
400302* - Organic Chemistry- Isotope Effects- (-1987)