I. Kinetic and mechanistic study of the (4+4) dimerization of 2,3-dimethylene-2,3-dihydrofuran. II. Preparation of 2,3-dimethylene-2,3-dihydrobenzo(B)furan by the flash vacuum pyrolysis of 2-methyl-3-benzo(B)furylmethyl benzoate. III. Reaction of 2,3-dimethylene-2,3-dihydrofuran with triplet oxygen
A kinetic and mechanistic study of the (4+4) dimerization of 2,3-dimethylene-2,3-dihydrofuran (1) has been carried out based on the secondary deuterium kinetic isotope effects (2/sup 0/D KIE), substituent effects and solvent effects. The 2/sup 0/D KIE was studied by measuring the rate constants, k/sub 1/, k/sub 2/, k/sub 3/, and K/sub 4/, respectively, for the (4+4) dimerization of 1,2-methylene-3-dideuteriomethylene-2,3-dihydrofuran (2), 2-dideuteriomethylene-3-methylene-2,3-dihydrofuran (3) and 2,3-bis(dideuteriomethylene)-2,3-dihydrofuran (4). The relation among k/sub 1/-k/sub 4/ at -30.0/sup 0/C was found to be k/sub 2//k/sub 1/ = k/sub 4//k/sub 1/ = 1.86 and k/sup 1/ = k/sub 3/. This result and the insignificant solvent effects that have been observed lead to the conclusion that the (4+4) dimerization of 1 proceeds via stepwise mechanism involving a diradical intermediate. 2,3-Dimethylene-2,3-dihydrobenzo(b)furan (5) was synthesized by the flash vacuum pyrolysis of 2-methyl-3-benzo(b)furylmethyl benzoate. The chemical reactions of 5, which were investigated in this study, include thermal dimerization reactions and Diels-Alder reactions. The dimerization reaction of 5 gave both (4+2) and (4+) dimers. The formation of cyclic peroxides from the reactions of 1 and its 5-methyl and 5-tert-butyl derivatives with triplet oxygen was investigated. Thermolysis of a cyclic peroxide gave dialdehyde, hydroxyl aldehyde and diol as the products.
- Research Organization:
- Iowa State Univ. of Science and Technology, Ames (USA)
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 6036372
- Country of Publication:
- United States
- Language:
- English
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(4 + 4) dimerization of 2,3-dimethylene-2,3-dihydrofuran: secondary deuterium kinetic isotope effect evidence of a two-step mechanism
Related Subjects
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
400302 -- Organic Chemistry-- Isotope Effects-- (-1987)
ALKENES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DEUTERIUM
DIMERIZATION
FURANS
HETEROCYCLIC COMPOUNDS
HYDROCARBONS
HYDROGEN ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPE EFFECTS
ISOTOPES
KINETICS
LIGHT NUCLEI
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
POLYMERIZATION
REACTION KINETICS
STABLE ISOTOPES
TRACER TECHNIQUES