Reductive demercuration of hex-5-enyl-1-mercuric bromide by metal hydrides. Rearrangement, isotope effects, and mechanism
The use of the rearrangement of hex-5-enyl radical intermediates as a mechanistic probe has been examined in the reductive demercurations of hex-5-enyl-l-mercuric bromide (1). Methylcyclopentane and 1-hexene are the major products from reductions of 1 by sodium borohydride, lithium aluminum hydride, and tri-n-butyltin hydride. The formation of methylcyclopentane and the absence of cyclohexane are consistent with a noncage, free-radical chain mechanism for these reductions. The sodium amalgam reduction of 1 produces only 1-hexene. Hex-5-en-l-ol and a peroxide are formed from sodium borohydride reductions of 1 in the presence of molecular oxygen. Isotope effects for transfer of hydrogen to the intermediate hex-5-enyl radicals have been determined from the 1-hexene/methylcyclopentane product ratio, since rearrangement of the 5-hexenyl radical competes with hydrogen abstraction. The magnitude of these isotope effects (1.8 +- 0.2) is the same for reductive demercurations of 1 by sodium borohydride, lithium aluminum hydride, and tri-n-butyltin hydride; these results provide evidence for a common hydrogen-transfer agent, such as hex-5-enyl-1-mercuric hydride, for all of these metal-hydride reductions. The validity of the competing rearrangement method of determining hydrogen isotope effects has been demonstrated by determining the isotope effect for the tri-n-butyltin hydride reduction of 6-bromo-1-hexene (2.8 +- 0.2) at 40/sup 0/C.
- Research Organization:
- Univ. of Arkansas, Fayetteville
- OSTI ID:
- 7334367
- Journal Information:
- J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 98:19; ISSN JACSA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400302* -- Organic Chemistry-- Isotope Effects-- (-1987)
ALKANES
ALKENES
ALLOYS
CHEMICAL REACTION KINETICS
CHEMICAL REACTION YIELD
CHEMICAL REACTIONS
CYCLOALKANES
DEUTERIUM
HEXENES
HYDRIDES
HYDROCARBONS
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
ISOTOPE EFFECTS
ISOTOPES
KINETICS
LIGHT NUCLEI
MERCURY ALLOYS
NUCLEI
ODD-ODD NUCLEI
ORGANIC BROMINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC MERCURY COMPOUNDS
REACTION KINETICS
REDUCTION
STABLE ISOTOPES
YIELDS