Primary deuterium isotope effects in the oxidation of Benzyl-a-d alcohol by transition elements and related reagents: mechanisms of electron transfer
In order to assess the structural features of the activated complex in hydrogen transfer processes, benzyl-..cap alpha..-d alcohol has been oxidized to the aldehyde over a broad range of accurately controlled temperatures with four reagents: mangansese dioxide, nickel dioxide, cerium(IV), and 2, 3-dichloro-5, 6-dicyanobenzoquinone (DDQ). Estimation of the benzaldehyde (C/sub 6/H/sub 5/CHO/C/sub 6/H/sub 5/CDO) product ratios was carried out by means of a mass spectrometric technique developed for the high precision measurements required in applying the data as a mechanistic criterion. The principal results are the striking temperature-dependent k/sub H/k/sub D/ values measured for the MnO/sub 2/ and NiO/sub 2/ systems and the equally striking temperature-independent isotope effects measured for the Ce(IV) and DDQ systems. For MnO/sub 2/ and NiO/sub 2/, the activation parameters are of magnitudes which indicate tunneling in a reaction of linear hydrogen transfer. Conclusions drawn from comparison of Cr(VI), Mn(IV) and Ni(IV) oxidations of normal alcohols is that the coupled electron and hydrogen-transfer events in oxidation by transition elements tend to occur within the planar structure of a 5-membered cyclic arrangement of reaction centers. The temperature-independent results of the Ce(IV) and DDQ oxidations are interpreted in terms of an activated complex of cyclic structure, but with a nonlinear H-transfer geometry.
- Research Organization:
- Univ. of Delaware, Newark
- OSTI ID:
- 6389692
- Journal Information:
- J. Org. Chem.; (United States), Vol. 44:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALCOHOLS
CHEMICAL REACTIONS
BENZALDEHYDE
CHEMICAL REACTION YIELD
BENZOQUINONES
CERIUM
DEUTERIUM
ISOTOPE EFFECTS
DEUTERIUM COMPOUNDS
MANGANESE OXIDES
NICKEL OXIDES
ACTIVATION ENERGY
CHEMICAL REACTION KINETICS
COMPARATIVE EVALUATIONS
IONS
MASS SPECTRA
MEDIUM TEMPERATURE
OXIDATION
TEMPERATURE DEPENDENCE
ALDEHYDES
AROMATICS
CHALCOGENIDES
CHARGED PARTICLES
ELEMENTS
ENERGY
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
HYDROXY COMPOUNDS
ISOTOPES
KINETICS
LIGHT NUCLEI
MANGANESE COMPOUNDS
METALS
NICKEL COMPOUNDS
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
QUINONES
RARE EARTHS
REACTION KINETICS
SPECTRA
STABLE ISOTOPES
TRANSITION ELEMENT COMPOUNDS
YIELDS
400302* - Organic Chemistry- Isotope Effects- (-1987)
400301 - Organic Chemistry- Chemical & Physicochemical Properties- (-1987)