Reduction of benzophenone with metal hydrides. Kinetic isotope effect and substituent effect study
Carbonyl carbon kinetic isotope effects (KIEs) have been determined for the reduction of benzophenone-7-/sup 14/C with various metal hydrides at 25/degrees/C. The observed KIEs are as follows: BH/sub 3//THF, /sup 12/k//sup 14/k = 1.035 /plus minus/ 0.002; AlH/sub 3//Et/sub 2/O, 1.021 /plus minus/ 0.004; 9-BBN/THF, 1.027 /plus minus/ 0.004; DIBAL/hexane, 1.000 /plus minus/ 0.003; LiAlH/sub 4//THF, 1.017 /plus minus/ 0.007. The relative reactivities of ortho-, meta-, and para-substituted benzophenones with these reagents were also determined by the composition experiments. The absence of /sup 14/C KIE, the small sigma value (0.5), and the absence of steric rate retardation due to ortho substituents in the reduction of the ketone with DIBAL suggest that the reaction goes through the rate-determining electron transfer from DIBAL to the ketone. The reactions of other reducing agents showed positive KIE as well as a variable extent of steric effect and are concluded to proceed via a polar mechanism. The difference in the nature of the transition state is discussed on the basis of these results. 32 references, 6 figures, 2 tables.
- Research Organization:
- Osaka Univ. (Japan)
- OSTI ID:
- 6254471
- Journal Information:
- J. Org. Chem.; (United States), Vol. 53:4
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALUMINIUM HYDRIDES
ISOTOPIC EXCHANGE
BENZOPHENONE
BORON HYDRIDES
LITHIUM HYDRIDES
TETRAHYDROFURAN
CARBON 12
CARBON 14
EXPERIMENTAL DATA
ISOTOPE EFFECTS
ALKALI METAL COMPOUNDS
ALUMINIUM COMPOUNDS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BORON COMPOUNDS
CARBON ISOTOPES
DATA
EVEN-EVEN NUCLEI
FURANS
HETEROCYCLIC COMPOUNDS
HYDRIDES
HYDROGEN COMPOUNDS
INFORMATION
ISOTOPES
KETONES
LIGHT NUCLEI
LITHIUM COMPOUNDS
NUCLEI
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
RADIOISOTOPES
STABLE ISOTOPES
YEARS LIVING RADIOISOTOPES
400201* - Chemical & Physicochemical Properties
400202 - Isotope Effects
Isotope Exchange
& Isotope Separation