ESR investigation of ester. pi. -cation radicals in a freon matrix at low temperatures: evidence for unusual barriers to methyl group rotation and intramolecular bonding
Journal Article
·
· J. Phys. Chem.; (United States)
..gamma..-Irradiation of dilute solutions of a number of esters in CFCl/sub 3/ at 77 K is shown by ESR spectroscopy to produce the ..pi..-cation radicals of these molecules. The ..pi..-cations formed are those of the methyl and ethyl formates, acetates, and propionates. Larger esters containing propyl and butyl side chains are suggested to be unstable toward deprotonation at 77 K. Synthesis of deuterium-labeled compounds was employed to assign proton hyperfine couplings to specific sites in the ..pi..-cation radicals. The ..pi..-cations of the ethyl esters show unusually large couplings to the terminal methyl groups. In addition, large barriers to methyl group rotation are found for both the methyl and ethyl ester cation radicals. The large barriers suggest intermolecular bonding between the alkyl group and the carbonyl oxygen in the ester functional group. Such a hypothesis is supported by the finding of a torsional motion in the terminal methyl group of ethyl formate ..pi..-cation which has a ca. 1.7 kcal/mol activation energy barrier. It is suggested that a new intramolecular ..pi..*-bond is responsible for the formation of cyclic rings in the methyl- and ethyl-substituted ester cation radicals.
- Research Organization:
- Oakland Univ., Rochester, MI
- OSTI ID:
- 6562543
- Journal Information:
- J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 88:9; ISSN JPCHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400600* -- Radiation Chemistry
CHEMICAL BONDS
CHEMICAL RADIATION EFFECTS
CHEMISTRY
DATA
DEUTERIUM
ELECTROMAGNETIC RADIATION
ELECTRON SPIN RESONANCE
ESTERS
EXPERIMENTAL DATA
FREONS
GAMMA RADIATION
HALOGENATED ALIPHATIC HYDROCARBONS
HYDROGEN ISOTOPES
INFORMATION
IONIZING RADIATIONS
ISOTOPES
LABELLED COMPOUNDS
LIGHT NUCLEI
MAGNETIC RESONANCE
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
RADIATION CHEMISTRY
RADIATION EFFECTS
RADIATIONS
RADICALS
RESONANCE
SPECTRA
STABLE ISOTOPES
400600* -- Radiation Chemistry
CHEMICAL BONDS
CHEMICAL RADIATION EFFECTS
CHEMISTRY
DATA
DEUTERIUM
ELECTROMAGNETIC RADIATION
ELECTRON SPIN RESONANCE
ESTERS
EXPERIMENTAL DATA
FREONS
GAMMA RADIATION
HALOGENATED ALIPHATIC HYDROCARBONS
HYDROGEN ISOTOPES
INFORMATION
IONIZING RADIATIONS
ISOTOPES
LABELLED COMPOUNDS
LIGHT NUCLEI
MAGNETIC RESONANCE
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
RADIATION CHEMISTRY
RADIATION EFFECTS
RADIATIONS
RADICALS
RESONANCE
SPECTRA
STABLE ISOTOPES