Kinetics of ozonation. 4. Reactions of ozone with. cap alpha. -tocopherol and oleate and linoleate esters in carbon tetrachloride and in aqueous micellar solvents

Journal Article · Wed Oct 15 00:00:00 EDT 1986 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00281a033· OSTI ID:7246982

Giamalva, D H; Church, D F; Pryor, W A

Vitamin E (..cap alpha..-tocopherol; ..cap alpha..-T) is known to protect animals against the deleterious effects of ozone in polluted air; one such effect is the ozone-initiated autooxidation of polyunsaturated fatty acids (PUFA) that occur in membranes. In order to assess the possibility of a direct reaction of ozone with ..cap alpha..-T competing with the very fast ozone-PUFA reaction, we have measured the rates of reaction of ozone with ..cap alpha..-T, oleic acid, and linoleic acid. I CCl/sub 4/ as solvent, ..cap alpha..-T reacts with ozone with a rate constant of about 5500 M/sup -1/ s/sup -1/; methyl oleate and methyl linoleate react 2 orders of magnitude faster. In aqueous micellar solutions the rate constants for ..cap alpha..-T and the fatty acids are more similar. The k for the ozone/..cap alpha..-T reaction is about 1 x 10/sup 6/ M/sup -1/ s/sup -1/ at pH 7, but decreases as the solution becomes more acidic; the k's for oleic acid and linoleic acid are ca. 1 x 10/sup 6/ M/sup -1/ s/sup -1/ and exhibit no significant pH dependence. Since the ratio of fatty acids to ..cap alpha..-T in membranes is typically at least 100-1000 to 1, we conclude that the direct reaction of ozone with ..cap alpha..-T is unlikely. Thus, the protection that vitamin E provides to animals breathing ozone-containing air must result from vitamin E acting as a free radical scavenger. We have also detected the ..cap alpha..-tocopheroxyl radical as an intermediate from the reaction of ozone with ..cap alpha..-T both in CCl/sub 4/ and aqueous micelles using electron spin resonance spectroscopy. The authors suggest that the observation of this intermediate is consistent with an initial electron transfer from ..cap alpha..-T to ozone.

• Research Organization: Louisiana State Univ., Baton Rouge
• OSTI ID: 7246982
• Journal Information: J. Am. Chem. Soc.; (United States), Vol. 108:21
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
LINOLEIC ACID
CHEMICAL REACTIONS
OZONIZATION
OLEIC ACID
OZONE
VITAMIN E
AQUEOUS SOLUTIONS
CARBON TETRACHLORIDE
CHEMICAL REACTION KINETICS
ELECTRON SPIN RESONANCE
ELECTRON TRANSFER
EXPERIMENTAL DATA
MICELLAR SYSTEMS
PH VALUE
RADICALS
REACTION INTERMEDIATES
CARBOXYLIC ACIDS
CHLORINATED ALIPHATIC HYDROCARBONS
DATA
DISPERSIONS
HALOGENATED ALIPHATIC HYDROCARBONS
INFORMATION
KINETICS
MAGNETIC RESONANCE
MIXTURES
MONOCARBOXYLIC ACIDS
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
REACTION KINETICS
RESONANCE
SOLUTIONS
VITAMINS
550200* - Biochemistry
560300 - Chemicals Metabolism & Toxicology