| DOI | Resolve DOI: https://doi.org/10.1021/jo00122a026 |
|---|
| Author | Search for: Bowry, V.W.1 ; Search for: Ingold, K. U.1 |
|---|
| Name affiliation | - National Research Council Canada. NRC Steacie Institute for Molecular Sciences
|
|---|
| Format | Text |
|---|
| Type | Article |
|---|
| Journal title | The Journal of Organic Chemistry |
|---|
| ISSN | 0022-3263 |
|---|
| Volume | 60 |
|---|
| Issue | 17 |
|---|
| Pages | 5456–5467; # of pages: 12 |
|---|
| Subject | alpha tocopherol; radical; autooxidation; lipid peroxidation; reaction analysis |
|---|
| Abstract | Rate constants which have been reported for the bimolecular self-reaction of α-tocopheroxyl radicals vary by about 5 orders of magnitude. We have found that the observed bimolecular rate constant can vary by about a factor of 7 during a single, but typical experiment, e.g., in chlorobenzene at 37 °C from ca. 7 x 103 M-1 s-1 initially to ca. 1 x 103 M-1 s-1 finally. The overall reaction involves a disproportionation with the transfer of a hydrogen atom from the 5-methyl group of one radical to the phenoxyl oxygen atom of the other radical forming α-tocopherol and an o-quinone methide. In the slow regime (which corresponds to the true reaction of two α-tocopheroxyl radicals) this disproportionation has a deuterium kinetic isotope effect of 3.7. The bizarre kinetic behavior observed with α-tocopheroxyl radicals has been traced to a very minor impurity which will be present in any normal sample of α-tocopherol. The impurity in question is a bisphenol in which two α-tocopherol moieties have become linked through their 5-methyl carbon atoms. This bisphenol is a "natural" impurity in α-tocopherol since it will be formed upon exposure of α-tocopherol to air. The coupling of two o-quinone methide molecules yields a spiro-dimer which is then reduced to the bisphenol, probably by unoxidized α-tocopherol. © 1995 American Chemical Society. |
|---|
| Publication date | 1995 |
|---|
| Language | English |
|---|
| Peer reviewed | Yes |
|---|
| NPARC number | 21276588 |
|---|
| Export citation | Export as RIS |
|---|
| Report a correction | Report a correction |
|---|
Record identifier | f3fd8f98-d046-410e-b73a-fdbb456970d9 | | Record created | 2015-10-13 |
|---|
| Record modified | 2019-08-20 |
|---|
