Evidence for [1,5] sigmatropic rearrangements of CLA in heated oils
Bibliographic record
Abstract
Linoleic acid was heated at 200 degrees C under helium. Analysis of degradation products by GC on a long polar open tubular capillary column showed the presence of CLA isomers. The identified mono trans CLA isomers were cis-9,trans-11, trans-9,cis-11, trans-10,cis-12, cis-10,trans-1 2, trans-8,cis-10, and cis-11,trans-13 18:2 acids. Oils containing different levels of linoleic acid (peanut, sesame seed, and safflower seed oils) were also heat treated, resulting in similar CLA distributions. Elution order was confirmed using cis-9,trans-11 and trans-10,cis-1 2 acid methyl esters standards and their respective configuration isomers (trans-9,cis-11, cis-10,trans-12), obtained after mild selenium-catalyzed isomerization. These results indicated that two conjugated mono trans isomers of 18:2 acid, cis-8,trans-10 and trans-11,cis-13 18:2 were absent from the series, thus strongly suggesting that some constraints were preventing their formation. By heating pure methyl rumenate (cis-9,trans-11 18:2) under similar conditions, isomerization resulted principally in a nearly equimolar mixture of methyl rumenate and trans-8,cis-10 18:2. Similarly, the methyl ester of trans-10,cis-12 18:2 acid was partially transformed into cis-11 ,trans-13 18:2 acid. Respective geometrical isomers were also formed in trace amounts. A concerted pericyclic isomerization mechanism, a [1,5] sigmatropic rearrangement, is proposed that limits the conjugated system to isomerization from a cis-trans acid to a trans-cis acid, and vice versa. This mechanism is consistent with undetected cis-8,trans-10 and trans-11,cis-13 18:2 isomers in heated oils containing linoleic acid.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".