Evidence for [1,5] sigmatropic rearrangements of CLA in heated oils
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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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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 it