The Site of Protonation Affects the Dissociation of Protonated a- and b-Pinene Ions
Bibliographic record
Abstract
The unimolecular reactions of protonated α- and β-pinene ions were explored with a combination of collision-induced dissociation tandem mass spectrometry and theory. The two main dissociation reactions in each ion lead to the losses of neutral propene and isobutene. The difference observed between the two ions is a greater relative abundance of propene loss in the case of protonated a-pinene. Both ions were found to dissociate over the same minimum energy reaction pathway, the only difference being the site of initial protonation in the two ions. a-Pinene preferentially protonates at the bridging carbon, while b-pinene can only significantly protonate at the exocyclic double bond. This leads to a lower appearance energy for loss of isobutene, and thus relatively greater m/z 81 fragment ion abundance for b-pinene.
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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 | 0.001 |
| 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 | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".