Pyridine <i>N</i> ‐oxide and pyridine‐ <i>d</i> <sub>5</sub> <i>N</i> ‐oxide: an electrospray/tandem mass spectrometric study carried out at high mass resolution
Bibliographic record
Abstract
A mass spectrometric study of pyridine N-oxide and pyridine-d5 N-oxide was carried out with a hybrid quadrupole/time-of-flight (TOF) mass spectrometer coupled with an electrospray (ES) source. In addition to the observation of protonated, sodiated, and proton-bound dimers of pyridine N-oxide and pyridine-d5 N-oxide, mass scans revealed the presence of several doubly-charged ion species. Doubly-charged ions of m/z 191 were identified as diprotonated tetramers of pyridine N-oxide; a structure has been proposed for the diprotonated tetramer and its energy relative to that of protonated pyridine N-oxide has been obtained from geometry optimizations. The principal ion species observed were subjected to collision-induced dissociation; accurate mass measurements were made of each fragment ion so as to determine its elemental composition. On the basis of mass spectrometric evidence, it is suggested that dissociation of pyridine N-oxide may occur during the ES process and the resulting fragments become embedded in doubly-charged ions. The proton affinity for both pyridine N-oxide and pyridine-d5 N-oxide was calculated; the difference between these proton affinities was compared with an experimentally determined difference between the proton affinities of pyridine N-oxide and pyridine-d5 N-oxide.
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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) | 0.001 | 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".