Acid enol and dihydropyridine intermediates in pyridylketene hydration A computational study
Bibliographic record
Abstract
3-Pyridylketene (3-1) is found experimentally to undergo hydration forming an intermediate acid enol 3-2; whereas 2- and 4-pyridylketenes (2-1 and 4-1), instead, form (carboxymethylene)dihydropyridine intermediates 2-4 and 4-4, which live much longer than 3-2. Density functional calculations have been carried out to elucidate the hydration reactivity of these ketenes, and reveal that the dihydropyridine intermediates 2-4 and 4-4 are more stable than the unobserved acid enols 2-2 and 4-2 by 6.23 and 12.2 kcal/mol, respectively. For 3-1 a pathway was calculated utilizing two H2O molecules leading to the acid enol intermediate 3-2, which then forms 3-pyridylacetic acid (3-3). Hydration of 4-pyridylketene involves net 1,6-addition of water, and a pathway involving a bridge of six H2O molecules connecting the pyridyl nitrogen and the carbonyl carbon was determined. Key words: mechanisms of pyridylketene hydration, computations, enols, dihydropyridines.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".