Catalysis of the methanolysis of acetylimidazole by lanthanum triflate
Bibliographic record
Abstract
Methanolysis of acetylimidazole (1) and N-acetylimidazolepentamine-Co(III) (2) was found to be markedly accelerated in the presence of La(OTf) 3 . Potentiometric titration of a solution of La 3+ (OTf - ) 3 gave a pK a for the metal bound CH 3 OH of 7.22. The kinetics of methanolysis of 1 and 2 were measured at 25°C at various pH under buffered conditions as a function of increasing La 3+ . Analysis of both the kinetic and potentiometric data indicates that the catalytically active species is a La 3+ -dimer, bridged by two methoxides, (CH 3 OH) n La 3+ (CH 3 O - ) 2 La 3+ (CH 3 OH) n . The maximum second-order rate constants for attack of the dimer on 1 and 2 are 1.50 × 10 3 M -1 s -1 and 1.42 × 10 2 M -1 s -1 respectively and both processes adhere to titration of a La 3+ (CH 3 OH) to generate the active form. The results are explained in terms of a mechanism where the methoxy-bridged La 3+ dimer transiently breaks a La 3+ -OCH 3 bond to expose both a CH 3 O - nucleophile and a La 3+ which can act as a Lewis acid. Unlike the situation in water, the methanol results indicate that the medium greatly stabilizes and solubilizes the active dimer without the necessity of creating specially designed ligands to stabilize the dinuclear core.Key words: lanthanum ion, catalysis, methanolysis, activated amide.
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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".