Catalytic Pathways and Kinetic Requirements for Alkanal Deoxygenation on Solid Tungstosilicic Acid Clusters
Bibliographic record
Abstract
Kinetic measurements and acid site titrations were carried out to interrogate the reaction network, probe the mechanism of several concomitant catalytic cycles, and explain their connection during deoxygenation of light alkanals (C n H 2 n O, n = 3–6) on tungstosilicic acid clusters (H 4 SiW 12 O 40 ) that leads to hydrocarbons (e.g., light alkenes, dienes, and larger aromatics) and larger oxygenates (e.g., alkenals). The three primary pathways are (1) intermolecular C═C bond formation, which couples two alkanal molecules in aldol-condensation reactions followed by rapid dehydration, forming a larger alkenal (C 2 n H 4 n –2 O), (2) intramolecular C═C bond formation, which converts an alkanal directly to an n -alkene (C n H 2 n ) by accepting a hydride ion from H donor and ejecting a H 2 O molecule, and (3) isomerization–dehydration, which involves self-isomerization of an alkanal to form an allylic alcohol and then rapid dehydration to produce an n -diene (C n H 2 n –2 ). The initial intermolecular C═C bond formation is followed by a series of sequential intermolecular C═C bond formation steps; during each of these steps an additional alkanal unit is added onto the carbon chain to evolve a larger alkenal (C 3 n H 6 n –4 O and C 4 n H 8 n –6 O), which upon its cyclization–dehydration reaction forms hydrocarbons (C tn H 2 tn –2 t, t = 2–4, including cycloalkadienes or aromatics). The intermolecular and intramolecular C═C bond formation cycles are catalytically coupled through intermolecular H-transfer events, whereas the intermolecular C═C bond formation and isomerization–dehydration pathways share a coadsorbed alkanal–alkenol pair as the common reaction intermediate. The carbon number of alkanals determines their hydride ion affinities, the stabilities of their enol tautomers, and the extent of van der Waals interactions with the tungstosilicic clusters; these factors influence the stabilities of the transition states or the abundances of reaction intermediates in the kinetically relevant steps and in turn the reactivities and selectivities of the various cycles.
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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 | 0.001 | 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".