α-Monodeuterated Benzyl Alcohols and Phosphobetaines from Reactions of Aromatic Aldehydes with a Water/D<sub>2</sub>O-Soluble Phosphine
Bibliographic record
Abstract
With the aim of learning more about the bleaching action of pulps by (hydroxymethyl)phosphines, we reacted several benzaldehydes, containing MeO, Me, OH, or halogen substituents, with tris(3-hydroxypropyl)phosphine, [HO(CH2)3]3P, in aqueous solution at 90 degrees C under argon. Effective reduction of the aldehydes to the corresponding benzyl alcohols with concomitant oxidation of the phosphine to the phosphine oxide takes place, the reaction proceeding via an initially formed phosphonium species. When the reactions are carried out in D2O, the benzyl alcohol product from 3,4-dimethoxybenzaldehyde contains one deuterium atom at the benzyl-carbon atom, consistent with the last step of the mechanism involving a carbanion intermediate. With syringaldehyde (3,5-dimethoxy-4-hydroxy-benzaldehyde), the reduction product (syringyl alcohol) is more reactive toward the phosphine than is the starting aldehyde, and a zwitterionic, phosphobetaine product is formed. In D2O, the zwitterion benzyl protons and protons of the hydroxypropyl-CH2 adjacent to the P atom undergo H/D exchange via presumed phosphorus ylide intermediates. Under the same aqueous reaction conditions, tris(3-hydroxypropyl)phosphine, [HO(CH2)3]3P (THPP), does not undergo redox reactions with aliphatic aldehydes but simply promotes a base-catalyzed self-condensation (aldol) reaction. THPP reduction of an aromatic ketone is sluggish, presumably because the carbonyl C-atom is less electrophilic than that present in an aromatic aldehyde.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 teacher head, 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".