Dinuclear Zn(II) Complex Promotes Cleavage and Isomerization of 2-Hydroxypropyl Alkyl Phosphates by a Common Cyclic Phosphate Intermediate
Bibliographic record
Abstract
The kinetics and cleavage products of 2-hydroxypropyl p-nitrophenyl phosphate were determined in methanol containing the di-Zn(II) complex of bis-1,3-N1,N1'-(1,5,9-triazacyclododecyl)propane (4). Time-dependent 1H NMR spectra of the reaction mixture at sspH 9.8 +/- 0.1 show that the catalytic reaction proceeds via a cyclic phosphate (4-methylethylene phosphate, 2) that is subsequently cleaved into a kinetic mixture of two isomeric products, 2-hydroxypropyl methyl phosphate (3) and 1-hydroxypropan-2-yl methyl phosphate (3a), in a 29/71 ratio. In the presence of 4, the kinetic mixture of 3/3a is transformed into a thermodynamic mixture of 72/28 3/3a. The time-dependent 1H NMR spectra of 4 and a 22/78 mixture of 3/3a in CD3OH show that the formation of the thermodynamic mixture occurs on the same time scale as replacement of the P-OCH3 group of the 3/3a starting materials with OCD3. Detailed kinetic studies indicate that the dominant process for loss of the OCH3 group and equilibration of 3/3a is via a 4-catalyzed process where each of the isomers cyclizes to methylethylene phosphate (2), which subsequently reforms the 3/3a thermodynamic mixture. The kcatmax for 4-catalyzed cyclization of 3 and three other 2-hydroxypropyl O-alkyl phosphates (alkyl = CF3CH2- (6a), CH2FCH2- (6b), and CH3CH2- (6c)) has been determined, and the Brønsted plot comprising the log kcatmax vs leaving group sspKa that includes several previously studied 2-hydroxypropyl aryl phosphates is linear, following the expression log kcatmax = (-0.85 +/- 0.02) sspKa + (12.8 +/- 0.4). The betalg value of -0.85 suggests that the catalyzed cleavage of the P-OAr/OR bond has progressed to about 45% in the transition state. The combined results are analyzed in terms of two possible processes involving either a concerted reaction leading to the cyclic phosphate 2 from which the thermodynamic mixture of 3/3a is formed or a stepwise one involving a transient phosphorane whose predominant fate is to eliminate methoxide and proceed to 2 rather than partitioning between 3, 3a, and 2.
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".