Comparison of Cu(II)-Promoted Leaving Group Stabilization of the Cleavage of a Homologous Set of Phosphate Mono-, Di-, and Triesters in Water, Methanol, and Ethanol
Bibliographic record
Abstract
The cleavage of a set of phosphate mono-, di-, and triesters having a Cu(II)-complexed 2-phenanthrolyl group at the ortho-position of a departing phenoxide was studied in water and ethanol. Experimentally observed pH/rate profiles, solvent deuterium kinetic isotope effects, and activation parameters are compared with those obtained in methanol. The pH/rate profile in each solvent exhibits an extended plateau due to solvent attack on forms designated as [Cu(II):1b/c](0) for the monoester, [Cu(II):2b](+), for the diester, and [Cu(II):3a](2+) for the triester. The solvent dkie values (k(H)/k(D)) for the three complexes are 0.91, 0.95, and 0.83 for decomposition of [Cu(II):1b/c](0) in water (W), methanol (M), and ethanol (E), 1.22, 1.09, and 1.29 for [Cu(II):2b](+) in W, M, and E, and 1.94, 2.2, and 1.96 for [Cu(II):3a](2+) in W, M, and E. Near unit, or slightly inverse values for the monoester are taken as evidence for little involvement of solvent in a highly dissociative TS for P-OAr cleavage, with slightly higher solvent dkie values for the diester signifying the onset of some solvent participation in assisting the nucleophilic displacement. The larger primary dkie for the triester gives evidence for a solvent-assisted delivery of ROH in the cleavage through a more associative mechanism. Activation parameters for each substrate in the solvents are compared, indicating that the transition from methanol to ethanol for each substrate involves a near cancellation of the ΔΔH(‡) and -TΔΔS(‡) values (25 °C) so that the respective rates in both solvents are very similar. The transition from alcohol to water produces variable effects, with ΔΔH(‡) and -TΔΔS(‡) values canceling for cleavage of the triester and being additive for the mono and diester, explaining their 100-500 rate reduction in passing from methanol to water. The rate enhancing effects of the Cu(II)-promoted leaving group assistance in all three solvents are substantial and estimated at 10(12)-10(15) for the monoester, 10(12)-10(14) for the diester, and 10(5) for the triester relative to their background reactions.
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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".