Unexpected medium effect on the mechanism for aminolysis of aryl phenyl carbonates in acetonitrile and H<sub>2</sub>O: transition-state structure in the catalytic pathway
Bibliographic record
Abstract
Upward curvature in the kinetic plots of pseudo first-order rate constants (k obsd ) vs. [amine] for the aminolysis of aryl phenyl carbonates (5a–5j) in MeCN demonstrates that these reactions proceed via a zwitterionic tetrahedral intermediate (T ± ) that partitions between catalyzed and uncatalyzed routes to give the products. Yukawa–Tsuno plots for the reactions of 5a–5j with piperidine result in excellent linear correlations with ρ Y = 4.82 and r = 0.47 for the uncatalyzed reaction versus ρ Y = 2.21 and r = 0.21 for the catalyzed reaction. Brønsted plots for reactions of 4-(ethoxycarbonyl)-phenyl phenyl carbonate (5f) with a series of cyclic secondary amines exhibit excellent linear correlations with β nuc = 0.87 and 0.58 for the uncatalyzed and catalyzed reactions, respectively. The ΔH ‡ and ΔS ‡ values are 0.92 kcal/mol and –50.1 cal/mol K, respectively, for the catalyzed reaction of 5f with piperidine. Deuterium kinetic isotope effects found for reactions of 5f with piperidine/deuterated piperidine are 0.84 (uncatalyzed) and 1.42 (catalyzed). Multi-parameter analysis supports a concerted catalytic pathway involving a six-membered cyclic transition state rather than a traditionally accepted stepwise pathway with an anionic intermediate. The current unexpected results, where T ± is the essential central intermediate in this aminolysis, contrast with previous calculation studies that deemed T ± unstable in gas phase or MeCN.
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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 | 0.001 |
| 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".