Solvent Effect on the α-Effect for the Reactions of Aryl Acetates with Butane-2,3-dione Monoximate and <i>p</i>-Chlorophenoxide in MeCN−H<sub>2</sub>O Mixtures
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Bibliographic record
Abstract
Second-order rate constants have been measured spectrophotometrically for the nucleophilic reactions of three substituted phenyl acetates with butane-2,3-dione monoximate (Ox(-)) as an alpha-nucleophile and p-chlorophenoxide (ClPhO(-)) as corresponding normal nucleophile, in MeCN-H2O mixtures of varying compositions at 25.0 +/- 0.1 degrees C. The reactivity of Ox(-) toward the aryl acetates decreases upon addition of MeCN to the reaction medium up to ca. 30 mol % MeCN, followed by a gradual increase in rate upon further addition of MeCN. A similar result has been obtained for the reaction of ClPhO(-) with the aryl acetates. However, the decrease in rate is more significant for the less reactive ClPhO(-) than for the more reactive Ox(-). Thus, for all the aryl acetates studied, Ox(-) exhibits a sizable alpha-effect (k(Ox)-/k(ClPhO)-) whose magnitude increases as the mol % MeCN in the reaction medium increases. The relative basicities (DeltapK(a)) of Ox(-) and ClPhO(-) have been determined spectrophotometrically using piperazine as a reference base. The DeltapK(a) values increase on increasing the mol % MeCN in the medium for both Ox(-) and ClPhO(-). The difference in the relative basicities of these nucleophiles (DeltaDeltapK(a)) becomes larger with increasing mol % MeCN. The plots of log k(Ox)-/k(ClPhO)- vs DeltaDeltapK(a) for the three substrates are linear with near-unit slope, indicating that the difference in the relative basicity of the nucleophiles is largely responsible for the increasing alpha-effect with medium composition in this system.
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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 | 0.001 | 0.001 |
| 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 it