Medium effect on the α-effect for nucleophilic substitution reactions of <i>p</i>-nitrophenyl acetate with benzohydroxamates and <i>m</i>-chlorophenoxide in DMSO–H<sub>2</sub>O mixtures as contrasts with MeCN–H<sub>2</sub>O mixtures: comparing two very different polar aprotic solvent components
Bibliographic record
Abstract
A kinetic study is reported on nucleophilic substitution reactions of p-nitrophenyl acetate (1a) with three α-effect nucleophiles, benzohydroxamate (BHA – ), p-methylbenzohydroxamate (MBHA – ), and p-methyl-N-methylbenzohydroxamate (M 2 BHA – ), and a reference nucleophile, m-chlorophenoxide (m-ClPhO – ), in DMSO–H 2 O mixtures of varying compositions at 25.0 ± 0.1 °C. Second-order rate constants for the reactions with BHA – and MBHA – decrease upon addition of DMSO to the reaction medium up to 60 mol % DMSO and then increase thereafter only a little. In contrast, M 2 BHA – and m-ClPhO – become much more reactive as the DMSO content in the medium increases. Such contrasting medium effects on reactivity are consistent with the report that hydroxamic acids behave as OH acids in H 2 O but as NH acids in dipolar aprotic solvents (e.g., DMSO and MeCN). It has been concluded that BHA – and MBHA – form an equilibrium of a reactive form I with less reactive species II in DMSO–H 2 O mixtures and the position of the equilibrium is dependent on solvent compositions. BHA – and MBHA – exhibit the α-effect in H 2 O but not in in 90 mol % DMSO. In contrast, the α-effect yielded by M 2 BHA – increases steeply up to 70 mol % DMSO and then levels off thereafter.
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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) | 0.001 | 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 | 0.001 |
| 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".