Swain–Scott relationships for nucleophile addition to ring-substituted phenonium ions
Bibliographic record
Abstract
The products of the reactions of 2-(4-methoxyphenyl)ethyl tosylate (MeO-1-OTs) and 2-(4-methyphenyl)ethyl tosylate (Me-1-OTs) with nucleophilic anions were determined for reactions in 50:50 (v/v) trifluoroethanol (TFE) / water at 25 °C. In many cases, the nucleophile selectivity k Nu /k s ((mol/L) −1 ) for reactions of nucleophile and solvent, calculated from the ratio of product yields, depends upon [Nu − ]. This demonstrates the existence of competing reaction pathways, which show different selectivities for reactions with nucleophiles. A 13 C NMR analysis of the products of the reactions of substrate enriched with 13 C at the α-carbon, X-1-[α- 13 C]OTs (X = −OCH 3 or −Me), with nucleophilic anions in 50:50 (v/v) TFE/water at 25 °C shows the formation of X-1-[β- 13 C]OH, X-1-[β- 13 C]OCH 2 CF 3 , and X-1-[β- 13 C]Nu (Nu = Br, Cl, CH 3 CO 2 , or Cl 2 CHCO 2 ) from the trapping of symmetrical phenonium ion reaction intermediates X-2 + . The observation of excess label in the α-position, [α- 13 C]/[β- 13 C] > 1.0, for both the water and nucleophile adducts, shows that these nucleophiles also react by direct substitution at X-1-[α- 13 C]OTs. The ratios of product yields, [α- 13 C]/[β- 13 C], and observed nucleophile selectivity (k Nu /k s ) obs were used to dissect the contribution of nucleophile addition at Me-1-OTs and trapping of X-2 + to the product yields. The product yields from partitioning of the intermediate gave the nucleophile selectivity k Nu /k s for X-2 + . Swain–Scott plots of log(k Nu /k s ) are correlated by slopes of s = 0.78 and s = 0.73 for reactions of MeO-2 + and Me-2 + , respectively. This shows that the sensitivity of bimolecular substitution at X-2 + to changes in nucleophile reactivity is smaller than for nucleophilic substitution at the methyl iodide.
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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 | 0.002 |
| 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) | 0.001 | 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 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".