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 kNu/ks ((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 13C NMR analysis of the products of the reactions of substrate enriched with 13C at the α-carbon, X-1-[α-13C]OTs (X = −OCH3 or −Me), with nucleophilic anions in 50:50 (v/v) TFE/water at 25 °C shows the formation of X-1-[β-13C]OH, X-1-[β-13C]OCH2CF3, and X-1-[β-13C]Nu (Nu = Br, Cl, CH3CO2, or Cl2CHCO2) from the trapping of symmetrical phenonium ion reaction intermediates X-2+. The observation of excess label in the α-position, [α-13C]/[β-13C] > 1.0, for both the water and nucleophile adducts, shows that these nucleophiles also react by direct substitution at X-1-[α-13C]OTs. The ratios of product yields, [α-13C]/[β-13C], and observed nucleophile selectivity (kNu/ks)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 kNu/ks for X-2+. Swain–Scott plots of log(kNu/ks) 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 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 | 0.001 |
| 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 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.007 | 0.001 |
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".