Échelles p<i>K</i><sub>HB</sub> et enthalpique du pouvoir accepteur de liaison hydrogène de thioéthers, thiols et disulfures
Bibliographic record
Abstract
The hydrogen bond acceptor (HBA) strength of 31 tetrahedral sulfur bases (thioethers, thiols, disulfides) has been measured by IR spectrometry from: (i) their 1:1 complexation constants with 4-fluorophenol in CCl4 at 25 °C (the pKHB scale); (ii) their HB enthalpies; and (iii) the frequency shifts, Δν(OH), of the ν(OH) band of 4-fluorophenol hydrogen bonded to sulfur. The comparison of the pKHB, ΔH°, and Δν(OH) scales points to their distinctive features. The HBA strength depends on: (i) the nature of the atomic site: oxygen bases are always stronger than sulfur bases, in agreement with the hard and soft acids and bases principle; (ii) the functionality of this atom (for sulfur bases: phosphine sulfur > thioamide > thioketone > thioether > thiol > isothiocyanate ~ disulfide); and (iii) the substituent effects on the function. The main substituent effects are: (i) the polarizability effect of alkyl groups; (ii) the field-inductive effect; (iii) the resonance effect; and (iv) the cyclization effect, which changes the percentage of the s character of sulfur lone pairs. In addition to the attachment to the sulfur atom, IR spectra show the attachment of 4-fluorophenol to the chlorine of MeSCH2Cl and MeSCH2CH2Cl, and the interaction to the π cloud of PhSMe, Ph2S, PhCH2SMe, and EtSCH=CH2. Key words: hydrogen bond, thioethers, thiols, disulfides, pKHB scale.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 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".