Melting Behavior of Crown Thioethers: Correlation of Entropy Changes with Conformational Disorder
Bibliographic record
Abstract
We have examined the following crown thioethers by differential scanning calorimetry from −90 °C, or lower, up to their melting points: 1,4,7-trithiacyclononane (9S3); 1,5,9-trithiacyclododecane (12S3); 1,4,7,10-tetrathiacyclododecane (12S4); 1,4,8,11-tetrathiacyclotetradecane (14S4); 1,4,7,10,13-pentathiacyclopentadecane (15S5); and 1,5,9,13-tetrathiacyclohexadecane (16S4). We have identified new solid−solid phase transitions above room temperature in 12S3, in the α-phase of 14S4, in 15S5, and in both the α-phase and β-phase of 16S4. Of those crown thioethers examined, only 9S3 and 12S4 do not show any solid−solid phase transitions. From an analysis of the entropy of fusion, we find that only the high-temperature solid phase of 16S4 is orientationally disordered. Analysis of the entropy changes associated with the solid−solid phase transitions and with fusion indicate that all except 12S4 have considerably more conformational freedom in the melt than in the room-temperature solid. Insight into these conformational changes is of considerable importance for understanding complexation of thioethers to metals.
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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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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 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".