Structural, Vibrational, and Electronic Characteristics of Enyne Macrocycles as a Function of Ring Strain
Bibliographic record
Abstract
The cross-conjugated macrocycles 8a − e and acyclic model compound 12 have been synthesized and thoroughly analyzed by 1 H and 13 C NMR, UV, IR, and Raman spectroscopies, and by X-ray crystallography. The increasing ring strain and resultant changes in the double and triple bond orders are clearly detailed in the Raman and 13 C NMR spectra, as well as in the X-ray structures. Correlations between 13 C NMR shifts, bond angles, and Raman frequencies are essentially linear for the butadiynyl and olefinic moieties. The most highly strained system, 8a, displays interior alkylidene bond angles that are reduced to 108° and alkyne angles reduced to as little as 155°. The electronic absorption spectrum of 8a shows evidence of through-space homoconjugation that is manifested as a bathochromic shift of the absorption band arising from the in-plane π-system. The absorption bands from the out-of-plane π-electron systems of the more strained cycles 8a and 8b show slight bathochromic shifts as compared with the less strained systems 8c − e and acyclic 12 . Ring strain, however, has a surprisingly small effect on the electronic absorption energies of these macrocycles.
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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 | 0.000 |
| 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".