Photochemical generation of thiophene analogs of 9‐fluorenyl cations
Bibliographic record
Abstract
Abstract The 9‐fluorenyl cation is a member of the 4N Hückel antiaromatic series of intermediates, first observed by time‐resolved spectroscopy on UV photo‐excitation of 9‐fluorenol. Thiophene analogs of 9‐fluorenol in which one of the annelated benzene rings is replaced by a thiophene were prepared in three regioisomeric forms, and subjected to preparative and laser flash photolysis. Photoproduct studies in methanol indicated products derived from the corresponding fluorenyl cations and radical intermediates. Time‐resolved spectroscopy showed transients which were assigned to the corresponding cations as evident from methanol quenching. The lifetimes and methanol quenching rates of these transients were compared with those of parent fluorenyl cation, and were found to be about two orders of magnitude more stable than the latter. On the other hand thermodynamic stabilities obtained from theoretical calculations based on isodesmic reactions of the open form cations, and NICS indicate that two of these ions (2 and 4) are less stable than 9‐fluorenyl cation, whereas the “side” isomer 3 is slightly more stable. Copyright © 2010 John Wiley & Sons, Ltd.
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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) | 0.002 | 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".