Observation of excited state proton transfer reactions in 2-phenylphenol and 2-phenyl-1-naphthol and formation of quinone methide species
Bibliographic record
Abstract
The excited state intramolecular proton transfer (ESIPT) reactions from a phenol (naphthol) to a carbon atom in the adjacent aromatic ring of 2-phenylphenol (1) and 2-phenyl-1-naphthol (4) are prototypical examples of intramolecular proton transfer not mediated by solvent molecules. Femtosecond time-resolved transient absorption (fs-TA) studies are conducted for the first time to directly probe the formation of quinone methide (QM) species generated from the ESIPT pathways of 1 and 4. Steady-state absorption experiments demonstrated 1 exists mainly in its non-deprotonated form in neat MeCN and in water-MeCN solutions. Observation of the phenolate form in water-containing solution (MeCN-H2O, 1 : 1, v : v) in fluorescence spectra demonstrates the occurrence of an ESPT reaction between 1 and the surrounding water molecules. In neat MeCN a transient species that absorbs around 520 nm was detected in fs-TA spectra and was assigned to the QM species formed by ESIPT to the 2'-position. This transient signal is strengthened in cyclohexane. In a water-MeCN solution, an additional transient species assigned to the QM species at the 4'-position of 1 was also detected that absorbs around 485 nm. Similar results for 4 were observed, with the absorbance of the transient species being more intense, which suggests there is more efficient production of the QM species from 4, consistent with quantum yields for deuterium exchange in the distal ring reported for these compounds.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 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) | 0.000 | 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 teacher head, 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".