Photohydration and Photosolvolysis of Biphenyl Alkenes and\nAlcohols via Biphenyl Quinone Methide-type Intermediates\nand Diarylmethyl Carbocations
Bibliographic record
Abstract
Evidence is presented for the photochemical generation of novel biphenyl quinone methide (BQM)-type intermediates on photolysis of hydroxybiphenyl alkenes <b>7</b> and <b>8</b> and hydroxybiphenyl alcohols <b>9</b> and\n<b>10</b>. Mechanistic investigations utilizing product, fluorescence, and nanosecond laser flash photolysis (LFP)\nstudies indicate two distinct pathways for the formation of these BQMs depending upon the functional\ngroups of the progenitor. Formal excited-state intramolecular proton transfer (ESIPT) between the phenol\nand the alkene led to BQMs upon irradiation of the hydroxybiphenyl alkenes <b>7</b> and <b>8</b>, while excited-state\nproton transfer (ESPT) to solvent followed by dehydroxylation was responsible for BQM formation from\nthe hydroxybiphenyl alcohols <b>9</b> and <b>10</b>. Photolysis of <b>7</b> and <b>8</b> in aqueous CH<sub>3</sub>CN gave photohydration\nproducts via attack of water on the respective BQMs, while photolysis of the analogous methyl ethers (of\nthe phenolic moiety) gave only carbocation intermediates. Hydroxybiphenyl alcohols <b>9</b> and <b>10</b> yielded the\ncorresponding photomethanolysis products in aqueous methanol, through attack of CH<sub>3</sub>OH on the respective\nBQMs. Although no evidence was found for BQM formation in LFP studies of <b>8</b> and <b>10</b>, due to its suspected\nshort lifetime, the respective diaryl carbocation (λ<sub>max</sub> 420 nm, τ = 8.5 μs) has been observed upon irradiation\nof <b>8</b> in 2,2,2-trifluoroethanol. A BQM (λ<sub>max</sub> 580 nm) was observed for <b>9</b> but not for <b>10</b>, the latter having\nmore complex chemistry on laser excitation, resulting in a transient that appears to mask any BQM\nabsorption. Significant quenching of fluorescence from the hydroxybiphenyl alkenes at low water content\nimplies that H<sub>2</sub>O is directly involved in reaction from the singlet excited state. The decrease in fluorescence\nintensity of <b>8</b> was found to depend on [H<sub>2</sub>O]<sup>3</sup>; however, the distance required for ESIPT in these systems\nis too large to be bridged by a water trimer. The nonlinear quenching has been attributed to deprotonation\nof the phenol by two water molecules, with concerted protonation at the alkene by another molecule of\nwater. Fluorescence quenching of the hydroxybiphenyl alcohols required much higher water content, implying\na different mechanism of reaction, consistent with the proposal of ESPT (to solvent water) followed by\ndehydroxylation.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 |
| 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) | 0.012 | 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".