Steric Demand and Rate‐determining Step for Photoenolization of Di‐<i>ortho</i>‐substituted Acetophenone Derivatives
Bibliographic record
Abstract
Abstract Laser flash photolysis of ketone 1 in argon‐saturated methanol yields triplet biradical 1BR ( τ = 63 ns) that intersystem crosses to form photoenols Z ‐1P ( λ max = 350 nm, τ ~ 10 μs) and E ‐1P ( λ max = 350 nm, τ > 6 ms). The activation barrier for Z ‐1P re‐forming ketone 1 through a 1,5‐H shift was determined as 7.7 ± 0.3 kcal mol −1 . In contrast, for ketone 2, which has a less sterically hindered carbonyl moiety, laser flash photolysis in argon‐saturated methanol revealed the formation of biradical 2 BR ( λ max = 330 nm, τ ~ 303 ns) that intersystem crosses to form photoenol E ‐2P ( λ max = 350 nm, τ > 42 μs), but photoenol Z ‐2P was not detected. However, in more viscous basic H‐bond acceptor ( BHA ) solvent, such as hexamethylphosphoramide, triplet 2 BR intersystem crosses to form both Z ‐2P ( λ max = 370 nm, τ ~ 1.5 μs) and E ‐2P. Thus, laser flash photolysis of ketone 2 in methanol reveals that intersystem crossing from 2 BR to form Z ‐2P is slower than the 1,5‐H shift of Z‐2P, whereas in viscous BHA solvents, the 1,5‐H shift becomes slower than the intersystem crossing from 2 BR to Z‐2P. Density functional theory and coupled cluster calculations were performed to support the reaction mechanisms for photoenolization of ketones 1 and 2 .
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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) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| 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".