Discrimination in the Solid‐State Photodimerization of 1‐Methyl‐5,6‐diphenylpyrazin‐2‐one
Bibliographic record
Abstract
Abstract 1‐Methyl‐ and 1‐ethyl‐5,6‐diphenylpyrazin‐2‐one crystallize in two modifications, one of which is light‐stable and the other light‐sensitive. The light‐sensitive modification is known to undergo photodimerization in the solid state. This polymorph crystallizes in the monoclinic space group P 2 1 with two crystallographically independent molecules in the asymmetric unit. The molecules are packed in stacks running parallel to the unique b axis. The two independent molecules are arranged alternately along the stack. In principle, there are two different pairs of molecules within a stack that can undergo photodimerization, and each should form a different enantiomer. A large crystal was irradiated and a solution of the product was separated by HPLC. The optical purity of the (+)‐enantiomer sample was estimated to be greater than 90 %. This finding indicates that only one of the two pairs undergoes photoreaction. The structure of a single crystal of the pyrazinone was elucidated by X‐ray diffractometry before and after irradiation with a laser at a wavelength of 488 nm to 19 % conversion. The results of the crystal‐structure determinations provide additional evidence that only one of the two pairs of molecules undergoes photodimeri‐zation although there are no significant differences between the distances between the reacting centers. Furthermore, the latter results suggest that weak hydrogen bonds are a dominant factor that determines which of the two pairs is dimerized upon irradiation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
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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".