On the generation of oxirene and dimethyloxirene by retro-DielsAlder reactions, and reactions of dimethyloxirene: a computational study
Bibliographic record
Abstract
The isomerization of oxirene (oxacyclopropene) (1) to ketene, dimethyloxirene (7) to dimethylketene via the oxo carbene ("ketocarbene"), and the retro-DielsAlder extrusion of oxirene and dimethyloxirene from their formal adducts (9 and 24, respectively) with benzene were studied computationally. All species were optimized at the MP2(fc)/631G(df,p) level; the species involving 1 were also subjected to MP2(fc)/631G(df,p) frequency and single-point CCSD(T)/631G(df,p) calculations. At the CCSD(T)/631G(df,p)//MP2(fc)/631G(df,p) level 1 isomerized to ketene in one step with a barrier of 2.8 kJ mol1 and a reaction energy of 320.6 kJ mol1. The extrusion of 1 from 9 had a late transition state and activation and reaction energies of 264.2 and 214.2 kJ mol1, respectively, cf. cyclopropene extrusion from its adduct (192.3 and 95.9 kJ mol1), indicating an antiaromatic destabilization energy of 214.2 95.9 = 118 kJ mol1 for 1. The carbene 8 from ring-opening of 7 lay 10.9 kJ mol1 above 7 (CCSD(T)/631G(df,p)//MP2(fc)/631G(df,p)), but the transition state could not be found; 8 isomerized to dimethylketene (252.7 kJ mol1 below 7) with a barrier of 16.4 kJ mol1, and to s-(Z)- and s-(E)-butenone with barriers of 28.5 and 35.4 kJ mol1, respectively. The UV (TDDFT, B3P86/6311++G**//MP2(fc)/631G(df,p)) spectra of 1 and 7 were calculated. Discrepancies were seen between the calculated IR spectra of 7 (bis(trifluoromethyl)oxirene) and perfluoro ethyl methyloxirene, and those attributed to these species in earlier matrix-isolation work. Key words: oxirene, dimethyloxirene, ab initio, retro-DielsAlder, DielsAlder.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 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".