Valence bond calculations on the transition state for the E2 reaction of fluoride ion with ethyl fluoride Implications for the More O'Ferrall Jencks diagram
Bibliographic record
Abstract
A valence bond self-consistent field (VBSCF) calculation has been carried out on the bimolecular elimination (E2) reaction of fluoride ion with ethyl fluoride. The transition state was first optimized at HF/6-31+G and the resulting orbitals were used in the VBSCF calculation. A transition-state hybrid consisting of four structures (FH-CH2-CH2-F, F-HCH2=CH2F, F-HCH2-CH2-F, and FH-CH2-CH2+F) failed to give a reasonable energy. Incorporation of four charge-separated structures (FH+CH2-CH2-F, FH+CH2-CH2+F, FH+CH2=CH2F, and F-HCH2-CH2+F) for a total of eight resulted in an energy slightly below HartreeFock. A full-space VBSCF calculation utilizing 50 structures showed that the eight structures give a sufficiently accurate wave function. The transition state is dominated by charge-separated structures, leading to a greater degree of charge separation than in either the reactant or product complex. Therefore, the transition state does not evolve synchronously from the reactants, and explicit allowance should be made for this fact when applying descriptions of the reaction path, such as that in the More O'Ferrall Jencks diagram. Key words: elimination reaction, E2, transition state, VBSCF calculation, XMVB programs.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| 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".