Driving t-Butyl Axial: The Effect of Small Spirocyclic Rings on A-Values
Bibliographic record
Abstract
The presence of a small spirocyclic ring at an adjacent position alters the conformational preference for equatorial substitution in cyclohexane and piperidine rings. DFT and low-temperature 1H NMR experiments demonstrate that alkyl groups larger than methyl possess negative A-values when geminal to a spirocyclohexane. Similar observations are made for halogen and other electron withdrawing substituents. For small groups such as methyl and hydroxy, the A-value is near zero, while for groups such as amino, acetamido and aryl, the A-values are positive, but significantly smaller than for simple cyclohexanes. Similar effects are observed for other strained rings (epoxide, cyclobutane, ox-etane) and the concepts extend to acyclic models. The origin of the effect is traced to an increase in torsional strain in combination with hyperconjugative effects in the case of electron poor groups.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| 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".