Rotational spectra of four of the five conformers of 1-pentene
Bibliographic record
Abstract
The rotational spectra of four of the five expected conformers of 1-pentene, together with their monosubstituted 13C isotopic forms, have been measured in a molecular beam using a pulsed-nozzle Fourier-transform microwave spectrometer. One of the conformers has Cs point-group symmetry while the other three conformers have C1 point-group symmetry. The measurements are compared to results from molecular modeling calculations using the MM3 molecular-mechanics force field of Allinger et al. and to ab initio electronic structure calculations (MP2/6-31G*, MP2/6-311G*, MP4/6-31G*, MP4/6-311G*). Both types of calculations suggest the existence of five distinct conformers of 1-pentene, four of C1 symmetry and one of Cs symmetry. Both the MM3 and ab initio rotational constants deviate from the measured values by ⩽5%. The relatively high barriers between the four conformers limit the conformational cooling in the expansion, allowing all four conformers to be observed at the <2 K rotational temperature of the molecular beam. Efforts to identify the fifth conformer were unsuccessful, presumably due to its reduced intensity, which makes it difficult to identify its spectral pattern from among the plethora of weak unassigned lines due to impurities, complexes, and possible vibrationally excited conformers. The fifth conformer is predicted to have the highest energy of the five conformers of 1-pentene, as well as a low-energy barrier (109 cm−1 at MP2/6-311G* level) for conformational isomerization.
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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) | 0.002 | 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".