Theoretical studies of the structural, electronic, and <sup>19</sup>F NMR properties of linear and branched perfluorobutanesulfonate
Bibliographic record
Abstract
The structural and electronic properties of linear and branched perfluorobutanesulfonate (PFBS) in its anionic, acidic, and potassium or sodium salt forms were studied in a polarizable continuum model (PCM) of methanol solvent with the B3LYP functional and the 6-31G(d,p) basis set. The 19F chemical shifts and 19F−19F J-coupling constants were determined in a PCM of methanol solvent with GIAO B3LYP/6-31++G(d,p). The differences in energy, enthalpy, and free energy of the four PFBS isomers were compared. The data indicate that the linear PFBS species is less stable than the branched isomers and the isomer with the tert-butyl-like structure is the most stable. The J-coupling contributions via both a non-Fermi contact mechanism and a long chain of bonds (through-bond) indicate that 19F−19F J-coupling constants are long range in these branched PFBS isomers. The calculated and experimental 19F chemical shifts for the linear PFBS species are in good agreement. In addition, the results obtained establish the similarities between the geometries and electronic and NMR properties of linear PFBS and linear perfluorooctanesulfonate (PFOS).
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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 | 0.001 | 0.001 |
| 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".