Vapor Pressures of the Fluorinated Telomer AlcoholsLimitations of Estimation Methods
Bibliographic record
Abstract
The influence of the unique, physical properties of poly- and perfluorinated chemicals on vapor pressure was investigated. Vapor pressures of a suite of fluorinated telomer alcohols (FTOHs) (CF3(CF2)nCH2CH2OH, where n = 3, 5, 7, or 9) were measured using the boiling point method and ranged from 144 to 992 Pa. Comparison of experimental and literature values indicate that perfluorocarbons (CF3(CF2)nCF3, where n = 0-6) and fluorinated telomer alcohols have vapor pressures equal to or greater than that of their hydrogen analogues. These chemically counterintuitive results can be explained by the unique geometry of poly- and perfluorinated chemicals--in particular the stiff, helical perfluorinated chain and the significant intramolecular hydrogen bonding of the FTOHs. The majority of models investigated for the estimation of vapor pressure did not compensate for this unique geometry and consistently underpredicted the vapor pressures of the FTOHs. Calculation of partitioning constants using both experimental and estimated vapor pressures indicate that both the Antoine and Modified Grain models, and to a lesser degree the Mackay model, are insufficiently accurate for estimating the vapor pressures of the FTOHs, particularly the longer chain FTOHs. Future models should consider parameters such as geometry, strength, and location of intramolecular hydrogen bonds and otherfunction groups in the molecule in order to improve vapor pressure estimation accuracy. It appears likely that the unique molecular geometry of the FTOHs influences not only their vapor pressure but also other physical properties and hence environmental fate and dissemination.
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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 | 0.001 | 0.004 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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".