Gas phase carbon acidity and correlations with aqueous pK~a~ values: A comparison of B3LYP/6-311++G(d,p), Gaussian-4 (G4), and experimental approaches
Bibliographic record
Abstract
Abstract Gas phase standard state (298.15 K, 1 atm) calculations were conducted at the B3LYP/6-311++G(d,p) density functional and the Gaussian-4 (G4) composite method levels of theory to estimate the acidity of various carbon acids. Excellent agreement was found between the G4 gas phase enthalpies and free energies of carbon acid dissociation and corresponding experimental values. The B3LYP/6-311++G(d,p) level of theory displayed a significantly lower accuracy for gas phase acidity prediction, but with similar qualitative trends as the G4 calculations. Good correlations using both theoretical methods were found with corresponding carbon acid aqueous pK~a~ values. However, the pK~a~ prediction accuracy of carbon acids based on correlations with theoretical gas phase acidities appears lower than previously reported. Some carbon acid moieties may be outliers in general aqueous pK~a~ versus gas phase acidity quantitative structure-property relationships (QSPRs), warranting further investigative efforts on broader training sets.
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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 | 0.002 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| 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".