Potentiometric study of equilibrium acidities of some carbon acids in acetonitrile
Bibliographic record
Abstract
The pKa values for 30 C-acids of the type CH·R1·R2·R3 where the R1, R2, and R3 substituents are H, alkyl, and aryl, and the most common electron withdrawing groups used in studies of proton-transfer reaction are given herein. The pKa values have been measured potentiometrically in acetonitrile, using a glass electrode. These values were determined in a buffer solution consisting of a C-acid and its tetrabutylammonium salt, at constant ionic strength (0.001 M), at 25°C. The measurements were done under nitrogen, to prevent oxidation of the anion. The influence of water within the sample of the tetrabutylammonium hydroxide base was negligible. The lowest pKa value of 19.1 was found for bis(4-nitrophenyl)cyanomethane, while the largest pKas that could be measured were limited by the basicity of the hydroxide ion, and did not exceed 28. A satisfactory agreement between spectrophotometric and potentiometric acidities was achieved. Key words: C-acids, pKa values, acetonitrile, potentiometry, proton transfer.
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".