Deconstruction of Taft's σ* parameter: QSAR meets QALE
Why this work is in the frame
A frame that forgets how it found something cannot be audited. These are the routes that admitted this work.
Bibliographic record
Abstract
Abstract Taft's σ* parameter has been mostly disregarded in QSAR (quantitative structure–activity relationships) analyses because it appears to reveal only simple field‐inductive substituent effects. However, it can be shown that, when a reference reaction different from that adopted by Taft is used, the σ* values reveal considerably more subtle features. This occurs when a reference reaction parameter, p K a ′ , is used that is closely related to the Brønsted basicity of P‐donor molecules and that is regarded in QALE (quantitative analyses of ligand effects) analyses as measuring the purely σ‐donor properties of the phosphines. Values of Taft's σ* parameter for alkyl groups show an excellent linear correlation with p K a ′ but significant deviations from the correlation increase in the order CH 2 Ph (0.19)<Ph (0.46)< p ‐O‐ i ‐Pr (1.38)<OEt (1.44)<OMe (1.51)<OPh (1.82)<Cl (1.88), and the deviations for the p ‐YC 6 H 4 groups increase linearly with decreasing p K a ′ as Y changes in the order Me 2 N (0.29)<MeO (0.32)<Me (0.39)<F (0.41)<H (0.46)<Cl (0.50)<F 3 C (0.60). The new substituent effects for these ‘deviant’ groups that can be derived from the linear correlations of σ* with p K a ′ are different (even in sign for the p ‐Me 2 NC 6 H 4 group) from the original values of the Taft parameter, and they are much smaller than the additional effects detected here. These results show that σ* values contain within themselves a variety of new features that should be compared with those shown by parameters used in more recent QSAR analyses, and that might be useful in such analyses. Copyright © 2004 John Wiley & Sons, Ltd.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.001 | 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 it