Carboxylic Acids as Lewis Bases: Structures and Properties of Strongly Acidic Carboxylic Acid Adducts of B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>
Bibliographic record
Abstract
Carboxylic acids react with B(C 6 F 5 ) 3 in CH 2 Cl 2 to form 1:1 adducts, which have been characterized by room-temperature IR and low-temperature (−30 °C) 1 H, 19 F, 13 C, and 11 B NMR spectroscopy. Coordination appears to occur via the carbonyl oxygen atom, and exchange between an adduct and its components is generally sufficiently slow that 1 H, 19 F, 13 C, and 11 B resonances of the adduct are readily distinguished from the 1 H and 13 C resonances of the corresponding free acid and the 19 F and 11 B resonances of free B(C 6 F 5 ) 3 . The electron-withdrawing power of the highly electrophilic B(C 6 F 5 ) 3 increases the Brønsted acidity of the coordinated carboxylic acids sufficiently that they are able to protonate isobutene and thus initiate its carbocationic polymerization. The enhanced acidity also results in slow, partial cleavage of B−C 6 F 5 bonds, and with benzoic acid the compound [(μ-C 6 H 5 CO 2 )(μ-OH){B(C 6 F 5 ) 2 } 2 ] has been isolated and characterized crystallographically. Because of slow B−C 6 F 5 cleavage, crystallographically useful crystals of a 1:1 adduct of a carboxylic acid have not been obtained, but C 2 H 5 CO 2 Me·B(C 6 F 5 ) 3, the 1:1 adduct of methyl propionate, has for purposes of comparison been prepared and characterized spectroscopically and crystallographically. In this case coordination occurs unequivocally via the carbonyl oxygen atom.
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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 | 0.000 | 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) | 0.002 | 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".