Absolute rate constants for some reactions of the triethylamine-boryl radical and the borane radical anion
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Bibliographic record
Abstract
Laser flash photolysis (LFP) of di-tert-butyl peroxide or dicumyl peroxide at ambient temperatures in the presence of Et3N→BH3 or BH4− generated the title radicals which were found to have broad, featureless absorptions in the visible region. Rate constants for H-atom abstraction from Et3N→BH3 by cumyloxyl radicals show a small solvent dependence, e.g. 12 × 107 and 2.2 × 107 dm3 mol−1 s−1 in isooctane and acetonitrile, respectively. Rate constants for halogen atom abstraction by Et3N→BH2˙ and BH3˙− from a number of chlorides and bromides were determined by LFP and by competitive kinetics, e.g., for Et3N→BH2˙ + CCl4/PhCH2Cl/CH3(CH2)2Cl, k = 4.4 × 109/1.1 × 107/5.1 × 105 dm3 mol−1 s−1 and for BH3˙− + CCl4/PhCH2Cl, k = 2.0 × 109/3.0 × 107 dm3 mol−1 s−1. Rates of addition of Et3N→BH2˙ to 1- and 1,1-substituted olefins increase dramatically as the electron affinity of the olefin increases, confirming the nucleophilic character of amine-boryl radicals. A comparison of the present results with literature data for the addition of olefins of four nucleophilic carbon-centered radicals proves that Et3N→BH2˙ is by far the most nucleophilic radical for which kinetic data are available. A few rate constants for abstraction of hydrogen from electron-deficient carbon by Et3N→BH2˙ are also reported.
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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 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.002 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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