Oxide Radical Anion Reactivity with Aliphatic Amino Compounds in Aqueous Solution: Comparison of H−Atom Abstraction from C−H and N−H Groups by <sup>•</sup>O<sup>-</sup> and <sup>•</sup>OH Radicals
Bibliographic record
Abstract
One-electron oxidants react with H 2 N−CHRR‘ amino compounds by electron transfer (ET), and direct H abstraction from N−H and C−H, giving respectively, aminium ( +• NH 2 CHRR‘), aminyl ( • NH−CHRR‘), and α-C-centered radicals (H 2 N- • CRR‘). The yields of these species from • O - reactions with the anions of glycine (Gly - ), alanine (Ala - ), and α-methylalanine (MeAla - ) and with methylamine (MeNH 2 ) have been investigated at pH ≥ 13. The results indicate an ET process is negligible. Aminyl and α-C-centered radicals appear to be formed only by direct H abstraction reactions. In line with this, the ratios of the overall rates of H abstraction from N−H and C−H, k N( - H • ) / k C( - H • ), for • O - reacting with different amino compounds decrease with C−H bond dissociation enthalpy (BDE) and thus follow the pattern expected for direct abstraction reactions. In contrast to • O -, the conjugate • OH radical produces significant yields of aminium radicals by ET, which evidently contribute to aminyl radical formation by subsequent proton loss from nitrogen. Thus, the k N( - H • ) / k C( - H • ) ratios for • OH are higher than those for • O - and do not decrease regularly with C−H BDE. Formation of α-C-centered radicals via ET and subsequent proton loss from a C−H group of the aminium radical is much less likely. The overall rates of H abstraction from C−H sites by both • OH and • O - are found to increase with the exothermicity of the reaction. Because of its spherical symmetry the steric factors for • O - reactions are larger than those for • OH, but in most cases this appears to be compensated by more favorable potential energy surfaces stemming from the 36 kJ mol -1 greater exothermicity of • OH reactions. • O - reactions with charged species are of course also susceptible to the effects of Coulombic interactions.
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How this classification was reachedexpand
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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.002 |
| 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, 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".