Kinetic Isotope Effect for Hydrogen Abstraction by <sup>•</sup>OH Radicals from Normal and Carbon-Deuterated Ethyl Alcohol and Methylamine in Aqueous Solutions
Bibliographic record
Abstract
Selective H/D kinetic isotope effects (KIEs) have been determined for the various routes by which • OH radicals react with ethanol (CH 3 CH 2 OH and CD 3 CD 2 OH) and methylamine (CH 3 NH 2 and CD 3 NH 2 ) in H 2 O solutions. The KIEs have been evaluated from overall rate constants and the yields in which the individual primary radicals were generated in the • OH reaction with these compounds. The analytical method applied for the yield determinations was redox titration with suitable scavengers, namely, methyl viologen and Fe(CN) 6 3- for the reducing radicals (CH 3 C • HOH/CD 3 C • DOH and • CH 2 NH 2 / • CD 2 NH 2 ) and I - and hydroquinone for the oxidizing radicals (CH 3 CH 2 O • /CD 3 CD 2 O • and • NHCH 3 / • NHCD 3 ). The numerical results obtained also include, besides yields relative to total available • OH, absolute rate constants for most of these scavenging reactions. For the alcohol, the major process (almost 90%) is H/D abstraction from the C α bond with KIE = 1.96. For methylamine, abstraction from C α H/D occurs with only 37% (H) and 26% (D) but at a similar KIE = 1.86. The remainder, denoting the major process in this case,accounts for the formation of aminyl radicals. The secondary KIEs for N−H cleavage, and O−H cleavage in the case of the alcohol, are close to unity, reflecting the expected negligible influence of C−H/D substitution in the attached alkyl groups. Abstraction ofβ-C-attached H/D in ethanol shows, also in qualitative agreement with expectation, a larger KIE = 3.4 than that for α-C H/D. An interestingly high KIE ≈ 50 was obtained for the 1,2 hydrogen shift that converts the CH 3 CH 2 O • and CD 3 CD 2 O • oxyl radicals into the corresponding α-hydroxyethyl radicals CH 3 C • HOH and CD 3 C • DOH. All of the results are discussed in light of existing literature data on relevant H/D isotope effects, the influence of solvent relative to gas phase, the selectivity of the • OH attack, and other mechanistic considerations. Specifically, the mechanism by which the • OH reacts with the amine seems likely to involve a transient, caged aminium/hydroxide ion pair.
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.
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 | 0.001 | 0.001 |
| 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) | 0.000 | 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".