Hydrogen Atom Abstraction from Polyolefins: Experimental and Computational Studies of Model Systems
Bibliographic record
Abstract
The hydrogen atom transfer reactions that underlie peroxide-initiated modifications of polyolefin architectures and ambient-temperature air oxidations are examined through a combination of experiments and quantum chemical calculations on model hydrocarbons. The regioselectivity of H-atom from pentane, 2,4-dimethylpentane, and 2,2,4,4-tetramethylpentane to t-BuO• generated from tert-butyl hyponitrite at 25 °C was quantified by trapping of the alkyl radicals with a UV-active nitroxide. The data show that hydrocarbon reactivity toward t-BuO• does follow neither well-established trends in homolytic C–H bond dissociation energy (tertiary > secondary > primary) nor trends in the susceptibility of polyolefins to autoxidation. These experiments, together with quantum chemical calculations conducted at the CBS-QB3 level of theory, reveal the importance of entropic effects in these exergonic H-atom transfer processes. In contrast, the endergonic nature of H-atom abstraction by t-BuOO• produces conventional hydrocarbon reactivity patterns, as enthalpic contributions to transition-state energies are dominant. These findings bring clarity to the structure/reactivity relationships of polyolefins in the field of radical chemistry.
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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) | 0.000 | 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".