Carbon Kinetic Isotope Effects in the Gas Phase Reactions of Light Alkanes and Ethene with the OH Radical at 296 ± 4 K
Bibliographic record
Abstract
The carbon kinetic isotope effects (KIEs) of the room-temperature reactions of several light alkanes and ethene with OH radicals were measured in a 30 L PTFE reaction chamber at ambient pressure using gas chromatography coupled with online combustion and isotope ratio mass spectrometry (GCC−IRMS). For simplicity, KIEs are reported in per mil according to ε (‰) = ( k 12 / k 13 − 1) × 1000. The following average KIEs were obtained, (all in ‰): ethane, 8.57 ± 1.95; propane, 5.46 ± 0.35; n -butane, 5.16 ± 0.67; methylpropane, 8.45 ± 1.49; n -pentane, 2.85 ± 0.79; methylbutane, 2.91 ± 0.43; n -hexane, 2.20 ± 0.07; n -heptane, 1.96 ± 0.26; n -octane, 2.13 ± 0.39; cyclopentane, 1.84 ± 0.13; cyclohexane, 4.46 ± 0.51; methylcyclopentane, 1.77 ± 0.53; ethene, 18.6 ± 2.9. As well, the room-temperature rate constant for the reaction of methylcyclopentane + OH, not previously reported in the literature, was determined using relative rates: (8.6 ± 2.2) × 10 -12 cm 3 molecule -1 s -1, including the estimated 25% uncertainty in the rate constant for cyclopentane + OH. KIE values for propane, n -butane and n -hexane have been reported previously [ J. Geophys. Res. [Atmos.] 2000, 105, 29329]. Our KIE for n -hexane is in agreement with the previous measurement, but our values for propane and n -butane are both higher. The dependence between the KIE and chemical structure is discussed, and a method for estimating unknown carbon KIEs for the reactions of light alkanes with OH radicals is presented. With only one exception, predictions using this method agree within a factor of 2 of the experimental KIE results.
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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".