Chlorine atom initiated reactions of selected tropospheric halocarbons — Kinetic and product studies
Bibliographic record
Abstract
Halogens are suggested as important atmospheric oxidants in the marine boundary layer. The room-temperature kinetics of the chlorine-initiated reactions of three biogenic brominated hydrocarbons and four anthropogenic chlorinated ethenes was investigated by gas chromatography with flame ionization detection (GC–FID) at a pressure of 1 atm (1 atm = 101.325 kPa) in air, using the relative rate technique. The rate constants (× 1013 cm3 molecule–1 s–1) for CH2Br2, CHBr2Cl, and CHBr3 reactions at 298 ± 2 K were found to be 4.25 ± 0.65, 2.03 ± 0.31, and 2.81 ± 0.41, respectively, using methane as a reference compound. Room temperature rate constants (±1011 cm3 molecule–1 s–1) obtained for 1,1-dichloroethene, cis-dichloroethene, trans-dichloroethene, and trichloroethene using ethene as a reference are 13.4 ± 3.3, 9.1 ± 2.3, 7.4 ± 1.8, and 7.7 ± 1.9, respectively. The rate constants of chlorine-atom reactions with various hydrocarbons obtained in this work and taken from literature were correlated with corresponding rate constants of the OH radical available in the literature. The temperature dependences for the reactions of chlorine atoms with chlorinated ethenes were studied within the 298–358 K range. The corresponding Arrhenius expressions for the rate constants are (cm3 molecule–1 s–1): ln k = (–25.26 ± 0.17) – (758 ± 55)/T for 1,1-dichloroethene, ln k = (–25.79 ± 0.10) – (799 ± 34)/T for cis-dichloroethene, ln k = (–26.74 ± 0.09) – (1018 ± 28)/T for trans-dichloroethene, and ln k = (–26.10 ± 0.26) – (846 ± 83)/T for trichloroethene. In addition, product studies for the chlorine-initiated gas phase oxidation reactions of CHBr3 and CHBr2Cl were performed using gas chromatography with mass spectrometric detection (GC–MS). The only identified product for the reaction of CHBr3 with Cl reaction was COBr2, while for the CHBr2Cl + Cl reaction, COBrCl and COCl2 were observed, indicating the possibility of halogen atom release. The atmospheric implications of the results obtained are discussed.Key words: tropospheric reactions, kinetics, chlorine atoms, chlorinated hydrocarbons, brominated hydrocarbons.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".