First Direct Observation of Equilibrium Involving Cl Atoms: Cl + C <sub>2</sub> H <sub>4</sub> ⇔ ClCH <sub>2</sub> CH <sub>2</sub> by VUV Monitoring
Bibliographic record
Abstract
High Resolution Image Download MS PowerPoint Slide The kinetics between Cl and ethylene, R1, have been determined between 298 and 822 K in time-resolved experiments, where the Cl atoms were monitored for the first time via laser-induced fluorescence at 118.877 nm. A key advantage of this method of Cl detection is that there is limited absorption of 118 nm radiation by oxygen, and we report the first Cl reactivity measurements. The kinetics of Cl + C 2 H 4 at room temperature are simple association, k 1a([ M ]), and have been used in a master equation analysis (via the MESMER application) to show consistency with most of the literature. Between 393 and 490 K, the kinetics exhibited equilibrium behavior: Cl + C 2 H 4 ⇔ Cl–C 2 H 4 ( k 1a([ M ]), k –1a([ M ]) ). These forward and reverse rate coefficients have been used in van’t Hoff and reaction rate theory (MESMER) analysis to determine the enthalpy of reaction, Δ r H R1a o . This analysis yields a Δ r H 0,R1a o equal to −74.1 ± 0.6 kJ mol –1 . Ab initio structure calculations provided input values for MESMER analysis of the equilibrium data. The range of ab initio calculations carried out returned consistent values for Δ r H 0,R1a o, but the values are consistently more exothermic than the experimental value. Via comparison between theory and experiment, it is estimated that these ab initio calculations are good to ∼4 kJ mol –1 . Above 500 K, the removal kinetics are dominated by abstraction: Cl + C 2 H 4 → HCl + C 2 H 3 ( k 1b ). This reaction occurs on an endothermic potential surface, where the energy of the transition state is below that of the products. Analysis of this kinetic data and the literature highlights that the location of the transition state along the reaction coordinate varies with temperature, becoming more reagent-like with increased temperature.
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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 | 0.000 | 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 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.011 | 0.001 |
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".