Kinetics of C<sub>2</sub>H Reactions with Hydrocarbons and Nitriles in the 104−296 K Temperature Range
Bibliographic record
Abstract
Reactions of C 2 H with isobutane ( k 1 ), 1-butene ( k 2 ), isobutylene ( k 3 ), 1,3-butadiene ( k 4 ), methyl cyanide ( k 5 ), ethyl cyanide ( k 6 ), and propyl cyanide ( k 7 ) are studied at low temperature using a pulsed Laval nozzle apparatus. The C 2 H radical is prepared by 193-nm photolysis of acetylene, and the C 2 H concentration is monitored using CH(A 2 Δ) chemiluminescence from the C 2 H + O 2 reaction. The rate constants at low and high temperatures are k 1 = (1.3 ± 0.3) × 10 -10 and (1.0 ± 0.2) × 10 -10 for isobutane, k 2 = (2.1 ± 0.4) × 10 -10 and (2.2 ± 0.4) × 10 -10 for 1-butene, k 3 = (1.4 ± 0.3) × 10 -10 and (1.2 ± 0.2) × 10 -10 for isobutylene, and k 4 = (2.9 ± 0.6) × 10 -10 and (3.3 ± 0.6) × 10 -10 for 1,3-butadiene at T = 104 and 296 K, respectively (in units of cm 3 molecule -1 s -1 ). Comparison with existing data shows a trend of a decrease in activation energy with increasing size of the hydrocarbon chain. For these reactions of hydrocarbons containing four carbon atoms, the activation energy is zero within experimental uncertainty, and the rate constants do not depend on temperature in the 104−296 K temperature range. The rate constants for C 2 H reactions with methyl cyanide, ethyl cyanide, and propyl cyanide are measured at three temperatures, 104, 165, and 298 K. Measured rate constants are fit to an Arrhenius expression and are k 5 = (1.8 ± 0.35) × 10 -11 exp(−766 ± 38/ T ), k 6 = (1.5 ± 0.3) × 10 -11 exp(−145 ± 10/ T ), and k 7 = (2.1 ± 0.4) × 10 -11 exp(−51 ± 4/ T ) (in units of cm 3 molecule -1 s -1, T is in Kelvin). At T = 296 K, k 3, k 5, k 6, and k 7 are measured as a function of total pressure and show no pressure dependence in the 0.6−8 Torr (0.08−1.07 kPa) pressure range. Results from this work are compared with the results of previous investigations of C 2 H reactions at low temperature and are discussed in relation to the atmospheres of Saturn and Titan.
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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 | 0.000 |
| 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) | 0.003 | 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".