The Gas-phase Reaction of NH<sub>2</sub> with Formaldehyde (CH<sub>2</sub>O) is not a Source of Formamide (NH<sub>2</sub>CHO) in Interstellar Environments
Bibliographic record
Abstract
Abstract The first experimental study of the low-temperature kinetics of the gas-phase reaction of NH 2 with formaldehyde (CH 2 O) has been performed. This reaction has previously been suggested as a source of formamide (NH 2 CHO) in interstellar environments. A pulsed Laval nozzle equipped with laser-flash photolysis and laser-induced fluorescence spectroscopy was used to create and monitor the temporal decay of NH 2 in the presence of CH 2 O. No loss of NH 2 could be observed via reaction with CH 2 O, and we place an upper limit on the rate coefficient of <6 × 10 −12 cm 3 molecule −1 s −1 at 34 K. Ab initio calculations of the potential energy surface were combined with Rice–Rampsberger–Kassel–Marcus (RRKM) calculations to predict a rate coefficient of 6.2 × 10 −14 cm 3 molecule −1 s −1 at 35 K, consistent with the experimental results. The presence of a significant barrier, 18 kJ mol −1 , for the formation of formamide as a product, means that only the H-abstraction channel producing NH 3 + CHO, in which the transfer of an H atom can occur by quantum mechanical tunneling through a 23 kJ mol −1 barrier, is open at low temperatures. These results are in contrast with a recent theoretical study, which suggested that the reaction could proceed without a barrier and was therefore a viable route to gas-phase formamide formation. The calculated rate coefficients were used in an astrochemical model, which demonstrated that this reaction produces only negligible amounts of gas-phase formamide under interstellar and circumstellar conditions. The reaction of NH 2 with CH 2 O is therefore not an important source of formamide at low temperatures in interstellar environments.
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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) | 0.001 | 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".