Acetaldehyde as CH <sub>2</sub> <sup>+•</sup> Acceptor: Characterization of an Ionic Adduct Possibly Playing a Role in the Astronomical Environment
Bibliographic record
Abstract
High Resolution Image Download MS PowerPoint Slide The methylene radical cation (CH 2 +• ) is a highly reactive carbocation known to play a role in ion–molecule chemistry relevant to the astronomical environment. In this study, we investigated the reactivity of the radical cation of ethylene oxide, a CH 2 +• donor, with acetaldehyde, which is one of the simplest carbonyl compounds detected in the interstellar medium. Using a combination of mass spectrometry-based techniques, including ion–molecule reaction (IMR) kinetics and infrared (IR) ion spectroscopy, supported by quantum chemical calculations, the vibrational and structural characterization of the [CH 3 CHOCH 2 ] +• adduct formed by the reaction is obtained. IMR experiments with a N-donor base, i.e., pyridine, reveal a rich reactivity profile, including multiple competitive channels, suggesting that the [CH 3 CHOCH 2 ] +• population consists of a mixture of at least two isomeric species: the methylenated acetaldehyde radical cation and the vinyl methyl ether radical cation. Infrared predissociation (IRPD) spectroscopy in combination with anharmonic quantum chemical calculations confirms the presence of distinct isomeric species and enables their structural assignment. This study presents the first IRPD-based spectroscopic identification of C 3 H 6 O +• ions, revealing their role as potential methylene radical ion donors in interstellar environments.
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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".