Isomerization and Fragmentation Products of CH<sub>2</sub>Cl<sub>2</sub> and Other Dihalomethanes in Rare-Gas Matrices: An Electron Bombardment Matrix-Isolation FTIR Spectroscopic Study
Bibliographic record
Abstract
Isodihalomethanes have been isolated by electron bombardment of CH 2 Cl 2, CD 2 Cl 2, CH 2 Br 2, or CH 2 ClBr in argon, krypton, or xenon followed by condensation on a 15 K matrix-isolation window. Numerous neutral and ionized decomposition products of dihalomethane ionization were also observed. Irradiation with visible or UV light, isotopic substitution, and previous literature assignments of the matrix-isolated products allow definitive identification of most of the observed product bands in the infrared spectra recorded after electron bombardment matrix-isolation experiments (EBMI). Experiments involving substitution of argon with krypton or xenon gas, mixtures of CH 2 Cl 2 and CH 2 Br 2, rare-gas resonant emission irradiation, and thermodynamic considerations support the proposed mechanism for isomerization of the dihalomethane radical cation in the gas phase. This mechanism involves charge-exchange ionization of dihalomethane followed by gas-phase isomerization, isolation, and stabilization in the solid matrix and subsequent neutralization through electron capture. An upper limit to the barrier for CH 2 Cl 2 •+ to CH 2 ClCl •+ isomerization of 43 kJ mol -1 is deduced following observation of the isodichloromethane product after EBMI of xenon/dichloromethane mixtures. Two isomers of the molecular cation, one resembling the distonic isomer of CH 2 Cl 2 •+ (HClC •+ −ClH) and the other a complex between CH 2 Cl + and a chlorine atom [(CH 2 Cl + )Cl • ] have been distinguished based on their stability with respect to UV−visible light irradiation, their infrared spectra, and published ab initio calculations. Vibrational wavenumbers for isodichloromethane and various other products of dichloromethane EBMI experiments in krypton and xenon matrices are reported for the first time. We propose reasoning for the general observation that ions that have an electron affinity (EA) greater than ∼10.8 eV (the “5 eV rule”) are not observed in argon matrices, but those with EAs less than 10.8 eV are observed.
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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".