A Tandem Mass Spectrometry Study of [C,H <sub>2</sub> ,X <sub>2</sub> ,Si] <sup>+•</sup> Ions (X = H, D, Cl) and the Generation of Their Neutral Counterparts
Bibliographic record
Abstract
Two [Si,C,H 4 ] +• isomers, having similar stabilities and a relatively low barrier for their interconversion, have been separately generated in mass spectrometric experiments. CH 2 SiD 2 +• and D 2 -CH 3 SiH +• ions were produced from the same ionic precursor, namely ionized 1,1-dideutero-silacyclobutane (D 2 -I). Dissociation of the latter in the ion source resulted in the silaethene structure, whereas metastable dissociation gave rise to the dideuterated methylsilylene. Appearance energy measurements confirmed the formation of the two [Si,C,H 2 ,D 2 ] +• isomers, whose heats of formation were estimated to be 1017 and 1038 kJ mol −1 for CH 3 SiH +• and CH 2 SiH 2 +• , respectively. Both ion-source and metastable dissociations of ionized D 2 -I resulted in [Si,C,H 3 ,D] +• and [Si,C,H 4 ] +• ions possessing the methylsilylene structure. The collision-induced dissociation (CID) and neutralization–reionization (NR) mass spectra of CH 2 SiD 2 +• and D 2 -CH 3 SiH +• ions were distinctively different. The characteristic dissociation channel for the CH 2 SiD 2 structure was the loss of CH 2 . Some dissociations of the ionized silaethene involved the formation of the methylsilylene intermediate. However, CH 3 SiH +• ions produced by this isomerization appeared to be unstable and did not survive neutralization–reionization. As a result, the CID mass spectra of CH 2 SiD 2 +• ions prior to neutralization and surviving the NR event were almost identical. Strong recovery signals in the NR mass spectra were consistent with the intrinsic stability of neutral silaethene and methylsilylene. The interconversion of these structures generated by neutralization of their positively-charged counterparts seems to be very unlikely. The CID, NR and NR/CID mass spectra of [Si,C,H 2 ,Cl 2 ] +• ions produced from various precursors and in different time frames were indistinguishable. They corresponded to the CH 2 SiCl 2 connectivity of the atoms. The heat of formation for CH 2 SiCl 2 +• ions was estimated to be ∼732 kJ mol −1 , based on appearance energy measurements. The presence of a strong recovery signal in the NR mass spectra was consistent with the formation of stable neutral 1,1-dichlorosilaethene in the gas phase on the microsecond time frame.
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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) | 0.001 | 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 | 0.001 | 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".