Generation and Dissociation of RCOOCaCl<sub>2</sub><sup>−</sup> and other Carboxylate‐Substituted Superhalogens: CO<sub>2</sub> Capture and Implications for Structure Analysis
Bibliographic record
Abstract
Abstract Carboxylate‐substituted superhalogens of the type RCOOMX2− (M=Mg, Ca, Sr, Ba, Mn, Co, Ni, Zn; X=Cl, Br) are easily accessible in the gas phase by electrospray ionisation. Their collision‐induced dissociation (CID) characteristics have been probed by using ion‐trap and triple‐quadrupole mass analysers with particular emphasis on the behaviour of RCOOCaCl2−‐type ions. In the ion trap these appear to react readily with residual water to yield HOCaCl2− as the hydrolysis product. In the absence of water, a collision‐induced McLafferty‐type rearrangement takes over to produce HCaCl2− with the expulsion of an olefin and CO2. A brief computational analysis using the CBS‐QB3 model chemistry provides a satisfactory rationale for these observations. If complexed with MX2 (M=Mg, Ca, Sr, Ba), long‐chain unsaturated aliphatic carboxylate anions undergo various backbone cleavages upon collision. These lead to structure‐diagnostic olefin losses because the position of the double bonds remains intact. Such cleavages are absent in the bare ion RCOO−. The long‐chain ions RCOOMX2− also produce the intriguing species [CO2]MX2−.. These have been characterised by CID experiments, and theory indicates that they may be viewed as a CO2 molecule captured by the salt anion MX2−.. Finally, it is shown that the CID spectra of RCOOCaCl2− ions derived from all‐trans retinoic acid, a compound of current interest in biochemistry and medicine, show a unique structure‐diagnostic dissociation that may greatly aid its qualitative and quantitative analysis.
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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 | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".