Carbonate, carbamate, urea, and guanidine as model species for functional groups in biological molecules A combined density functional theory and mass spectrometry examination of polysodiation and gas-phase dissociation
Bibliographic record
Abstract
Electrospray mass spectrometric analyses of carbonate, carbamate, urea, and guanidine in the presence of sodium ions results in polysodiated complexes of the type, [M (n 1)H + nNa]+, where M is the species analyzed and n = 2 and (or) 3. These complexes are unusual in their high sodium contents and their attractive structures. The [M H + 2Na]+ complexes fragment to produce [Na2NH2]+, Na+, and a product ion resulting from the loss of NH3. The [M 2H + 3Na]+ complexes dissociate to give a number of fragment ions, including [Na3O]+, [Na2OH]+, [NaOCNNa]+, [Na2NH2]+, [Na3CN2]+, and Na+, depending on the elemental composition of M. These dissociation reactions were examined both experimentally by mass spectrometry and theoretically by density functional theory. Reaction profiles as calculated at B3LYP/6-311G** for disodiated carabamate, urea, and guanidine, and for all the bases in trisodiated form are given. Both experimental and theory show [Na3CO3]+ to have high stability towards collisional activation and to preferentially dissociate to give [Na3O]+ and CO2, rather than Na+ and Na2CO3.Key words: carbonate, carbamate, urea, guanidine, electrospray, collision-induced dissociation, density functional theory, sodium ion binding energies.
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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".