Decarboxylation without CO<sub>2</sub>: Why Bicarbonate Forms Directly as Trichloroacetate Is Converted to Chloroform
Bibliographic record
Abstract
Patterns in the observed catalysis of decarboxylation reactions required us to conclude that these reactions involve initial hydration of the carboxylate and subsequent loss of bicarbonate. This raises the important and general question of why CO2 is not formed directly. Reaction profiles for the direct decarboxylation of trichloroacetate were generated with DFT calculations and show no significant barrier to the recombination of the incipient trichloromethide and CO2. In contrast, cleavage of the C-C bond from the hydrated intermediate shows a substantial barrier to recombination that allows separation of the products. The free energy of the transition state for C-C bond cleavage following hydration is higher than the free energy for formation of the hydrate and is comparable to the free energy of activation for direct decarboxylation. Thus, we conclude that the advantage of the hydrolytic pathway is that it provides a means to overcome the problems of separation and solvation that hinder the direct loss of CO2. The resulting concepts are readily extended to explicating the mechanisms of processes in enzymic catalysis as well as providing a basis for producing C-C bonds by the addition of derivatives of carbanions to carbonates.
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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 | 0.001 |
| 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 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".