The Mandelamide Keto−Enol System in Aqueous Solution. Generation of the Enol by Hydration of Phenylcarbamoylcarbene
Bibliographic record
Abstract
Flash photolysis of diazophenylacetamide in aqueous solution produced phenylcarbamoylcarbene, whose hydration generated a transient species that was identified as the enol isomer of mandelamide. This assignment is based on product identification and the shape of the rate profile for decay of the enol transient, through ketonization to its carbonyl isomer, as well as by the form of acid-base catalysis of and solvent isotope effects on the decay reaction. Rates of enolization of mandelamide were also determined, by monitoring hydrogen exchange at its benzylic position, and these, in combination with the ketonization rate measurements, gave the keto-enol equilibrium constant pK(E) = 15.88, the acidity constant of the enol ionizing as an oxygen acid, pQ(E)(a)= 8.40, and the acidity constant of the amide ionizing as a carbon acid pQ(K)(a)= 24.29. (These acidity constants are concentration quotients applicable at ionic strength = 0.10 M.) These results show the enol content and carbon acid strength of mandelamide, like those of mandelic acid and methyl mandelate, to be orders of magnitude less than those of simple aldehydes and ketones; this difference can be attributed to resonance stabilization of the keto isomers of mandelic acid and its ester and amide derivatives, through electron delocalization into their carbonyl groups from the oxygen and nitrogen substituents adjacent to these groups. The enol of mandelamide, on the other hand, again like the enols of mandelic acid and methyl mandelate, is a substantially stronger acid than the enols of simple aldehydes and ketones. This difference can be attributed to the electronegative nature of the oxygen and nitrogen substituents geminal to the enol hydroxyl group in the enols of mandelic acid and its derivatives; in support of this, the acidity constants of these enols correlate well with field substituent constants of these geminal groups.
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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 | 0.001 |
| 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 | 0.001 |
| 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".