Kinetic stabilizing effect of the 4-<i>N</i>-methylacetamido substituent on the phenylnitrenium ion
Why this work is in the frame
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Bibliographic record
Abstract
Photolysis of 4-(N-methylacetamido)phenyl azide in aqueous solution results in quantitative formation of the 4-(N-methylacetamido)phenylnitrenium ion, this cation arising from solvent protonation of an initially formed singlet arylnitrene. The cation is observed by flash photolysis, and is identified through characteristic quenching by azide ion and by 2'-deoxyguanosine, both excellent nucleophiles for arylnitrenium ions in water. The nitrenium ion is protonated in acidic solutions to form the 4-(N-methylacetamido)aniline dication, whose pK a is determined to be 1.5 based on the ratepH profile. This means that the nitrenium ion is relatively basic, which suggests that there is significant positive charge on the N-methylacetamido group. Further evidence for this is seen in the remarkably long lifetime (5 ms) of the nitrenium ion in water. In fact, the 4-(N-methylacetamido)phenylnitrenium ion is 5000-fold longer-lived than the 4-methoxy-substituted analog. A 4-methoxy substituent on a phenyl ring is more electron donating according to σ + values (0.78 for MeO vs. 0.60 for NMeAc). The dramatic reversal in the arylnitrenium ions is another example of the failure of these to follow the carbocation scale.Key words: nitrenium ion, flash photolysis, amide substituent.
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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 | 0.001 |
| 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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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 it