Direct Experimental Determination of the Energy Barriers for Methyl Cation Transfer in the Reactions of Methanol with Protonated Methanol, Protonated Acetonitrile, and Protonated Acetaldehyde: A Low Pressure FTICR Study
Bibliographic record
Abstract
Methyl cation transfer reactions between methanol and protonated methanol, protonated acetonitrile, and protonated acetaldehyde have been investigated experimentally by low-pressure FT-ICR mass spectrometry. The temperature dependencies of the rate constants for these reactions were determined in an Arrhenius-type analysis to obtain activation energies, enthalpies, and entropies of activation. The enthalpies of activation were determined to be −16.9 ± 0.6, −16.5 ± 0.6, and −18.4 ± 0.7 kJ mol -1 for the methanol/protonated methanol, methanol/protonated acetonitrile, and methanol/protonated acetaldehyde reactions, respectively. These values agree quite well with ab initio-calculated values. The entropies of activation were found to be quite similar for all three reactions within experimental uncertainty, which is expected due to the similar transition-state structures for all reactions. Ab initio potential energy surfaces calculated at the MP2/6-311G** level and basis set are reported for the three reactions. For the methanol/protonated acetonitrile and methanol/protonated acetaldehyde reactions, isomerization of the initially produced proton-bound dimer to a methyl-bound complex is suggested prior to methyl cation transfer. The barrier for the first isomerization is predicted to be significantly lower than the barrier for methyl cation transfer such that it does not interfere with the experimental determination of the latter.
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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 | 0.000 |
| 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) | 0.000 | 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".