Azabenzenes (azines) The nitrogen derivatives of benzene with one to six N atoms: Stability, homodesmotic stabilization energy, electron distribution, and magnetic ring current; a computational study
Bibliographic record
Abstract
The twelve azabenzenes the species formed by replacing CH groups of benzene by N were examined computationally (with emphasis on the six contiguous-nitrogen species). MP2(fc)/6-31G*, B3LYP/6-31G*, CCSD(T)/6-31G*//MP2(fc)/6-31G*, and G3(MP2) calculations were used to probe kinetic and thermodynamic stabilities, homodesmotic ring-opening energies, electron distribution (bond orders and lengths, Bird index), and NICS values, primarily to discern where the transition occurs from reasonably stable to highly fragile species. Some azabenzenes with three and those with four or more nitrogens are thermodynamically unstable, but kinetic stabilities indicated that, with the possible exception of hexaazabenzene, all the azabenzenes should be isolable, although some with four nitrogens might decompose at room temperature, and pentaazabenzene would require matrix isolation techniques. Although homodesmotic ring-opening reactions showed an almost monotonic decrease in the stability of the cyclic relative to the open-chain species (in appropriate ring-opening reactions) on going from benzene to hexaazabenzene, bond-order variation and NICS suggested this may be because of increasing destabilization by nitrogen lone pairs rather than because of a decrease in electron delocalization (in aromaticity). Key words: azines, azabenzenes, pentazine, hexazine, ab initio, DFT, aromaticity.
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".