Cover Picture: Hydrogen–Hydrogen Bonding: A Stabilizing Interaction in Molecules and Crystals (Chem. Eur. J. 9/2003)
Why this work is in the frame
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Bibliographic record
Abstract
Abstract The cover picture shows a schematic representation of the change in structure accompanying the planarization of biphenyl through the formation of bond paths between the pairs of ortho ‐hydrogen atoms. The top figure for the twisted equilibrium structure portrays four of the rings of hydrogen atoms, each shown as a spatial region defined by the intersection of its C|H interatomic surface with the van der Waals surface defined by the 0.001 au electron density envelope, the surfaces for the pairs of ortho ‐hydrogen atoms touching at the geometry of the equilibrium structure. Planarization results in a lengthening of the CC separation between the rings by ∼0.01 Å, and the ortho ‐hydrogen atoms are brought to separations ∼0.04 Å less than twice their van der Waals radii. The resulting increase in the energy of the carbon atoms is, however, largely negated by HH bonding, that is, the formation of an interatomic surface and an associated bond path linking each pair of ortho ‐hydrogen atoms. Thus the ortho ‐hydrogen atoms in planar biphenyl do not experience “steric nonbonded repulsions”, but rather, like all interactions denoted by a bond path, make a stabilizing contribution to the energy of ∼10 kcal mol −1 per HH interaction. HH bonding is present between the corresponding hydrogen atoms in polybenzenoids, such as phenanthrene and chrysene, and it is the presence of such interactions between the hydrogens of methyl groups in neighboring tetra‐ tert ‐butyl groups that encapsulate and stabilize the otherwise unstable tetrahedrane and cyclobutadiene molecules. For further details see the article by R. F. W. Bader et al. on p. 1940 ff.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| 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 | 0.004 |
| Insufficient payload (model declined to judge) | 0.014 | 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 it