Water Enhances the Aggregation of Model Asphaltenes in Solution via Hydrogen Bonding
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Bibliographic record
Abstract
The self-association properties of two 2,2′-bipyridine derivatives, 4,4′-bis(2-pyren-1-yl-ethyl)-2,2′-bipyridine (PBP) and 4,4′-bis[2-(9-anthryl)ethyl]-2,2′-bipyridine (ABA), in water-saturated solvents were studied as models for petroleum asphaltenes. 1 H NMR spectroscopy titration experiments in chloroform established that both compounds self-associate in solution. The addition of water (ranging from 0.43 to 0.86 g/L) increased the thermal stability and the aggregation behavior of PBP and ABA at low concentration (3.06 × 10 −4 and 1.28 × 10 −3 M, respectively). The chemical shift, line-width, and spin−spin ( T 2 ) relaxation time of water protons in these solutions showed that the O−H···N hydrogen bonds between the pyridyl nitrogens of PBP/ABA and water were responsible for their aggregation at low concentration, although FTIR spectroscopy suggested that the H-bond between PBP and water was relatively weak. The solubility of water in PBP solutions showed that the number of water molecules per PBP molecule varied between 1 and 2 in water-saturated CHCl 3 and that the Gibbs free energy for the exchange of water between the aqueous phase and the solution of PBP was −16 kJ/mol at 22 °C. Water likely enhanced the stability of aggregates by reinforcing π−π interactions via water-bridged intermolecular H-bonding between the pyridyl nitrogen.
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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) | 0.000 | 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 it