Scalable and Concise Approaches for the Synthesis of "Archipelago Model" Asphaltene Compounds
Bibliographic record
Abstract
Asphaltenes constitute the most difficult sub-class of bitumen with regards to upgradability. This is due to their complex and variable structure, higher average molecular weight, and inclusion of polar functionalities. These structural traits instigate intermolecular attractions that lead to irreversible aggregation of individual asphaltene molecules and ultimately precipitation from solution. This behavior hampers the ability to efficiently utilize this material and address society’s growing energy needs. At the same time, northern Alberta’s Athabasca region has abundant reserves of asphaltene-rich bitumen. There is thus strong interest in developing new technologies for efficient upgrading of this “low quality” crude petroleum. Progress towards this end requires a thorough understanding of asphaltenes at a molecular and supramolecular level. Due to the complex and intractable mixture that comprises asphaltenes, this intimate knowledge has yet to be garnered, despite great effort. Traditionally, an analytical approach towards deciphering the “micro-structure” of the asphaltenes has been utilized, with limited results that are difficult or impossible to validate. As of yet, no pure asphaltene molecule has been characterized structurally. A reverse-engineering approach towards accurate modeling of theoretical class members is expected to have great potential in unraveling the mysteries that remain. In this dissertation is described the first concise and scalable synthesis of a range of well-defined asphaltene model compounds obtained in high purity. This new class of synthetic compounds falls within the observed structural guidelines determined for natural samples, both in terms of molecular weight and heteroatom content. These model compounds represent the “archipelago-type” architecture, in that they are composed of polycyclic aromatic “islands” tethered together by saturated alkyl chains of various lengths, and further decorated with shorter terminal alkyl groups. A range of authentic functionality has been introduced into these compounds, although there remain many variants as yet unprepared. The foundation of our synthetic approach to these molecules is the traceless cross-coupling of tethers and islands, assembling large carbonaceous skeletons in the terminal step of the synthetic sequence. This feature is pivotal in allowing for simple isolations of otherwise difficult-to-purify targets through extraction and fractional crystallization. All of the reported archipelago model compounds and isolated intermediates have been characterized by 1H- and 13C-NMR spectroscopy, HRMS, and EA. The solid-state structure of one model compound has been determined by X-ray crystallography.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.002 |
| Insufficient payload (model declined to judge) | 0.004 | 0.002 |
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".