A predictive model for the aggregation of polycyclic aromatic compounds

The physical aggregation of polycyclic aromatic compounds (PACs) is a key step in soot inception. In this work, we set out to elucidate which molecular properties influence the physical growth process and use machine learning to quantitatively relate these features to the propensity of these molecules to physically dimerize with other PACs. To this end, we first develop a dataset of PAC monomers along with their calculated free energies of dimerization emphasizing a set of PACs with a diverse range of properties. First, we augment existing calculations of dimerization energies with our own molecular dynamics simulations enhanced by well-tempered Metadyanmics. We then demonstrate that a machine learning model based on the least absolute shrinkage and selection operator (Lasso) is able to quantitatively learn how molecular features contribute to physical aggregation and predict the free energy of dimerization for new pairs of molecules. The model is able to accurately determine the stability for both homodimerization and heterodimerization cases. Our approach also provides a data driven method to determine the molecular features most important to predicting the dimer stability. From this, we determine that the PAC properties most influential to physical dimerization are size, shape, oxygenation, and presence of rotatable bonds. This work highlights the molecular complexity of the PAC monomers that must be accounted for in order to accurately represent physical aggregation. We anticipate that this approach will allow for more effective modeling of the PAC dimerization process as it facilitates the efficient prediction of dimerization propensity from easily calculable molecular features.

Rediscovering the Bacon’s Hydrazine/Phenylhydrazine Mediated Cyclization of 2,2’-Dicarbonylbi(hetero)aryls: Construction of (5-Azo)-/Indazolo[2,3-a]quinolines

The hydrazine/phenylhydrazine mediated reductive dicarbonyl coupling reactions have been carried out under mild condition to arrive the construction of polycyclic aromatic compounds and azo-substituted polyaromatic compounds having a broad substrate...

Bituminous substances in soils of Baikal Rift zone

Parameters of hydrocarbon complex of the soils of lacustrine-alluvial plain and sandy uplands of the Baikal rift zone within the Barguzin Depression have been studied. Data were obtained on organic (non-carbonate) carbon, chloroform and hexane bitumoids, as well as on individual polycyclic aromatic hydrocarbons. The content, composition and properties of bitumoids vary depending on the intensity of endogenous activity. In soils located in the zone of active unload of hydrothermal waters and hydrocarbon fluids, atypical accumulation of organic carbon was noted; the concentrations of bitumoids do not correlate with its content. High values of the bitumoid coefficient, significant level of polycyclic aromatic compounds and their diversity, in combination with salts accumulation, indicate an additional influx of hydrocarbons and instability of the soil hydrocarbon system. The level of the indicators shifts towards background values in the soils of sandy hills with a complex combination of exogenous and endogenous factors of soil forming. Studied parameters of the soil hydrocarbon system in aggregate can serve as markers of the intensity of endogenous processes.