The overriding chemical principles that define asphaltenes

Asphaltenes are defined in terms of their solubility classification. This o perational definition combined with the previous controversy over asphalten e molecular weight have obscured the governing chemical and structural para meters that define the asphaltene fraction. Here, asphaltenes are investiga ted by several techniques to elucidate relations between structure and prop erties. In particular, the asphaltene molecular size is compared to the rat io of aromatic to saturated carbon. The conclusion is obtained that asphalt ene molecular structure is governed by the balance between the propensity o f fused aromatic ring systems to stack via pi -bonding, reducing solubility , vs the steric disruption of stacking due alkane groups, increasing solubi lity.