#perfluorinated

Another snapshot from fluorous chemistry. Under the organic layer that small yellow oily layer is a highly fluorous.

Fluorous chemistry involves the use of perfluorinated compounds or perfluorinated substituents to facilitate recovery of a catalyst or reaction product. Perfluorinated groups impart unique physical properties including high solubility in perfluorinated solvents. 

A perfluorinated compound (PFC) is an organofluorine compound containing only carbon-fluorine bonds (no C-H bonds) and C-C bonds but also other heteroatoms. PFCs have properties that represent a blend of fluorocarbons (containing only C-F and C-C bonds) and the parent functionalized organic species. For example, perfluorooctanoic acid functions as a carboxylic acid but with strongly altered surfactant and hydrophobic characteristics.