Aromatic hydrocarbon compounds are hydrocarbons containing one or more aromatic rings, such as the single-ring benzene as well as the multiring systems: naphthalene, anthracene, and phenanthrene ring systems, which may be linked up with (substituted) naphthene rings and/or paraffinic side chains.
Aliphatic solvents are in the category of aliphatic compounds. Aliphatic solvents do not contain a benzene ring. They are mixtures of saturated, long straight chain (normal-paraffin), branched chain (iso-paraffin) or cyclic paraffins. These solvents are produced by the distillation of crude oil by the appropriate boiling point range fraction, and then are treated to improve their color and odor.
An intermediate or reaction intermediate is a substance formed during a middle step of a chemical reaction between reactants and the desired product. Intermediates tend to be extremely reactive and short-lived, so they represent a low concentration in a chemical reaction compared with the amount of reactants or products. Many intermediates are unstable ions or free radicals.