Alkylnaphthalenes and other bicyclic aromatics — production and uses

Apart from naphthalene, other commercially important bicyclic aromatics are especially biphenyl (also referred to as diphenyl), acenaphthene and acenaphthylene. Like the methylnaphthalenes, they are present in varying concentrations in coal tar. Where the concentration is sufficiently high, as is the case for methylnaphthalenes and acenaphthene (or acenaphthylene), then they are recovered from coal tar; for compounds present in low concentrations, on the other hand, such as biphenyl, production is normally via a synthetic route.