1) Aromatic hydrocarbon 
Terphenyls are a group of closely related aromatic hydrocarbons. Also known as diphenylbenzenes or triphenyls, they consist of a central benzene ring substituted with two phenyl groups. The three isomers are ortho-terphenyl, meta-terphenyl, and para-terphenyl. Commercial grade terphenyl is generally a mixture of the three isomers. This mixture is ...