 Although Ph and phenyl uniquely denote C6H5, substituted derivatives also are described using the phenyl terminology.For example, O2NC6H4 is nitrophenyl and F5C6 is pentafluorophenyl.Monosubstituted phenyl groups (that is, disubstituted benzenes) are associated with electrophilic aromatic substitution reactions and the products follow the arene substitution pattern.