CBSE Class 11-science Answered

The aromatic - residue is called phenyl. The name depends on the length of the alkyl substituent. If the substituent contains no more than six carbon atoms, the compound's parent name is benzene. This would then be classified as an alkylbenzene, such as is the case with ethylbenzene and 2-pentylbenzene. However, if the alkyl substituent possesses more than six carbon atoms, the compound is considered to be a phenylalkane (or -alkene, or -alkyne, respectively), such is the case with 3-phenyloctane. Above all in empirical and structural formulas, the phenyl group is often abbreviated by "Ph". The namephenyl derives from the Greek word "phainein" (= shine), as Michael Faraday first discovered phenol in the liquid residue that condensed from the gas phase in London's street lamps when whale oil was burnt. The - residue is calledbenzyl.

The relative position of substituents in double-substituted benzenes is indicated by the prefixes ortho (o), meta (m) and para (p). The substituent's relative position in ortho-substituted benzenes is "1,2". It is "1,3" in meta-substituted benzenes and "1,4" in para-substituted benzenes. The prefixes ortho, meta, and para, or their abbreviations o, m, and p, respectively, are written in italics when used with compound names.