Nomenclature of Naming Aromatic Hydrocarbons

Nomenclature of Aromatic Compounds Aromatic Compounds- possess a ring shaped structure Benzene (C6H6)- aka. naphtha - unsaturated cyclic compound - simplest aromatic HC - all C to C bonds are identical; each C has a H atom - substitution reactions occur instead of addition reaction - delocalized pi bonding in benzene imparts stability (aromaticity); responsible for resistance to addition reactions (involve breaking delocalized bonding) Benzene Derivatives- produced when one or more H atoms on benzene is/ are replaced by new group/s such as alkyl groups (methyl, ethyl and so on) or halogens. Common groups include hydroxyl (- OH), amino ( -NH2), nitro (-NO2), and carboxyl (-COOH) Naming Benzene Derivatives using IUPAC System Monosubstituted benzene: name of substituent + benzene F F NO2 Nitrobenzene CH2CH3 Ethylbenzene Note 1: A few monosubstituted benzenes have names wherein the substituent and the benzene ring taken together constitute a new parent name. Four important examples are: CH3 OH NH2 COOH F F F Fluorobenzene * Because all H atoms in benzene are equivalent it doesn’t matter at which vertex of the ring the substituted group is located. F

Toluene Phenol Aniline Benzoic Acid (not methyl benzene, hydroxybezene, aminobenzene, carboxyl benzene)

Examples: CH3 HO Cl 2- Chlorotoluene F 3- Fluorophenol

Note 2: For monosubstituted benzene rings that have a group attached that is not easily named as a substituent, the benzene ring is often treated as a group to this substituent. The benzene ring attachment is called a phenyl group. The compound is named according to the rules for naming alkanes, alkenes and alkynes. Trivia: Phenyl comes from “phene”, a European term used during the 1800’s for benzene.

Example:

CH2 = CH – CH – CH3

3- Phenyl-1-butene

Substituted benzene: position and name substituent/s (alphabetical) + benzene Note 1: When substituents are two or more, they must be given lowest possible no. and use prefixes di-, tri-, and so on if