1 3 Aromatic Hydrocarbons Aromatic Compounds Unsaturated hydrocarbons

1. 3 Aromatic Hydrocarbons

Aromatic Compounds Unsaturated hydrocarbons Some of them have pleasant odors. Aromatic compounds

Aromatic Compounds Aromatic compounds contain benzene ring. Benzene has: C 6 H 6 • 6 C atoms and 6 H atoms. • Two possible Lewis structures.

Aromatic Compounds Arene: A compound containing one or more benzene rings. Aryl group: When we remove a H atom from an arene (Ar-). Phenyl C 6 H 5 -

Naming of Aromatic Compounds Aromatic compounds are named: • With benzene as the parent chain. • Name of substituent comes in front of the “benzene”. CH 3 Cl methylbenzene chlorobenzene CH 2 -CH 3 ethylbenzene

Naming of Aromatic Compounds Some substituted benzenes have common names. CH 3 Toluene

Naming of Aromatic Compounds When two groups are attached to benzene, the ring is numbered to give the lower numbers to the substituents. - Start numbering from a special name (if we have). - If we do not have, number them to get the smallest set of numbers. - List them by alphabetical order. 3 -methyltoluene Ortho Meta Para

Naming of Aromatic Compounds If we have three or more substituents: - Start numbering from a special name (if we have). - If we do not have, number them to get the smallest set of numbers. - List them by alphabetical order.

Chemical properties of benzene 1. Substitution: Cl and Br react rapidly with benzene in the presence of an iron catalyst.

Phenol OH • Phenol is the IUPAC name for benzene with a hydroxyl group. Phenol 1 1 NO 2 2 3 3 Cl 3 -Chloro-2 -nitrophenol (m-Cresol)

Phenol - Many are used as antiseptics and disinfectants. - Phenols are found widely in nature. - Phenols are weak acids (p. Ka~10). - Phenols are insoluble in water.

Phenols as antioxidants Phenols are antioxidants and can prevent autoxidation. Vitamin E is a natural antioxidant. The foods are stored in longer period.