2 Aromatic Compounds Unsaturated hydrocarbons Some of them have pleasant odors.Aromatic compounds
3 Aromatic Compounds Aromatic compounds contain benzene ring. Benzene has:6 C atoms and 6 H atoms.Two possible Lewis structures.C6H6
4 Aromatic CompoundsArene: A compound containing one or more benzene rings.Aryl group: When we remove a H atom from an arene (Ar-).Phenyl C6H5-
5 Naming of Aromatic Compounds Aromatic compounds are named:With benzene as the parent chain.Name of substituent comes in front of the “benzene”.methylbenzene chlorobenzene ethylbenzeneCH3ClCH2-CH3
6 Naming of Aromatic Compounds Some substituted benzenes have common names.CH3Toluene
7 Naming of Aromatic Compounds When two groups are attached to benzene, the ring is numbered to givethe 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-methyltolueneOrthoMetaPara
8 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.
9 Naming of Aromatic Compounds Aryl group: When we remove a H atom from an arene (Ar-).Phenyl C6H5-1
10 Chemical properties of benzene Resonance: stableResonance hybrid: a molecule with two or more Lowis structures.Contributing structure
11 Chemical properties of benzene No addition reactions (almost unreactive)Aromatic substitution: One of the H atoms is repalecd by some groups.HalogenationNitrationSulfonation
12 Chemical properties of benzene 1. Halogenation:Cl and Br react rapidly with benzene in the presence of an iron catalyst.
13 Chemical properties of benzene 2. Nitration:In presence of concentrated nitric acid and sulfuric acid,one of the H atoms is replaced by a nitro (-NO2) group.
14 Chemical properties of benzene 3. Sulfonation:In presence of concentrated sulfuric acid and heat,one of the H atoms is replaced by sufonic acid (-SO3H) group.Heat
15 Phenol OH Phenol is the IUPAC name for benzene with a hydroxyl group. 1123Cl33-Chloro-2-nitrophenol(m-Cresol)
16 Phenol Many are used as antiseptics and disinfectants. Phenols are found widely in nature.Phenols are weak acids (pKa~10).Phenols are insoluble in water.
17 Phenols as antioxidants Autoxidation: foods and other materials that contain C=C are oxidized only in presence of oxygen (no other reactant).R-H group is converted to an R-O-O-H (hydroperoxide)group.
18 Phenols as antioxidants Phenols are antioxidants and can prevent autoxidation.Vitamin E is a natural antioxidant.The foods are stored in longer period.