Chapter 14: Aromatic CompoundsLearning Objectives:1. Recognize and distinguish between aromatic and antiaromatic compounds by their structures.2. Know the properties of aromatic and antiaromatic compounds, and the chemical consequences of aromaticity.3. Recognize and be able to write the mechanism of electrophilic aromatic substitution4. Be able to outline the completed electrophilic aromatic substitution reactions of the following types: halogenation, nitration, sulfonation, and Friedel-Crafts acylation & alkylationSections:14.1 Armoatic Compounds Are Unusually Stable14.2 The Two Criteria for Aromaticity*14.3 Applying the Criteria for Aromaticity14.4 Aromatic Heterocyclic Compounds14.5 Some Chemical Consequences of Aromaticity*14.6 Antiaromaticity14.7 A Molecular Orbital Description of Aromaticity and Antiaromaticity14.8 Nomenclature of Monosubstituted Benzenes14.9 How Benzene Reacts*14.10 The General Mechanism for Electrophilic Aromatic Substitution Reactions*14.11 Halogenation of Benzene*14.12 Nitration of Benzene*14.13 Sulfonation of Benzene*14.14 Friedel-Crafts Acylation of Benzene*14.15 Friedel-Crafts Alkylation of Benzene*14.16 Alkylation of Benzene by Acylation-Reduction*14.17 Using Coupling Reaction to Alkylate Benzene#14.18 It Is Important to Have More Than One Way to Carry Out a Reaction14.19 How Some Substituents Can Be Chemically Changed** Sections that will be focused# Sections that will be skippedRecommended additional problems14.30 – 14.491Class Note14.1 Armoatic Compounds Are Unusually StableH2NiH = -28.6 kcal/molEnergy-28.6 kcal/molcyclohexatriene(hypothetical)-85.8 kcal/mol(-28.6x3)+ H2+ 3H2+ 3H2-49.8 kcal/mol36 kcal/mol214.2 The Two Criteria for Aromaticity* and 14.6 AntiaromaticityA. Cyclic moleculeB. Every atom has p orbitalC. Planar moleculeD. Comply with 4n+2 rule (as compared with 4n rule)E. Consequence of aromaticity314.3 Applying the Criteria for Aromaticity and 14.4 Aromatic Heterocyclic Compounds4HNHNNHN O SNO SNNNHHNOHCH3CH2CH2NNNHNOOOHOH514.5 Some Chemical Consequences of Aromaticity*A. Acidity of protonsHHH HB. Aromaticity on leaving groupBrBr6C. Aromaticity on dipole moment (polarity)OO714.7 A Molecular Orbital Description of Aromaticity and Antiaromaticity814.8 Nomenclature of Monosubstituted BenzenesClBrNO2CH3OHNH2SO3HOCH3CHOCO2HCHCH3CH3As substituent:CH2914.9 How Benzene Reacts* and 14.10 The General Mechanism for Electrophilic Aromatic Substitution Reactions*Addition vs. SubstitutionElectrophilic Aromatic Substitution vs. Nucleophilic Aromatic Substitution10A. General Mechanism of Electrophilic Aromatic SubstitutionB. Reaction coordinate diagram1114.11 Halogenation of Benzene*14.12 Nitration of Benzene*1214.13 Sulfonation of Benzene*14.14 Friedel-Crafts Acylation of Benzene*1314.15 Friedel-Crafts Alkylation of Benzene*Result from carbocation migration1414.16 Alkylation of Benzene by Acylation-Reduction* and 14.18 It Is Important to Have More Than One Way to Carry Out a ReactionA. Clemmensen reductionB. Wolff-Kishner reduction1514.19 How Some Substituents Can Be Chemically Changed*A. Reactions of Alkyl SubstituentsNBSperoxideor hBrOHCNtert-BuO16H2, PtNOH2, PtH2, PtB. Oxidations of Alkyl Substituents1. KMnO4, heat (reflux)2. H+Na2Cr2O7, H+, heat17Na2Cr2O7, H+, heatNa2Cr2O7, H+, heatNa2Cr2O7, H+, heatOHMnO2 (no heating needed)OHNa2Cr2O7, H+, heat18C. Reduction of Nitro GroupH2, PtNO2NO2Sn, HClNO2Fe,