TAILIEUCHUNG - Chapter 8: ARENES

To be classified as aromatic, a compound must meet both of the following criteria: It must have an un-interrupted cyclic p cloud above & below the plane of the molecule. The p cloud must contain (4n + 2) p electrons (n = 0, 1, 2 ). | ORGANIC CHEMISTRY Dr Nam T. S. Phan Faculty of Chemical Engineering HCMC University of Technology Office: room 211, B2 Building Phone: 8647256 ext. 5681 Email: ptsnam@ Chapter 8: ARENES Benzene CRITERIA FOR AROMATICITY To be classified as aromatic, a compound must meet both of the following criteria: It must have an un-interrupted cyclic p cloud above & below the plane of the molecule The p cloud must contain (4n + 2) p electrons (n = 0, 1, 2 ) un-interrupted cyclic p cloud 6 p e = 4 x 1 + 2 Aromatic: NOT aromatic: 4 p e 5 p e 7 p e 8 p e NOT (4n + 2) p e Interrupted cyclic p cloud NOMENCLATURE OF MONOSUBSTITUTED BENZENES Name of substituent + benzene Names have to be memorized: NOMENCLATURE OF DI- & POLYSUBSTITUTED BENZENES Alphabetical order, 1-position for the 1st stated substituent 1 of the substituents can be incorporated into a name: Names incorporating 2 substituents Alphabetical order Lowest possible numbers PREPARATION OF BENZENE Petroleum Bezene REACTIONS OF BENZENE Halogenations of benzene Reaction mechanism: electrophilic substitution Catalyst regeneration Nitration of benzene Sulfonation of benzene Reversible reaction Reaction mechanism: electrophilic substitution Friedel-Crafts Alkylations of benzene Carbocation rearrangement Friedel-Crafts Acylations of benzene Reaction mechanism: electrophilic substitution Rearrangement REACTIONS OF SUBSTITUTED BENZENES Relative rates of electrophilic substitutions: Electron-donating Electron-withdrawing Relative reactivity Electron-donating Eelectron-withdrawing Activating Deactivating ortho/para-directing meta-direcring +I, +C, +H - I, -C, EFFECTS OF SUBSTITUENTS ON ORIENTATION E/D group Only for halogen group E/W group E/D group E/W group THE ORTHO-PARA RATIO Increase in the size of substituents Decrease in the o/p ratio ADDITIONAL CONSIDERATIONS More deactivating than halogen, the ring is too unreactive for (only) Friedel-Crafts alkylations & acylations Aniline & N-substituted anilines do NOT undergo Friedel-Crafts reactions: More deactivating than halogen Phenol & anisole do undergo Friedel-Crafts reactions, orienting ortho & para – oxygen does NOT complex with the Lewis acid Also can NOT undergo nitration – primary amines are easily oxidized SYNTHESIS OF TRISUBSTITUTED BENZENES More activating substituent controls the regioselectivity HALOGENATIONS OF ALKYL SUBSTITUENTS NOT Lewis acid Can undergo E1 & E2, SN1 & SN2 reactions as usual OXIDATIONS OF ALKYL SUBSTITUENTS NUCLEOPHILIC AROMATIC SUBSTITUTION REACTIONS E/W groups must be positioned ortho / para to the halogen The greater the number of E/W substituents, the easier it is to carry out the reaction

• Hoá học
• organic chemistry
• hóa hữu cơ
• công nghệ hóa học
• Chemical Engineering
• arenes
• In this workbook
• experiments are elaborated using small scale glassware and equipments from a Small Lab Kit
• developed at the Department of Chemistry
• Faculty of Science
• Chulalongkorn University in Thailand
• This Small Lab Kit was created as a result of the research project entitled “Chemistry Laboratory Based on Chemical Safety and Pollution Minimization” sponsored by Thai Research Fund (RDG 3 07 2543)
• One of the outcomes of this project is the organic laboratory book entitled “Organic Chemistry Laboratory Based on Chemical Safety and Pollution Minimization” written in Thai by professors from 7 universities in this project
• They compiled
• adjusted and tested the experiments taken from several traditional organic chemistry laboratory books using the prototype of Small Lab Kit
• Currently
• some selected experiments from this Thai organic chemistry laboratory text have further been modified
• rewritten and edited in English as appeared in this workbook
• Some experiments ar
• Ebook Organic chemistry
• Nucleophilic substitution
• Determining organic structures
• nucleophilic addition
• Organic structures
• Electrophilic aromatic substitution
• Principles of organic chemistry
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• The methane series
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• Polybasic acids
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• Hóa học hữu cơ
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• Chemistry of benzene
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• Summary of Organic Chemistry Dotoral Thesis
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