Tài liệu Bài giảng organic chemistry chapter8

ORGANIC CHEMISTRY Dr Nam T. S. Phan Faculty of Chemical Engineering HCMC University of Technology Office: room 211, B2 Building Phone: 38647256 ext. 5681 Email: [email protected] 1 Chapter 8: ARENES Benzene 2 CRITERIA FOR AROMATICITY To be classified as aromatic, a compound must meet both of the following criteria: • It must have an un-interrupted cyclic π cloud above & below the plane of the molecule • The π cloud must contain (4n + 2) π electrons (n = 0, 1, 2…) un-interrupted cyclic π cloud 6πe=4x1+2 3 Aromatic: (+) (-) (+) N H O S 4 NOT (4n + 2) π e NOT aromatic: (.) (+) 4πe (-) (.) 5πe 7πe 8πe Interrupted cyclic π cloud 5 NOMENCLATURE OF MONOSUBSTITUTED BENZENES Name of substituent + benzene 6 Names have to be memorized: 7 NOMENCLATURE OF DI- & POLYSUBSTITUTED BENZENES Alphabetical order, 1-position for the 1st stated substituent 8 1 of the substituents can be incorporated into a name: Names incorporating 2 substituents 9 Alphabetical order Lowest possible numbers 10 PREPARATION OF BENZENE Petroleum Bezene 11 REACTIONS OF BENZENE Halogenations of benzene 12 Reaction mechanism: electrophilic substitution Catalyst regeneration 13 Nitration of benzene 14 Sulfonation of benzene Reversible reaction 15 Reaction mechanism: electrophilic substitution 16 Friedel-Crafts Alkylations of benzene 17 18 Carbocation rearrangement 19 20