benzene have been propo d CHAPTER 15 Benzene and Aromaticity Electrophilic Aromatic Substitution The ee ular structure of benzene is: 架 15-1 Naming the Benzenes 图 e is considered the "pa tic molecule. 上agmw 6-d ted benzenes are named using the prefixes en的ateeezenesaeohennamedbyaddngaprefix化 点 1 1 CHAPTER 15 Benzene and Aromaticity: Electrophilic Aromatic Substitution Benzene has the empirical formula CH. Its molecular formula has been shown to be C6H6, which implies four degrees of unsaturation in the molecule. Several incorrect structures of benzene have been proposed in the past: Of these, only Claus benzene has not been synthesized. All of the other structures represent unstable substances which isomerize to benzene in very exothermic reactions. The correct molecular structure of benzene is: Benzene is relatively inert. Among the reactions it does undergo is the reaction with bromine in the presence of catalytic amounts of FeBr3: The addition product is not formed, as might be expected. Further reaction with bromine leads to a mixture of isomeric di-substituted products: 15-1 Naming the Benzenes Benzene and its derivatives were originally called “aromatic compounds” because of their strong aromas. Benzene is considered the “parent” aromatic molecule. The structure of benzene is written as a pair of resonance structures or as a regular hexagon containing an inscribed circle: Monosubstituted benzenes are often named by adding a prefix to the word benzene: Disubstituted benzenes are named using the prefixes: •1,2- (ortho-, or o-) •1,3- (meta-, or m-) •1,4- (para-, or p-) The substituents are then listed in alphabetical order: