1、Structure and Stability of BenzeneChemical Properties of Polycyclic Aromatic HydrocarbonsIsomerism and Nomenclature of Aromatic Hydrocarbons Aromaticity and the Huckel RuleChemical Properties of Monocyclic Aromatic HydrocarbonsChapter Six: Aromatic Hydrocarbons and AromaticityIsomerism and Nomenclat

2、ure of Aromatic Hydrocarbons1. Constitutional Isomerism of Aromatic Hydrocarbons:CnH2n-6CH2CH2CH3H3CCHCH3a. Side chain isomerism:b. Position isomerism of the substituents:2. Nomenclature of Aromatic Hydrocarbons:Isomerism and Nomenclature of Aromatic Hydrocarbonsa. Monosubstituted benzenes: are name

3、d in the same manner as other hydrocarbons, with benzene as the parent name.CH2CH2CH3H3CCHCH3PropylbenzeneIsopropylbenzene If the alkyl substituent has more than six carbons, or has carbon-carbon double bond and triple bond, the compound is named as a phenyl-substituted( (苯基取代的苯基取代的) ) alkane, alken

4、e or alkyne. For example:Isomerism and Nomenclature of Aromatic HydrocarbonsCHCH2CH2CH2CH2CH3CH32-PhenylheptaneCHCH2CHCH3CHCH35-Phenyl-2-hexeneIsomerism and Nomenclature of Aromatic Hydrocarbonsb. Disubstituted benzenes are named using one of the prefixes ortho (o, 鄰位鄰位), meta (m, 間間位位), or para (p,

5、 對位對位).CH3CH3CH3CH3CH3CH3ortho-Xylenemeta-Xylenepara-XyleneXylene-二甲苯二甲苯Isomerism and Nomenclature of Aromatic HydrocarbonsExercise： CH2CCHCH2CHCH2CH3HCH3(cis) - 5-Methyl-1-phenyl-2-hepteneStructure and Stability of BenzeneChemical Properties of Polycyclic Aromatic HydrocarbonsIsomerism and Nomencla

6、ture of Aromatic Hydrocarbons Aromaticity and the Huckel RuleChemical Properties of Monocyclic Aromatic HydrocarbonsChapter Six: Aromatic Hydrocarbons and AromaticityStructure and Stability of Benzene In 1834 the German chemist Eilhardt Mitscherlich (University of Berlin) firstly synthesized benzene

7、C6H5COOH+CaOHeatC6H6+CaCO3BenzeneBenzoic acidcalcium oxideC6H6: C:H = 1:1 In 1865, Kekule suggested that the carbon atoms of benzene are in a ring, that they are bonded to each other by alternating single and double bonds, and that one hydrogen atom is attached to each carbon atom.cyclohexatrieneStr

8、ucture and Stability of BenzeneBut:+ Br2FecatalystBr+HBrbromobenzene 溴溴苯苯BrBrHHaddition productNot found1) :2) : All its carbon-carbon bonds have the same length139 pm, intermediate between typical single (154 pm) and double (134 pm)bonds.-CyclohexaneCyclohexeneBenzeneCyclohexadiene1,3-118kJ/mol-230

9、kJ/mol-356kJ/mol-206kJ/mol(expected)(actual) 150kJ/mol(actual)(difference)Structure and Stability of Benzene3) The unusual stability We can get a quantitative idea of benzenes stability from the heats of hydrogenation.Benzene has 150kJ / mol “extra” stabilityStructure and Stability of BenzeneThe tru

10、e structure of benzene:Six electrons are completely delocalized around the ring.Structure and Stability of BenzeneChemical Properties of Polycyclic Aromatic HydrocarbonsChapter Two Saturated Hydrocarbons: Alkanes and CycloalkanesIsomerism and Nomenclature of Aromatic Hydrocarbons Aromaticity and the

11、 Huckel RuleChemical Properties of Monocyclic Aromatic HydrocarbonsChemical Properties of Monocyclic Aromatic HydrocarbonsAddition productElectrophile : E+Y-+HE+E+EY+HYEYYSbustitution productThe most common reaction of aromatic compound is electrophilic substitution(親電取代親電取代).1. Electrophilic Aromat

12、ic SubstitutionHXSO3HCORNO2RChemical Properties of Monocyclic Aromatic Hydrocarbons Many different substituents can be introduced onto the aromatic ring by electrophilic substitution reactions.halogenatesulfonatenitratealkylateacylateChemical Properties of Monocyclic Aromatic Hydrocarbons(1) Halogenation (鹵代鹵代)FeCI3CI+ CI2+ HCIFeBr3Br+ Br2+ HBrThe reactivity of halogens : F2 Cl2 Br2 I2BrBrFeBr3BrBrFeBr3+-polar