Sec 1 Structure and Stability 146pm 140pm 140pm 140pm 微微米 pm 134pm 140pm 140pm AdGif-UNREGISTERED 芳香性
Sec 1 Structure and Stability 芳香性 140 pm 140 pm 140 pm 140 pm 140 pm 140 pm 146 pm 134 pm 微微米
Unusual Reactions -Alkene KMnO>diol (addition) ■Benzene+KMnO4-→no reaction. -Alkene Br2/CCl4>dibromide (addition) Benzene Br2/CCl4->no reaction. -With FeCla catalyst,Br2 reacts with benzene to form bromobenzene HBr(substitution!) Double bonds remain
Unusual Reactions ▪Alkene + KMnO4 → diol (addition) ▪ Benzene + KMnO4 → no reaction. ▪Alkene + Br2 /CCl4 → dibromide (addition) ▪ Benzene + Br2 /CCl4 → no reaction. ▪With FeCl3 catalyst, Br2 reacts with benzene to form bromobenzene + HBr (substitution!). ▪ Double bonds remain
Sec 1 Structure and Stability -Unusual Stability Hydrogenation of just one double bond in benzene is endothermic! Benzene is 150 kJ/mol(36 kcal/mol)more stable than might be expected for "cyclohexatriene" (-359 predicted) 151kJ (-240 predicted) resonance energy energy 8kJ resonance energy -240 kJ/mol -232 kJ/mol -208 kJ/mol -120 kJ/mol energy
Sec 1 Structure and Stability ▪Unusual Stability ▪ Hydrogenation of just one double bond in benzene is endothermic! ▪ Benzene is 150 kJ/mol (36 kcal/mol) more stable than might be expected for “cyclohexatriene
Sec 1 Structure and Stability Benzene -Benzene is unsaturated ■ Benzene is much less reactive than typical alkene and fails to undergo the usual alkene reactions Cyclohexene reacts rapidly with Br2 and gives the addition product 1,2-dibromocyclohexane Benzene reacts only slowly with Br2 and gives the substitution product C6HsBr Fe Br2 catalyst +HBr B Benzene Bromobenzene (Addition product) (substitution product) not formed
Benzene ▪ Benzene is unsaturated ▪ Benzene is much less reactive than typical alkene and fails to undergo the usual alkene reactions ▪ Cyclohexene reacts rapidly with Br2 and gives the addition product 1,2-dibromocyclohexane ▪ Benzene reacts only slowly with Br2 and gives the substitution product C6H5Br Sec 1 Structure and Stability
Physical Properties Physical Properties of benzene 1.It is a colourless liquid with boiling point 80C. 2. It is insoluble in water but soluble in organic solvent. 3. It burns with a sooty flame and it is highly inflammable. 4.It is carcinogenic.致癌物（质）的
Physical Properties Physical Properties of benzene 1. It is a colourless liquid with boiling point 80oC. 2. It is insoluble in water but soluble in organic solvent. 3. It burns with a sooty flame and it is highly inflammable. 4. It is carcinogenic.致癌物(质)的