有機化學第16ç« ï&f

有機化學第16ç« ï&f

Info iconThis preview shows pages 1–11. Sign up to view the full content.

View Full Document Right Arrow Icon
2009/3/17 1 16. Chemistry of Benzene: Electrophilic Aromatic Substitution 親電子芳香取代反應 Benzene is aromatic: a cyclic conjugated compound with 6 π electrons Reactions of benzene lead to the retention of the aromatic core Electrophilic aromatic substitution replaces a proton on benzene with another electrophile 醯化 鹵化 硝化 磺酸化 烷化
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2009/3/17 2 Why this Chapter? Understand reactions Examine relationship Between aromatic structure and reactivity 3 p. 561 OUTLINE ± Bromination of Aromatic Rings 溴化 Bromination of Aromatic Rings ± Other Aromatic Substitution 其他 ± Alkylation of Aromatic Rings 烷化 The Friedel-Crafts Reaction ± Acylation of Aromatic Rings 醯化
Background image of page 2
2009/3/17 3 OUTLINE ± Substitution Effect in Substituted Aromatic Rings ± An Explanation of Substituent Effects ± Trisubstituted Benzenes OUTLINE ± Nucleophilic Aromatic Substitution ± Benzyne 苯炔 ± Oxidation of Aromatic Compounds ± Reduction of Aromatic Compounds ± Synthesis of Trisubstituted Benzenes
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2009/3/17 4 16.1 Electrophilic Aromatic Substitution Reactions: Bromination Benzene’s π electrons participate as a Lewis base in reactions with Lewis acids 7 The product is formed by loss of a proton, which is replaced by bromine Addition Intermediate in Bromination In the first step the π electrons act as a nucleophile toward Br 2 (in a complex with FeBr 3 ) The intermediate is not aromatic and therefore high in energy This forms a cationic addition intermediate from benzene and a bromine cation 8 The benzene reaction is slower because the starting material is more stable
Background image of page 4
2009/3/17 5 Formation of Product from Intermediate The cationic addition intermediate transfers a proton to FeBr 4 - (from Br - and FeBr 3 ) 9 This restores aromaticity (in contrast with addition in alkenes) Addition & Substitution 10
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2009/3/17 6 P. 16.1 11 P. 16.1 12
Background image of page 6
2009/3/17 7 The reaction with bromine involves a mechanism that is similar to many other 16.2 Other Aromatic Substitutions mechanism that is similar to many other reactions of benzene with electrophiles 13 Aromatic Chlorination 氯化 Chlorine and iodine (but not fluorine, which is too reactive) can produce aromatic substitution with the addition of other reagents to promote the reaction Chlorination requires FeCl 3 抗焦慮症 14
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2009/3/17 8 Aromatic Iodination 碘化 Iodine must be oxidized to form a more powerful + species a more powerful I species (with Cu + or peroxide) 15 甲狀腺荷爾蒙的製備 p. 551 16
Background image of page 8
2009/3/17 9 Aromatic Nitration The combination of nitric acid and sulfuric acid produces NO 2 + (nitronium ion) The reaction ith ben ene prod ces nitroben ene 硝化 The reaction with benzene produces nitrobenzene 17 From nitrobenzene to PU Methylene diphenyl diisocyanate , most often abbreviated as MDI 18
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2009/3/17 10 Six steps to prepare 4,4'-MDI ± Nitration: Reaction of benzene with nitric acid and a catalyst, to form nitrobenzene ± Hydrogenation: Reaction of the nitrobenzene with hydrogen and a catalyst, to form aniline ± Aniline/Formaldehyde condensation: Reaction of the aniline with formaldehyde
Background image of page 10
Image of page 11
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 64

有機化學第16ç« ï&f

This preview shows document pages 1 - 11. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online