(芳香化合物的亲电取代教学课件

Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,*,*,单击此处编辑母版标题样式,*,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,(芳香化合物的亲电取代,(芳香化合物的亲电取代(芳香化合物的亲电取代Chapter 8 Electrophilic Aromatic Substitution,(芳香化合物的亲电取代,Ar-H=aromatic compound,1.Nitration,Ar-H +HNO3,H2SO4 Ar-NO2 +H2O,Sulfonation,Ar-H +H2SO4,SO3 Ar-SO3H +H2O,Halogenation,Ar-H +X2,Fe Ar-X +HX,Friedel-Crafts alkylation,Ar-H +R-X,AlCl3 Ar-R +HXFriedel-Crafts alkylation(variations),Ar-H +R-X,AlCl3 Ar-R +HX,Ar-H +R-OH,H+Ar-R +H2O,c)Ar-H +Alkene,H+Ar-R,nitrobenzene,slower,than the same reactions with benzene,Substituent groups on a benzene ring affect electrophilic aromatic substitution reactions in two ways:,reactivity,activate (faster than benzene),or deactivate(slower than benzene),orientation,ortho,-,+,para,-,direction,or,meta-,direction,-CH,3,activates the benzene ring towards EAS,directs substitution to the,ortho-,&,para-,positions,-NO,2,deactivates the benzene ring towards EAS,directs substitution to the,meta,-position,Common substituent groups and their effect on EAS:,-NH,2,-NHR,-NR,2,-OH,-OR,-NHCOCH,3,-C,6,H,5,-R,-H,-X,-CHO,-COR,-SO,3,H,-COOH,-COOR,-CN,-NR,3,+,-NO,2,increasing reactivity,ortho/para,directors,meta,directors,If there is more than one group on the benzene ring:,The group that is more activating(higher on“the list”)will direct the next substitution.,You will get little or no substitution between groups that are,meta,-to each other.,Orientation and synthesis,.,Order is important!,synthesis of,m,-bromonitrobenzene from benzene:,synthesis of,p,-bromonitrobenzene from benzene:,You may assume that you can separate a pure,para-,isomer from an,ortho-,/,para-,mixture.,note:the assumption that you can separate a pure para isomer from an ortho/para mixture does not apply to any other mixtures.,synthesis of benzoic acids by oxidation of CH,3,Links to problem sets on the web involving EAS:,chemistry2.csudh.edu/organic/aromatics/reactions.html,Reactivity and sites on monosubstituted benzene,Reaction Sties on disubstituted benzenes,Synthesis of disubstituted benzenes,Synthesis of trisubstituited benzenes,+,HO-NO,2,+H,2,SO,4,H,2,O-NO,2,+HSO,4,-,+,+,H,2,O-NO,2,H,2,O +NO,2,H,2,SO,4,+H,2,O HSO,4,-,+H,3,O,+,HNO,3,+2 H,2,SO,4,H,3,O,+,+2 HSO,4,-,+NO,2,+,nitration,nitration:,electrophile,resonance,Mechanism for nitration:,Mechanism for sulfonation:,Mechanism for halogenation,:,Mechanism for Friedel-Crafts alkylation,:,Mechanism for Friedel-Crafts with an alcohol&acid,Mechanism for Friedel-Crafts with alkene&acid:,electrophile in Friedel-Crafts alkylation=carbocation,“Generic”Electrophilic Aromatic Substitution mechanism:,Why,do substituent groups on a benzene ring affect the reactivity and orientation in the way they do?,electronic effects,“pushing”or“pulling”electrons by the substituent.,Electrons can be donated(“pushed”)or withdrawn(“pulled”)by atoms or groups of atoms via:,Induction,due to differences in electronegativities,Resonance,delocalization via resonance,X,Common substituent groups and their effect on,reactivity,in EAS:,-NH,2,-NHR,-NR,2,-OH,-OR,-NHCOCH,3,electron donating,-C,6,H,5,-R,-H,-X,-CHO,-COR,-SO,3,H,-COOH,-COOR electron withdrawing,-CN,-NR,3,+,-NO,2,increasing reactivity,Electron donating groups activate the benzene ring to electrophilic aromatic substitution.,electron donating groups increase the electron density in the ring and make it more reactive with,electrophiles,.,electron donation stabilizes the intermediate,carbocation,lowers the,Eact,and increases the rate.,Electron withdrawing groups deactivate the benzene ring to electrophilic aromatic substitution.,electron withdrawing groups decrease the electron density in the ring and make it less reactive with,electrophiles,.,electron withdrawal destabilizes the intermediate,carbocation,raising the,Eact,and slowing the rate.,If G is an electron,donating group,these structures are especially,stable,.,Electron,donating,groups,stabilize,the intermediate carbocations for,ortho-,and,para-,in EAS more than for,meta-,.The Eacts for,ortho-/para-,are lower and the rates are faster.,Electron,donating,groups direct,ortho-/para-,in EAS,If G is an electron,withdrawing,group,these structures are especially,unstable,.,Electron,withdrawing,groups,destabilize,the intermediate carbocations for,ortho-,and,para-,in EAS more than for,meta-,.,The Eacts for,ortho-/para-,are higher and the rates are slower.,Electron,withdrawing,groups direct,meta-,in EAS,Halogens are electron withdrawing but are ortho/para directing in EAS.,The halogen atom is unusual in that it is highly electronegative but also has unshared pairs of electrons that can be resonance donated to the carbocation.,Common substituent groups and their effect on EAS:,-NH,2,-NHR,-NR,2,-OH,-OR,-NHCOCH,3,-C,6,H,5,-R,-H,-X,-CHO,-COR,-SO,3,H,-COOH,-COOR,-CN,-NR,3,+,-NO,2,increasing reactivity,ortho/para,directors,meta,directors,谢谢！,61,、奢侈是舒适的，否则就不是奢侈。,CocoChanel,62