郑州大学 有机化学7芳香烃

Chapter7AromaticHydrocarbonsHydrocarbons(烃)Aliphatic~(脂肪烃)Alicyclic~(脂环烃)Aromatic~,arenes(芳香烃)Aliphatic:fattyAromatic:fragrantAnise(大茴香)cinnamon(肉桂)Thyme(麝香草)cloves(丁香)Cumin(小茴香)Aromaticity(芳香性)cyclicandfullyconjugated4n+2πelectronsinthesystemtheentiresystemisplanarspecialchemicalstabilitysubstitutionreactionsinsteadofadditionMonocyclicarenes(单环芳香烃)Biphenyls(联苯类)

Multiphenylaliphatichydrocarbons(多苯代脂肪烃)Fused-ringarenes(稠环芳香烃)Nonbenzenoidsystem(非苯体系)Heterocycliccompounds(杂环化合物)7.1Structureofbenzene(苯的结构)Kekuléstructure“Butlook!Whatwasthat?Oneofthesnakeshadseizedholdofitsowntail,andtheformwhirledmockinglybeforemyeyes.Then,asifbyaflashoflightningIawoke.”Itremainschemistry'smostfamousahamoment.“Letuslearntodream,thenperhapsweshallfindthetruth.”Kekulésuggestedthattwoisomericstructurescouldexistbutinterconvertedtoorapidlytobeseparated.Tautomerism(互变异构)Butbenzenebehavesunlikean

alkene.

sp2hybridedResonancetheoryMolecularorbitalsTherearesixbondinginteractionsinthelowest-energyMO(ψ1,theGreekletterpsi)ofbenzene.ThetwootherbondingMOsofbenzene(ψ2andψ3)aredegenerate:ψ2hasfourbondinginteractionsandtwoantibondinginteractions,foranetresultoftwobondinginteraction,andψ3alsohastwobondinginteractions.Thus,ψ2andψ3arebondingMOs,buttheyarenotasstrongasstronglyasψ1.7.2Nomenclatureofderivativesofbenzene(苯衍生物的命名)苯作为母体甲(基)苯异丙苯氯(代)苯硝基苯1,2-二甲苯1-甲基-3-乙基苯1-甲基-4-叔丁基苯邻二甲苯间甲乙苯对甲叔丁苯o-二甲苯m-甲乙苯p-甲叔丁苯1,2,3-三甲苯1,3,5-三甲苯

1,2,4-三甲苯连三甲苯均三甲苯偏三甲苯

4-甲基-2-乙基-1-丙基苯甲氧基苯乙烯基苯苯甲醚苯乙烯苯作为取代基苯基C6H5-Ph-Ф-2,3-二甲基-4-苯基己烷苯乙炔苯甲酸2-苯基丙酸

α

-苯基丙酸邻苯二甲酸酐苯胺对苯二酚间苯二胺1-苯基乙醇苯磺酸基团的重要性-COOH>-SO3H>-COOR>-COX>-CONH2>-OCOR>-CN>-CHO>-COR>-OH>-NH2>-OR>-R>-X>-NO2>-NO对硝基氯苯邻羟基苯甲酸邻乙酰氧基苯甲酸

水杨酸乙酰水杨酸(阿司匹林)苯乙酮邻乙酰基苯甲酸甲酯7.3Physicalpropertiesofbenzene(苯的物理性质)7.4Reactionsofbenzene-Electrophilicsubstitution(亲电取代)Reactionofsimplealkeneswithelectrophiles:

Underthesameconditions,benzenedoesnotreactwitheitherreagent.BenzenecanbepersuadedtoreactwithbromineifaLewisacidcatalayst

suchasFeBr3isadded,resultingintheformationofasubstitutionratherthanadditionproduct.一级同位素效应GeneralMechanismFree-energydiagramTheroleofLewisacids(FeCl3,FeBr3,AlCl3)–tomakebromine/chlorineabetterelectrophile.Anotherwaytoproduceamoreelectrophilicsourceofbromineistouseapyridinecatalyst.7.4.1Halogenation(卤化)Reactivityofhalogens(卤素的活性):F2>Cl2>Br2>I2Otheragents(其它试剂):IClRCOOXHOX

I2/HNO37.4.2Nitration(硝化)ThereactionTheelectrophileThemechanismNitroniumionApplication7.4.3Sulfonation(磺化)MechanismSulfonationalsotakesplaceinconcentratedsulfuricacidalone,butmoreslowly.Sulfonationareequilibria.

Desulfonationcanbeaccomplishedbyusingdilutesulfuricacid,orbypassingsteamthroughthereaction.ItispossiblethatthesulfonatingagentisnotprotonatedSO3butSO3itself.SulfonicacidsarestrongerthatHCl.氯磺酸苯磺酰氯0℃

43%4%53%100℃

13%8%79%7.4.4Friedel-Crafsalkylation(傅-克烷基化)CharlesFriedel(1832-1899)JamesMasonCrafts(1839-1917)MechanismActivityofLewisacids(路易斯酸的活性)AlCl3

>

FeCl3

>

SbCl5

>

SnCl4

>

BF3

>

TiCl4

>ZnCl2ThebaseAwrongmechanismOtherexamplesimpossiblereactionimpossiblestructureBoronhasfivebondsActivityofhalohydrocarbons(卤代烃的活性)叔卤代烷>苄基卤≈烯丙基卤≈仲卤代烷>伯卤代烷>甲基卤>乙烯基卤≈苯基卤RF>

RCl>

RBr

>

RIMechanismacylchlorideanhydride7.4.5Friedel-Crafsacylation(傅-克酰基化)Activityofreagents(试剂的活性):RCOCl>(RCO)2O

>

RCOOHActivityofsubstrates(底物的活性)×Y=NO2,N+Me3,CO2H,COR,CF3,SO3H,NH2,NHR,NR2QuantitiesofLewisacidInFriedel-Craftsalkylationsusinganalkylchloride,theLewisacidisusedincatalyticquantities;InFriedel-Craftsacylation,justoveroneequivalentofLewisacidpercarbonylgroupisrequired,becausetheLewisacidcancomplextothecarbonylintheproduct.LimitationsofFriedel-Craftsreactions.polyalkylationsoftenoccur.PolyacylationsarenotaprobleminFriedel-Craftsacylations.Friedel-Craftsalkylationcannotbeusedwithprimaryalkylhalides/alcohols:Rearrangement(重排)willoccur.Solution–Friedel-Craftsacylationfollowedbyreduction.Example:Arylandvinylhalidescannotbeusedasthehalidecomponentbecausetheydonotformcarbocations(unstable)readily.X√Oxygenandnitrogencanalsocomplextothecatalyst.Friedel-Craftsreactionusuallygivepooryieldswhenpowerfulelectron-withdrawinggroupsarepresentonthearomaticring.傅-克烷基化是可逆的7.4.6Blancchloromethylation(布朗克氯甲基化)Mechanism7.4.7Gattermann-Kochformylation(加特曼-科赫甲酰化)Mechanism烷基苯，酚，酚醚副反应较多，带有强钝化基的苯环不反应GattermannacylationH-C≡N+HCl→H-C+=NHCl-MechanismGattermannacylation适用于烷基苯，酚，酚醚6%93%1%

58%2%40%Activator(活化基)Deactivator(钝化基)o,p-Director(邻对位定位基)m-Director(间位定位基)7.5Directingeffectsofsubstituents(取代基的定位效应)Ortho&ParaDirectorsStrongActivators:

-O-,-NR2,-NHR,-NH2,-OH,-ORModerateActivators:

-NHCOR,-OCORWeakActivators:

-R,-C6H5,-CH=CHRWeakDeactivators:

-F,-Cl,-Br,-I,-CH2X,-CH=CHCOOH,-CH=CHNO2MetaDirectorsModerateDeactivators:

-CHO,-COR,-CO2R,-CO2H,-COXStrongDeactivators:

-CN,-SO3H,-NO2,-CF3,-CCl3,-N+R3ClassificationofSubstituentsinElectrophilicAromaticSubstitutionReactionsAllactivating

substituentsare

ortho,para

directors.

Halogensubstituentsareslightly

deactivating

butare

ortho,para-directing.

Strongly

deactivating

substituentsare

metadirectors.Twofactorsdecidethenatureofthedirectinggroup:Inductiveeffects.Resonanceeffect.InterpretationofdirectingeffectsMakingamineslessreactiveSelectivitybetweenorthoandparapositionsisdeterminedbysterichindranceAnexampleoforthoselectivity.Synthesisofsaccharin(糖精).Halo

Substituents:DeactivatingOrtho-ParaDirectors.Nitrationofhalobenzenes:Halobenzenesundergonitrationreactionsmuchslowerthanforbenzene.TherelativeratesfollowaU-shapedsequence.Thehalogroupsareortho-paradirectors.Thepercentageoftheorthoproductincreasesfromfluorobenzenetoiodobenzene–contrarytostericeffect.Multiplesubstituenteffects(多取代基效应)？1)取代基的定位效应一致时，它们的作用相互加强2)取代基的定位效应矛盾时,考虑活化基或邻对位定位基或弱钝化基3)不同类型的取代基相互处于间位时，第三个取代基主要进入间位定位基的邻位4)取代基定位能力相近时,得混合物1)傅-克烷基化，磺化是可逆反应2)活性较低(低于卤苯)的芳烃不起傅-克反应3)-NH2,-NHR,-NR3取代的芳烃不起傅-克反应4)乙烯型卤,芳基卤不能作为傅-克烷基化的试剂5)加特曼-科赫甲酰化反应,不能用烷基苯,酚,酚醚作底物,带有强钝化基的化合物不反应6)强活化的苯环会发生多卤代反应7.6Practice1)2)7.7Otherreactionsofbenzene(苯的其它反应)7.7.1AdditionofbenzenewithCl2(苯与氯的加成)7.7.2Halogenationofthebenzylicposition(苄基位的卤化)7.7.3Oxidation(氧化)OxidationofthesidechainKMnO4HNO3Na2Cr2O7含α氢MechanismOxidationofthebenzenering7.7.4Reduction(还原)Catalytichydrogenation(催化氢化)Birchreduction(伯齐还原)Thereaction:Sodiumamide,NaNH2,ismadebydissolvingNainliquidNH3.Mechanismconjugateddiene,morestable.kineticproduct,lessstable.Regioselectivity–electron-withdrawinggroupspromoteipso,parareductionwhileelectron-donatinggroupspromoteortho,metareduction.当苯环上连有烯键时，若烯键与苯环共轭，则烯键首先被还原Conjugateddienesbyisomerization.Withanilines,itisimpossibletostoptheisomerizationtakingplaceduringthereaction,andBirchreductionalwaysgivesconjugatedenamines.7.8Polycyclicarenes(多环芳烃)7.8.1Multiphenylaliphatichydrocarbons(多苯代脂烃)2,2-二(4-氯苯基)-1,1,1-三氯乙烷反应深红碳正离子的稳定性Ph3C+

>Ph2CH+

>R3C+>PhCH2+≈R2CH+≈CH2=CHCH2+>RCH2+>CH3+>CH2=CH+≈Ph+自由基的稳定性Ph3C•

>Ph2CH•

>PhCH2•

≈CH2=CHCH2•

>

R3C•

>

R2CH•>RCH2•>CH3•>CH2=CH•≈Ph•7.8.2Biphenyls(联苯类)6’6123451’2’3’4’5’2,4’-二氯联苯2-氯-4’-硝基联苯4-(3-氨基苯基)-2-氯苯甲醛制备-Ullmann反应反应7.8.3Fused-ringarenes(稠环芳烃)菲萘蒽123456781012345678910123456789αβγαβ1-硝基萘5-甲基-2-萘磺酸1,6-萘二胺α-硝基萘芘苯并[a]芘蔻AfullereneAportionofananotubeGraphene(石墨烯)isaone-atom-thickplanarsheetofsp2-bondedcarbonatomsthataredenselypackedinahoneycombcrystallattice.Itcanbevisualizedasanatomic-scalechickenwiremadeofcarbonatomsandtheirbonds.Grapheneisthebasicstructuralelementofsomecarbonallotropes(同素异形体)includinggraphite,carbonnanotubesandfullerenes.Itcanalsobeconsideredasaninfinitelylargearomaticmolecule.TheNobelPrizeinPhysicsfor2010wasawardedtoAndreGeimandKonstantinNovoselov“forgroundbreakingexperimentsregardingthetwo-dimensionalmaterialgraphene”.化学反应还原反应氧化反应加成反应亲电取代反应easiertoformmorestable定位规律萘发生亲电取代时，环上的活化基使取代多发生在同环活化基在1位时，取代多发生在4位活化基在2位时，取代多发生在1位，也可能发生在6位(在异环)钝化基使取代多发生在异环卤化，硝化多发生在α位(同时考虑位阻效应)磺化，酰化多发生在β位蒽作为二烯体与亲二烯体发生D-A反应萘及其衍生物的合成-Haworth反应蒽及其衍生物的合成菲及其衍生物的合成Areallfully-conjugated,cyclicsystems(calledannulenes轮烯)aromatic?√√7.9Hückel’sRuleandAromaticity(休克尔规则与芳香性)7.9.1Hückel’sRule

AmoleculeisaromaticifitIscyclicandplanarIscompletelyconjugatedContains4n+