鄭州大學 有機化學7芳香烴

Chapter7AromaticHydrocarbonsHydrocarbons(烴)Aliphatic~(脂肪烴)Alicyclic~(脂環(huán)烴)Aromatic~,arenes(芳香烴)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(單環(huán)芳香烴)Biphenyls(聯(lián)苯類)

Multiphenylaliphatichydrocarbons(多苯代脂肪烴)Fused-ringarenes(稠環(huán)芳香烴)Nonbenzenoidsystem(非苯體系)Heterocycliccompounds(雜環(huán)化合物)7.1Structureofbenzene(苯的結構)Kekuléstructure“Butlook!Whatwasthat?Oneofthesnakeshadseizedholdofitsowntail,andtheformwhirledmockinglybeforemyeyes.Then,asifbyaflashoflightningIawoke.”Itremainschemistry'smostfamousahamoment.“Letuslearntodream,thenperhapsweshallfindthetruth.”Kekulésuggestedthattwoisomericstructurescouldexistbutinterconvertedtoorapidlytobeseparated.Tautomerism(互變異構)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)苯作為母體甲(基)苯異丙苯氯(代)苯硝基苯1,2-二甲苯1-甲基-3-乙基苯1-甲基-4-叔丁基苯鄰二甲苯間甲乙苯對甲叔丁苯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

1,2,4-三甲苯連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為取代基苯基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

-苯基丙酸鄰苯二甲酸酐苯胺對苯二酚間苯二胺1-苯基乙醇苯磺酸基團的重要性-COOH>-SO3H>-COOR>-COX>-CONH2>-OCOR>-CN>-CHO>-COR>-OH>-NH2>-OR>-R>-X>-NO2>-NO對硝基氯苯鄰羥基苯甲酸鄰乙酰氧基苯甲酸

水楊酸乙酰水楊酸(阿司匹林)苯乙酮鄰乙?；郊姿峒柞?.3Physicalpropertiesofbenzene(苯的物理性質(zhì))7.4Reactionsofbenzene-Electrophilicsubstitution(親電取代)Reactionofsimplealkeneswithelectrophiles:

Underthesameconditions,benzenedoesnotreactwitheitherreagent.BenzenecanbepersuadedtoreactwithbromineifaLewisacidcatalayst

suchasFeBr3isadded,resultingintheformationofasubstitutionratherthanadditionproduct.一級同位素效應GeneralMechanismFree-energydiagramTheroleofLewisacids(FeCl3,FeBr3,AlCl3)–tomakebromine/chlorineabetterelectrophile.Anotherwaytoproduceamoreelectrophilicsourceofbromineistouseapyridinecatalyst.7.4.1Halogenation(鹵化)Reactivityofhalogens(鹵素的活性):F2>Cl2>Br2>I2Otheragents(其它試劑):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(鹵代烴的活性)叔鹵代烷>芐基鹵≈烯丙基鹵≈仲鹵代烷>伯鹵代烷>甲基鹵>乙烯基鹵≈苯基鹵RF>

RCl>

RBr

>

RIMechanismacylchlorideanhydride7.4.5Friedel-Crafsacylation(傅-克?；?Activityofreagents(試劑的活性):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?；?Mechanism烷基苯，酚，酚醚副反應較多，帶有強鈍化基的苯環(huán)不反應GattermannacylationH-C≡N+HCl→H-C+=NHCl-MechanismGattermannacylation適用于烷基苯，酚，酚醚6%93%1%

58%2%40%Activator(活化基)Deactivator(鈍化基)o,p-Director(鄰對位定位基)m-Director(間位定位基)7.5Directingeffectsofsubstituents(取代基的定位效應)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(多取代基效應)？1)取代基的定位效應一致時，它們的作用相互加強2)取代基的定位效應矛盾時,考慮活化基或鄰對位定位基或弱鈍化基3)不同類型的取代基相互處于間位時，第三個取代基主要進入間位定位基的鄰位4)取代基定位能力相近時,得混合物1)傅-克烷基化，磺化是可逆反應2)活性較低(低于鹵苯)的芳烴不起傅-克反應3)-NH2,-NHR,-NR3取代的芳烴不起傅-克反應4)乙烯型鹵,芳基鹵不能作為傅-克烷基化的試劑5)加特曼-科赫甲?；磻?不能用烷基苯,酚,酚醚作底物,帶有強鈍化基的化合物不反應6)強活化的苯環(huán)會發(fā)生多鹵代反應7.6Practice1)2)7.7Otherreactionsofbenzene(苯的其它反應)7.7.1AdditionofbenzenewithCl2(苯與氯的加成)7.7.2Halogenationofthebenzylicposition(芐基位的鹵化)7.7.3Oxidation(氧化)OxidationofthesidechainKMnO4HNO3Na2Cr2O7含α氫MechanismOxidationofthebenzenering7.7.4Reduction(還原)Catalytichydrogenation(催化氫化)Birchreduction(伯齊還原)Thereaction:Sodiumamide,NaNH2,ismadebydissolvingNainliquidNH3.Mechanismconjugateddiene,morestable.kineticproduct,lessstable.Regioselectivity–electron-withdrawinggroupspromoteipso,parareductionwhileelectron-donatinggroupspromoteortho,metareduction.當苯環(huán)上連有烯鍵時，若烯鍵與苯環(huán)共軛，則烯鍵首先被還原Conjugateddienesbyisomerization.Withanilines,itisimpossibletostoptheisomerizationtakingplaceduringthereaction,andBirchreductionalwaysgivesconjugatedenamines.7.8Polycyclicarenes(多環(huán)芳烴)7.8.1Multiphenylaliphatichydrocarbons(多苯代脂烴)2,2-二(4-氯苯基)-1,1,1-三氯乙烷反應深紅碳正離子的穩(wěn)定性Ph3C+

>Ph2CH+

>R3C+>PhCH2+≈R2CH+≈CH2=CHCH2+>RCH2+>CH3+>CH2=CH+≈Ph+自由基的穩(wěn)定性Ph3C?

>Ph2CH?

>PhCH2?

≈CH2=CHCH2?

>

R3C?

>

R2CH?>RCH2?>CH3?>CH2=CH?≈Ph?7.8.2Biphenyls(聯(lián)苯類)6’6123451’2’3’4’5’2,4’-二氯聯(lián)苯2-氯-4’-硝基聯(lián)苯4-(3-氨基苯基)-2-氯苯甲醛制備-Ullmann反應反應7.8.3Fused-ringarenes(稠環(huán)芳烴)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(同素異形體)includinggraphite,carbonnanotubesandfullerenes.Itcanalsobeconsideredasaninfinitelylargearomaticmolecule.TheNobelPrizeinPhysicsfor2010wasawardedtoAndreGeimandKonstantinNovoselov“forgroundbreakingexperimentsregardingthetwo-dimensionalmaterialgraphene”.化學反應還原反應氧化反應加成反應親電取代反應easiertoformmorestable定位規(guī)律萘發(fā)生親電取代時，環(huán)上的活化基使取代多發(fā)生在同環(huán)活化基在1位時，取代多發(fā)生在4位活化基在2位時，取代多發(fā)生在1位，也可能發(fā)生在6位(在異環(huán))鈍化基使取代多發(fā)生在異環(huán)鹵化，硝化多發(fā)生在α位(同時考慮位阻效應)磺化，酰化多發(fā)生在β位蒽作為二烯體與親二烯體發(fā)生D-A反應萘及其衍生物的合成-Haworth反應蒽及其衍生物的合成菲及其衍生物的合成Areallfully-conjugated,cyclicsystems(calledannulenes輪烯)aromatic?√√7.9Hückel’sRuleandAromaticity(休克爾規(guī)則與芳香性)7.9.1Hückel’sRule

AmoleculeisaromaticifitIscyclicandplanarIscompletelyconjugatedContains4n+