生物学生物化学

1、会计学1生物学生物化学生物学生物化学陈立C C H H3 3B B e en nz ze en ne eT To ol l u ue en ne eN N a ap ph ht th ha al l e en ne ebenzene.苯甲苯三苯甲烷萘CH33CHCH3CH3CH3CHCH2苯甲苯1,2二甲苯苯乙烯烷基取代的苯称为烃基苯。取代基是烷基的，叫烷基苯。苯的结构可以是一种“环己三烯”类型的的结构，但苯的性质却表现出与环状烯烃大相径庭的性质。ReagentsCyclohexeneBenzeneKMnO4/H2OBr2/CCl4HI 1202313120=360208“”苯的氢化热低于假设

2、中的“环己三烯”的推算数值,说明苯比设想的“环已三烯”稳定PtC H3C O O H30 C+ 3 H2H = -208.5 K J/ m ol e2-3 atm PressuerH H2 2 + +2 2 H H2 2 + + + 3 3 H H2 2+ + 3 3 H H2 2E En ne er rg gy ya a r r e ea al l m mo o l le ec cu ul la ar r, ,b be e n nz ze en n e ea an n i im ma ag gi in na ar ry y m mo ol le ec cu ul la ar r, ,c cy

3、 yc cl lo oh he ex xa at tr ri ie en ne eHeat of hydrogenation of cyclogenation of cyclohexene, 1,3-cyclohexadiene, a hypothetical 1,3,5-cyclohextriene, and benzene. ( KJ/mole)1201523120=360231208Inwhichall6Catomsin“aromatic”ringaresp2hybridised,withremaining6e-inunhybridisedporbitalsdelocalisedover

4、entirering,formingdoughnut/torusshapede-cloudsabove&belowringplanelAll12atomsinbenzene,C6H6,lieinthesameplane.lBenzenehasaplanar,cyclic,conjugatedstructure.lIfonedrawsbenzeneasalternatingC=CandC-CthenthetwodifferentKekulstructuresareobtained.lThesearetwoequallyvalidresonancecontributors.lAlternative

5、ly,thesetwoformscanbecombinedintheresonancehybridandthepsystemrepresentedbyacircleasintheRobinsonstructure.lNotethatalloftheC-Cbondsare1.4(betweentypicalC=CandC-Cdistances).H HH H1 10 08 8p pm m1 14 40 0p pm m1 12 20 0C CC CC CC CC CC CH HH HH HH HH HH HlKekul的两种结构式符合共振条件：两种结构式仅在电子排列上结构不同l根据共振理论,苯是，

6、的杂化体，由于二式完全等同，因此具有相同的稳定性，对杂化体的参与程度相等,共振作用大大提高了苯识所引起的稳定性i i s s e eq qu ui i v va al l e en nt t t to o现在仍普遍地采用Kekul结构式表示苯环结构，但必须意识到其中碳碳单键和双键由于电子在闭合共轭体系中充分离域的结果，两者是完全等同的，是没有区别的。RobinsonStructureC CC CC CC CC CC CH HH HH HH HH HH H苯分子中每个碳均采用sp2杂化，各个碳，氢均处于同一平面中。C CC CC CC CC CC CH HH HH HH HH HH HTheim

7、ageshowstheelectrostaticpotentialforbenzene.Benzeneismuchmorestablethanwouldbeexpectedbasedoncalculationsfor“cyclohexatriene”Areasonablepredictionfortheheatofhydrogenationofhypotheticalcyclohexatrieneis-360kJmol-1(3timesthatofcyclohexene,-120kJmol-1)Theexperimentallydeterminedheatofhydrogenationforb

8、enzeneis-280mol-1,152kJmol-1morestablethanhypotheticalcyclohexatrieneThisdifferenceiscalledtheresonanceenergyNomenclature:Functionalgroupsuffix=-benzene (review)Functionalgroupprefix=phenyl-Substitutedbenzenesareusuallynamedassuch.Therelativepositionscanbedenotedas1,2-=ortho-,1,3-=meta-and1,4-=para-

9、substitution.Whenpolysubstituted,thenumbersaloneareused,e.g.1,2,3-trimethylbenzeneortho(o)-邻1,2-meta(m)-间1,3-para(p)-对1,4-121231234ortho(o)-Xyl ene1,2-dim ethyl benzenem eta(m )-Xylene1,3-dim ethylbenzenepara(p)-Xyl ene1,4-di m ethylbenzene12123C H3C H3C H3C H3H3CCH31234邻二甲苯间二甲苯对二甲苯1,2,3-tri m ethyl

10、benzenevic1,2,4-trim ethyl benzeneunsym1,3,5-trim ethylbenzenesym12234C H3C H3C H3C H3C H313C H3H3CC H3H3C513连三甲苯偏三甲苯均三甲苯StructureNameStyrene苯乙烯Acetophenone苯乙酮Phenol苯酚Anisole苯甲醚Aniline苯胺C CH HC CC CH H3 3O OH HO OC CH H3 3N NH H2 2C CH H2 2O OOHOCH3NH2CH3phenoltolueneanilineanisoleCHCH2COCH3COHCOOHs

11、tyreneacetophenonebenzaldehydebenzoic acid351215123N H2C H OC lN O2SO3HN H2O HBrO H3-am ino-5-brom ophenol3-氨基-5-溴苯酚2-am ino-5-hydroxybenzaldehyde2-氨基-5-羟基苯甲醛2-chloro-3-ni tro benzenesulfonicacid3-硝基-2-氯苯磺酸 联苯型CH2CH2CH芳基烷型 萘蒽菲naphthal eneanthracenePhenanthreneIntheabsenceofpolarsubstituents,arenesar

12、etypicalofhydrocarbons:lowmeltingandboilingpoints,lowsolubilityinpolarsolvents.Meltingpoints:Moresymmetricalthancorrespondingalkane,packbetterintocrystals,sohighermeltingpoints.Boilingpoints:Dependentondipolemoment,soorthometapara,fordisubstitutedbenzenes.Density:Moredensethannonaromatics,lessdenset

13、hanwater.Solubility:Generallyinsolubleinwater.BenzenecanbeinducedtoreactwithbromineifaLewisacidcatalystispresenthoweverthereactionisasubstitution andnotanadditionBenzeneproducesonlyonemonobrominatedcompound,whichindicatesthatall6carbon-hydrogenbondsareequivalentinbenzeneMetal-ammonia-alcoholreductio

14、nsofaromaticringsareknownasBirchreductions.+2 N a +2 C H3O HN H3+2 N aO C H3N a,N H3C(C H3)3C (C H3)3C H3C H2O HA l kyl-substi tuted arenes give 1,4-cyclohexadi enes i n w hich the alkylgroup i s substi utenton the doubl e bond.与苯环共轭的双键首先发生Birch还原N a,N H3CC (C H3)3C H3C HC H3C H3CH2C H3C H2O HN a,N

15、H3C H3C H2O H不与苯环共轭的双键不发生Birch还原N a,N H3C H2CHC H2C H2CHC H2C H3C H2O H Themechanism:Step1:C H3C l2LightO rH eatC l2LightO r H eatC H2C lC H C l2C l2LightO rH eatC C l3C lC lhv2 C lStep2:Benzylradical苯甲基(苄基)自由基Afterhomolysis(均裂)ofthebenzylicC-Hbond,theunpairedelectronissharedbybenzyliccarbonandbythe

16、ringcarbonsthatareorthoandparatoit.CH2HC H2+H C lC lC H2CH2C H2C H2Benzylradicalisstabilizedbyoverlapofitshalf-filledporbitalwiththesystemofthearomaticring.H Ha al lf f- -f fi il ll le ed dp p o or rb bi it ta al lStep3:CH2C lCH2C lSuccinimiden.琥珀酰亚胺CH (C H3)2Br2hvC B r(C H3)2C H2C H3+N B rOOCH CH3+

17、N HOOCC l4H eatB r C H2RN a2Cr2O7H2O ,H2SO4H eatC O O HCH R2Noteregardlessofchainlengthofalkylgroups,alkylgroupsconvertedtocarboxylgroups(-COOH)attacheddirectlytothering. C (C H3)3K M nO4(CH3)3C C O O H ArC H2C lN aC NC H3C H2O H -H2OC H3C O O N aC H3C O O HA rC H2CNA rCH2O C O C H3 styreneEN uN aoE

18、tN uERelatedreactionsElectrophilicadditionsreactionsofalkenesaq. H2SO4O HC lH C l Reactiontype:Elimination(E1orE2)LGHstyreneRelatedreactionsDehydrationofalcoholsDehydrohalogenationofallylhalidesO HstyreneC lN aoEtH2SO4H eat1-(1-chl oroethyl )benzene1-phenyl ethanollBenzylicalcoholsundergoacidcatalyz

19、eddehydrationreadilyviaanE1pathwaytoformconjugatedalkenes.lBenzylichalidesundergobasecatalyseddehydrohalogenationviaanE2pathwaytoformconjugatedalkenes.Summary Amongplanar(平面的)monocyclicfullyconjugatedpolyenesonlythosepossessing(4n+2)electrons,willhavespecialaromaticstability.芳香性(Aromaticity)：l 在闭合共轭

20、多烯体系中;l 成环原子共平面；l 电子数符合 4n + 2 +n = 0 n = 1 n = 1 n = 1 n = 2BHNNN+OSn = 0 n = 1 n = 1 n = 1 n = 2O84n+2=10(平面八边型有芳香性)+ + 2 2 K K2 2 - -+ + 2 2 K K4 H CC HN i (C N )2H eat, Pressure4+ + H H + +Cyclopendiene环戊二烯:活泼,具备烯烃性质Cyclopentadieneisunusuallyacidic(pKa=16)becauseitbecomesthearomaticcyclopentadie

21、nylanionwhenaprotonisremovedCyclopentadienylanionhas6pelectronsinacyclic,continuousp-electronsystem,andhencefollowsthe4n+2ruleforaromaticityB r2B rB r-H B rB rCyaloheptrienylcation4n+2=6稳定pKa=36(1Z,4Z)-3,6-di brom ocycl ohepta-1,4-di ene(1Z,3Z,5Z)-cycl ohepta-1,3,5-tri ene4n+2=2- -H H + +Cyclopropen

22、ylcation(环丙烯正离子):4n+2=184n+2=1818162 2 - - Nonbenzenoidaromaticcompoundsdonotcontainbenzenerings Examplesarecyclopentadienylanionandthearomaticannulenes(except6annulene) Azulene(奥,甘菊环)hassubstantialresonanceenergyandalsosubstantialseparationofcharge,asshownintheelectrostaticpotentialmapNonbenzenoid

23、Aromatic CompoundsExamples of Important NitrogenHeterocyclic Aromatic CompoundsNNNNNNHPyrimidinePurineNNNNNH2HAdenineNNNNONH2HHGuanineNNOOHHThymineNNONH2HCytosinen二苯甲烷C C6 6H H6 6 + + C C6 6H H5 5C C H H2 2C C l lA A l l C C l l3 32 2 C C6 6H H6 6 + + C C H H2 2C C l l2 2A A l l C C l l3 3C C H H2 2

24、C C H H2 2H H2 2C C r rO O4 4B B r r2 2C C6 6H H5 5C C H H C C6 6H H5 5B B r rC C6 6H H5 5C C C C6 6H H5 5O O3 3 C C6 6H H6 6 + + C C H H C C l l3 3A A l l C C l l3 3( (C C6 6H H5 5) )3 3C C H H + + H H C C l lH H2 2C C r rO O4 4B B r r2 2C C6 6H H5 5C C C C6 6H H5 5O O H H( (C C6 6H H5 5) )3 3C C H

25、 H( (C C6 6H H5 5) )3 3C C B B r r( (C C6 6H H5 5) )3 3C C H H( (C C6 6H H5 5) )2 2C C H H2 2K K N N H H2 2N N H H3 3( (l l ) )( (C C6 6H H5 5) )3 3C C K K( (C C6 6H H5 5) )2 2C C H H K K4,4-二硝基联苯1 12 23 34 45 56 61 1 6 65 5 4 4 3 3 2 2 o om mo o m m p p p pN N O O2 2O O2 2N N苯环上有吸电基(-NO2,-CN)，对反应有利

26、2 2 C C6 6H H5 5I I + + 2 2 C C u uC C6 6H H5 5C C6 6H H5 5Ullmann Reaction:位阻异构现象(Atropisomerism):分子单键之间的自由旋转受到阻碍时而产生的光活性异构体的现象C CO OO O H HH HO O O OC CO O2 2N NN NO O2 2O O2 2N NN NO O2 2C CO O O OH HH HO OO O C CN N O O2 2O O2 2N NO O2 2N NC C O O O O H HH H O O O O C CN N O O2 2N N O O2 2O O2 2

27、N NX X1 1X X4 4X X2 2X X3 3Adoms规则：只要25以下C-X1+C-X2ORC-X3+C-X42.9就可能存在光学活性X X1 1X X4 4X X2 2X X3 3C-XC-XC-HC-CH3C-COOHC-NH2C-NO2C-OH0.94-1.041.51.561.561.921.45C-OCH3C-FC-ClC-BrC-I1.451.391.691.882.00Ingeneral,polycyclicaromaticsaremorereactivethanbenzene.1 12 23 34 45 56 67 78 88 87 76 65 51 10 09 9

28、4 43 32 21 1 N Na ap ph ha al le en ne e A An nd dt th hr ra ac ce en ne e P Ph he en na an nt th hr re en ne e8 87 76 65 51 10 09 94 43 32 21 1Thechemistryofthesesystemsissimilartothatoftheparentbenzene,buttheyareusuallymorereactivethanbenzene.Evidenceforthiscanbeseenintheresonanceenergydatawhichsh

29、owsthattheirresonanceenergiesarelessthanthesamenumberofisolatedbenzenes.CompoundNameLineDrawingResonanceEnergyBenzene152kJ/mol36kcal/molNaphthalene255kJ/mol61kcal/molAnthracenePhenanthrene347kJ/mol83kcal/mol381kJ/mol91kcal/molLengthofC-Cbond:(ppm)Naphthalene 1 12 23 34 45 56 67 78 81 13 36 6. .3 31

30、14 42 2. .3 31 14 42 2. .1 11 14 41 1. .8 8lOxidationofNaphthalene:1,4-萘醌邻苯二甲酸酐lTheResonancesofC C r rO O3 3- -H H O O A A c cV V2 2O O5 5, , a ai i r r4 40 00 0- -5 50 00 0 C CO OO OO OO OO ON N H H2 2N N O O2 2 O O O O C C O O O O H HC C O O O O H HN N O O2 2C C O O O O H HC C O O O O H HN N H H2

31、2 O O C C O O O O H HC C O O O O H HN N O O2 2C C O O O O H HC C O O O O H HC C H H3 3取代反应主要在位上发生 H H N N O O3 3H H2 2S SO O4 4, , 5 50 0 C CN N O O2 2+ + H H2 2O O B B r r2 2C C H H3 3C C O O O O H H C C l l2 2, ,I I2 2 C C6 6H H6 6B B r rC C l l取代热力学控制取代动力学控制S SO O3 3H HH H2 2S SO O4 41 16 60 0 C

32、C6 60 0 C CS SO O3 3H H主主次次G G ( (o o, ,p p) )G G ( (o o, ,p p) )G G ( (m m ) )G G ( (m m ) )C C l l2 2C C l lC C l lC C l l2 2C C l lH H C C l lC C l lC C l lC C l lC C l lH H C C l lC C l lC C l llTheCatalyzedHydrogenationofNaphthalene十氢萘顺十氢萘反十氢萘C C H H3 3+ + C C l l2 2 I I2 2C C6 6H H6 6C C H H3 3C C l lH HH HH HH H顺型为主反型为主H H2 2N N i iH H2 2P Pt tB B i i r rc ch h R R e ed du uc ct ti i o on n N N a a o or r K K . . L Li iN N H H3 3( (l l ) ), ,C C H H3 3C C H H2 2O O H H N N a a o or r K K . . L Li iN N H H3 3( (l l ) ), ,C C H H3 3C C H H2 2O O H H8 87 7