2013chapterVI.ppt

1 chapte6 anoverviewoforganicreactions properuseofcurvedarrowstoillustratemechanisms qualitativeunderstandingof g theuseofenergydiagramstodescribereactions keyfocus 2 6 1kindsoforganicreactions有机反应类型 commonpatternsdescribethechangesinorganicreactions 2reactantsaddtogethertoformasinglenewproduct additionreactions加成反应 3 2reactantsexchangepartstogive2newproducts eliminationreactions消去反应 asinglereactantsplitinto2products substitutionreactions取代反应 4 asinglereactantundergoesareorganizationofbondstoyieldanisomericproduct rearrangementreactions重排反应 dihydroxyacetonephosphate glyceraldehyde3 phosphate kindsoforganicreactions有机反应类型 5 6 2howorganicreactionsoccur reactionmechanisms reactionsoccurindefinedstepsthatleadfromreactanttoproduct themechanismdescribesthestepsbehindtheobservedchangesinareaction weclassifythetypesofstepsinasequence astepinvolveseithertheformationorbreakingofacovalentbond stepscanoccurindividuallyorincombinationwithothersteps whenseveralstepsoccuratthesametimetheyaresaidtobeconcerted协同 反应机理 6 symmetrical homolyticbreakage均裂 unsymmetrical heterolyticbreakage异裂 reactionmechanisms反应机理 bondbreaking键的断裂andbondforming键的形成 bondformationorbreakagecanbesymmetricalorunsymetrical symmetricalbond breaking radical自由基 onebondingelectronstayswitheachproduct unsymmetricalbond breaking polar极性 twobondingelectronsstaywithoneproduct symmetricalbond making radical自由基 onebondingelectronisdonatedbyeachreactant unsymmetricalbond making polar极性 twobondingelectronsaredonatedbyonereactant 7 indicatebreakingandformingofbonds arrowheadswitha half head fish hook鱼钩 indicatehomolyticandhomogenicsteps radicalprocesses arrowheadswithacompleteheadindicateheterolyticandheterogenicsteps polarprocesses reactionmechanisms反应机理 bondbreaking键的断裂andbondforming键的形成 curvedarrows弯曲箭头 8 6 3radicalreactions自由基反应 aradicalcanbreakabondinanothermoleculeandabstractapartnerwithanelectron givingsubstitutionintheoriginalmolecule aradicalcanaddtoanalkenetogiveanewradical causinganadditionreaction radicalsreacttocompleteelectronoctetofvalenceshell 9 aradicalcanachieveavalence shelloctetinseveralways aradicalsubstitutionreaction自由基取代反应 aradicaladditionreaction自由基加成反应 radicalreactions自由基反应 10 threetypesofsteps initiation引发 propagation传递 termination终止 methanechlorinechloromethane radicalchlorinationreactions自由基氯代反应 11 initiation引发 homolyticformationoftworeactivespecieswithunpairedelectrons methanechlorinechloromethane radicalchlorinationreactionmechanism自由基氯代反应机理 12 radicalchlorinationreactionmechanism自由基氯代反应机理 methanechlorinechloromethane propagation传递 reactionwithmoleculetogeneratenewradical 13 termination终止 combinationoftworadicalstoformastableproduct radicalchlorinationreactionmechanism自由基氯代反应机理 methanechlorinechloromethane 14 o2 oxygenradical carbonradical thesynthesisofprostaglandins合成前列腺素 15 6 4polarreactions极性反应 differenceinelectronegativitiescausesapartialnegativechargeonanatomandacompensatingpartialpositivechargeonanadjacentatom themoreelectronegativeatomhasthegreaterelectrondensity bondpolarity elementssuchaso f n clmoreelectronegativethancarbon 16 polaritypatternsinsomecommonfunctionalgroups 醇 烯烃 卤代烃 胺 羰基 羧酸 酰氯 醛 17 polaritypatternsinsomecommonfunctionalgroups 醚 硫醚 腈 格氏试剂 烷基锂试剂 酯 酮 18 polarizationisachangeinelectrondistributionasaresponsetoachangeinelectronicnatureofthesurroundings polarizabilityisthetendencytoundergopolarization polarreactionsoccurbetweenregionsofhighelectrondensityandregionsoflowelectrondensity electronegativityvaluesofc sandiareall2 5 polarizability极化度 可极化性 19 anelectrophile亲电试剂 anelectron poorspecies combineswithanucleophile亲核试剂 anelectron richspecies electrophile lewisacidnucleophile lewisbase generalizedpolarreaction极性反应 20 somenucleophilesandelectrophiles electrostaticpotentialmapsidentifythenucleophilic negative andelectrophilic positive atoms 21 6 5anexampleofapolarreaction additionofhbrtoethylene the bondiselectron rich nucleophileh briselectrondeficientath electrophile 22 electrophilicadditionreactionofethyleneandhbr乙烯与氢溴酸的亲电加成反应 23 reactionmechanisms反应机理 ch2 ch2 hbrch3ch2br 24 6 6usingcurvedarrowsinpolarreactionmechanisms极性反应机理 curvedarrowsareawaytokeeptrackofchangesinbondinginpolarreaction thearrowstrack electronmovement electronsalwaysmoveinpairs chargeschangeduringthereaction onecurvedarrowcorrespondstoonestepinareactionmechanism 25 electronsmovefromanucleophilicsourcetoanelectrophilicsinki e electronswould want toflowfromregionofhighelectrondensitytoregionoflowelectrondensity arrowswillalwayspointawayfromnegativechargesandtowardpositiveones someguidelines 26 therulesandcommonpatterns rule1 electronsmovefromanucleophilicsource nu ornu toanelectrophilicsink eore thenucleophilicsourcemusthaveanelectronpairavailable usuallyeitherasalonepairorinamultiplebond theelectrophilicsinkmustbeabletoacceptanelectronpair usuallybecauseithaseitherapositivelychargedatomorapositivelypolarizedatominafunctionalgroup electronsusuallyflowfromoneofthesenucleophiles亲核 electronsusuallyflowtooneoftheseelectrophiles亲电 27 rule2 thenucleophile亲核试剂canbeeithernegativelychargedorneutral thetotalchargeononesideofthetransformationarrowmustbethesameasontheotherside 28 rule3 theelectrophile亲电试剂canbeeitherpositivelychargedorneutral thetotalchargeononesideofthetransformationarrowmustbethesameasontheotherside 29 rule4 theoctetrule八隅律mustbefollowed 30 additionalpointstonote mcmurry preferred wrong 31 positionofarrows 32 6 7describingareaction equilibria rates andenergychanges theratioofproductstoreactantsisdependentontheirrelative energycontent mathematically forareaction forexample 33 enthalpy 焓 changeenergyof bondsbroken bondsformed ve exothermic ve endothermic entropy 熵 change moleculardisorder混乱度of products reactants g 自由能 istheenergydifferencebetweenreactants反应物andproducts产物 ve exergonic放热 ve endergonic吸热 34 note equilibriumpositionofareaction rateofareaction explanationofthermodynamicquantities dg dh tds rate isthereactionfastorslow equilibrium inwhatdirectiondoesthereactionproceed 35 theratioofproductstoreactantsiscontrolledbytheirrelativegibbsfreeenergy自由能 thechangeingibbsfreeenergybetweenproductsandreactantsiswrittenas g gibbsfreeenergyandk 36 theenergyfromformingabondcanbedescribedbyitsbonddissociationenergy bde 键离解能 gibbsfreeenergyandk example 37 6 8describingareaction bonddissociationenergies键离解能 bonddissociationenergy d amountofenergyrequiredtobreakagivenbondtoproducetworadicalfragmentswhenthemoleculeisinthegasphaseat25 c theenergyismostlydeterminedbythetypeofbond independentofthemolecule changesinbondscanbeusedtocalculatenetchangesinheat 38 somebonddissociationenergies d 39 somebonddissociationenergies d 40 6 9describingareaction 能量图和过渡态energydiagramsandtransitionstates g g agoodwaytovisualizetheenergychangesthroughoutthecourseofareaction 41 6 10describingareaction intermediates中间体 recall ifareactionoccursinmorethanonestep itmustinvolvespeciesthatareneitherthereactantnorthefinalproduct thesearecalledreactionintermediatesorsimply intermediates中间体 eachstephasitsownfreeenergyofactivation活化自由能 thecompletediagramforthereactionshowsthefreeenergychangesassociatedwithanintermediate 42 43 44 5 11acomparisonbetweenbiologicalreactionsandlaboratoryreactions laboratoryreactionsusuallycarriedoutinorganicsolvent biologicalreactionsinaque