2019春季物理有机化学chapter

1、Arreheniusacid-Acid: proton donor Arreheniusacid-Acid: proton donor Brnsted-Lowryacid-Acid: proton donor Base:protonacceptorLewisacid-Acid:electronpairacceptor Base: electron pair donor2Theprotonic(Brnsted-Lowry)definitionBrnsted,J.N.Rec.Trav.Theprotonic(Brnsted-Lowry)definitionBrnsted,J.N.Rec.Trav.

2、Chim.Pays-Bas1923,42,718;Lowry,T.M.Chem.Ind.1923,42,TheBrnsted-Lowrydefinition,formulatedindependentlybyitstwo proponents, revolves around an acids ability to donate protons (H+) to another compound, called a base, in a chemical reaction.Conjugateacidand conjugate OO+conjugate conjugate3General A(m-

3、AnacidisaprotonAbaseisaprotonconjugate baseconjugate acidEq.5.2 O+-4O+OO+ n-+n-HOO+-4O+OO+ n-+n-HOOAnymoleculecontaininghydrogenisapotentialBrnstedacid, whereas any molecule at all is a potential Brnsted base任何带氢的分子都是潜在的Brnsted酸任何分子都是潜在的Brnsted碱非酸溶剂：全氟、全氯溶剂CF2ClCFCl2,4Lyoniumion溶剂阳离子protonatedsolven

4、tLyateionLyoniumion溶剂阳离子protonatedsolventLyateion溶剂阴离子theconjugatebaseofany-*Thestructureofthesolvent-protonclusters(studiedwithMSin gas phase)n5H=-171kcalmol-1 H = -32 kcalmol-1Upto8waterAqueous+ A+B+H3+O A-=5.2.1HAAqueous+ A+B+H3+O A-=5.2.1HA H 2aH3+O A-=HA H3+O A-=H3+O A-pKa = -log 6Thermodynamic

5、 B+HO-=B+HO-=7When the pH is the same as the acids pKa, the solution has the same ability to protonatetheconjugatebaseWhen the pH is the same as the acids pKa, the solution has the same ability to protonatetheconjugatebaseA- astheacid hastheability to protonate thesolvent,andhencetheacidexistsasa1:1

6、ratioofitsandA- WhenthepHisabovethepKa, thesolutiondoesveenoughabilitytoprotonatetheconjugatebase,and thereforetheacidmostlyinitsconjugatebaseformA-WhenthepHisbelow thepKa,thedonorabilityofthesolution strongenoughtoprotonateA-,andmostlyHA8指示剂：共轭结指示剂：共轭结构发生变化9TheLevelingNo acidntheconjugateacid ofa s

7、olvent canexistTheLevelingNo acidntheconjugateacid ofa solvent canexistblehat solvent（比溶剂的共轭酸更强的酸不以较高浓度存在No basentheconjugatebaseofa solventcanexistblehat solvent（比溶剂的共额碱更强的碱不以较高浓度存在拉平效应限定了在一个特定的溶剂中所能测定的酸或碱的强度：Relativestrengthsofacidsn theconjugateacid ofa cannot be在此溶剂中不能测定he solvent（比溶剂共额酸更强的酸的相对强

8、Relativestrengthsofbasesn theconjugatebaseofa cannot be在此溶剂中不能测定he solvent（比溶剂共额碱更强的碱的相对强HSO3F, HSO3F-SbF5, HF-Acids of the extremely non-nucleophilic and non-coordinatinganionsBFHSO3F, HSO3F-SbF5, HF-Acids of the extremely non-nucleophilic and non-coordinatinganionsBF4 ,PF6 ,AsF6 andSbF6-eA.DonaldP

9、.andKatherineB.LokerDistinguishedanicSyntheticandiversityofanicProfessorOlahsresearchspansawiderangeofsyntheticandchemistry.Butmostnotably,hisworkonthechemistryofcarbocationsearnedhimthe 1994 Nobel Prize in Chemistry “for his contribution on carbocation chemistry”.SO2ClF, -78 HH H HCH3+NJC,1997,21,N

10、JC,1997,21,-HHSuperelectrophiles produced by Superelectrophiles produced by super Inwater andDMSO酸性Inwater andDMSO酸性相Inwater:HCNisHCNInisThepKa isusually largeranic npKa areanic pKaValuesforVariousAcidsinpKaValuesforVariousAcidsinWaterpKa (waterpKa Picricacid 当共轭碱的负电荷高度离域时，溶剂化效应就相对不重要。F.C.Bordwell,E

11、qulibriumaciditiesinDMSOsolution,Acc.Chem.Res. 1988, 21, 456.pKa ShiftspKa ShiftsatEnzymeActive环静电作用溶剂极性PredictingAcidStrengthinAciditiesinPredictingAcidStrengthinAciditiesinF.G.DMSO- K+ as base. DMSOhasapKa of the limiting pKa of about 33.DMSO with high dielectricconstant(=47), ion5.4.2 TwoGuidingP

12、rinciplesforPredictingRelative+ 5.4.2 TwoGuidingPrinciplesforPredictingRelative+ A+When acids being compared are neutral (HA) and creates negative conjugatebases(A-),itismostconvenienttopredicttherelativeaciditiesby examining the relative stabilities of the anionic conjugate bases. The acid with the

13、 most stable conjugate base (A-) will be the strongest acid.+ A+When the acids being compared are cationic (AH+) and create neutral conjugatebases(A),itisoftenmostconvenienttopredictrelativesacidities by examining the relative stabilities of the acids themselves. The acid HA+tismoststablewillbethewe

14、akest比较离子酸或碱的稳定性FactorsaffectingtheacidstrengthFactorsaffectingtheacidstrengthinInductive effectic5.4.3 ElectronegativityandTable5.5 pKa Values5.4.3 ElectronegativityandTable5.5 pKa Values(orRanges)ofManyDifferentKindsofAcids(R=AlkyloricHInductiveic effectSolvation rowcompoundsandmineral18-1to42R3CH

15、(simple50-9(pKa1),1.92-2.127.2112.67B.Aceticacid-Table5.5 pKa Values(orRanges)ofManyDifferentTable5.5 pKa Values(orRanges)ofManyDifferentKindsofAcids(R=AlkylorC.BenzoicacidD.Phenolp-p-2,4-PicricE.ThiolsandrelatedInductiveic effectSolvation AciditiesofCarbonHHtriptycene AciditiesofCarbonHHtriptycene

16、InductiveeffectandconjugativeHHHHH HHSaturationeffect,delocalization, stericinhibitionofHHHHHHHHHH HHSaturationeffect,delocalization, stericinhibitionofHHHHH19.5-Streitwieser, A. Jr.;Nebenzahl, L. L. .Chem.1978, 43, 7Table5.5 pKa Values(orRanges)ofManyDifferentKindsofAcids(R=AlkylorTable5.5 pKa Valu

17、es(orRanges)ofManyDifferentKindsofAcids(R=AlkylorF. Hybridization effects on I.SolvationeffectsoncarboxylicHCO 2HG.HybridizationeffectsonMeCH CH Me CCO 32H.SolvationeffectsonInductiveic effectSolvation Gas-phaseacidities(Hi)ofwaterandsimpleHi(gas) (kcalmol-1)(kJmol-most373.3374.1376.1379.2390.8least

18、Hirefers to thereaction: ROH RO- + Table5.6 pKa ValuesofCarbonA.Carbonyl8C.CyanoCH Table5.6 pKa ValuesofCarbonA.Carbonyl8C.CyanoCH 311.2 (CH Cl MeCOCH 23-39e)SO 221-9-CH B.NitroCH NTable5.6 pKa ValuesofCarbonF. PhenylTable5.6 pKa ValuesofCarbonF. PhenylH. Hybridization EG.YlidesandicPh P+-33I. Aroma

19、ticity 1,2,3-维生素AciditiesofCarbonTable3.9(insolution):TheeffectofAciditiesofCarbonTable3.9(insolution):Theeffectofthe change in hybridization of the orbital. Inductiveeffectandconjugative Acidities of carbon acids containing electron-withdrawing pKain40Acidities of carbon acids containing electron-w

20、ithdrawing pKain400Inductive effect Saturation effectCompetitiveresonance.OOCompetitiveresonance.OOTable5.7 pKa ValuesofCationicHeteroatomA.VariouseffectsonNacids,hybridization,stericsand1,8-lene-Table5.7 pKa ValuesofCationicHeteroatomA.VariouseffectsonNacids,hybridization,stericsand1,8-lene-MeNH3Im

21、idazole-+4MeNH3 + RN+ +HRN NR氮杂化轨道s组分降低引起的酸性降低StericStericEffectsonIonizationConstantsofCarboxylicStericStericEffectsonIonizationConstantsofCarboxylicsolvation: pKa -NewJ. Chem.2001,25,StericpKa -NewJ. Chem.2001,25,Stericinhibitionof NNNNN位阻效应NH H H NEt2pKa = pKa = NN H NEt2pKa = pKa = NNNpKa =pKa =

22、 ProtonAcidsandBasesofVB1焦磷酸酯离磷酸吡哆醛AcidsandBasesofVB1焦磷酸酯离磷酸吡哆醛O P ONpyridoxal 正H2N CHC OHH2N CHC OH C C O谷氨天冬氨H2N CHC H2N CHC H2N CHC C NH2组氨赖氨精氨thiamine O PO P pKa = DNA双螺旋三螺旋结构NONOOONHNH胞啶NOprotonatedHN pH= 5-NNODNA双螺旋三螺旋结构NONOOONHNH胞啶NOprotonatedHN pH= 5-NNO胞啶Watson-Crickbase嘧嘧pKa =pKa =增强生物分子酸碱

23、性段增强生物分子酸碱性段氢金属配位作用赖氨酸，pKa 酶的作用：提高酸性扁桃酸消旋酶，pKa AShiftoftheAcidityofanN-HBondinWaterDuetothe Proximity of an Ammonium or Metal Cation.OOHHONN1N1AShiftoftheAcidityofanN-HBondinWaterDuetothe Proximity of an Ammonium or Metal Cation.OOHHONN1N1NHNONON1NHHONNHHNNNNHHHHE.Kimura,JACS1997,119,RalphG.Pearson(

24、1963):ndsoftness(J.Am.Chem. Soc. 1963,85,RalphG.Pearson(1963):ndsoftness(J.Am.Chem. Soc. 1963,85,LewisA-LewisA+Hard(Lewis)acidsprefertobindtohard(Lewis)bases Soft (Lewis) acids prefer to bind to soft (Lewis) basesHardacids arecharacterizedbysmallacceptorveouter itive electronnoteasilyexcitedtbearSof

25、tacidshaveacceptoratomsoflower, with easily excited outer electrons.itvecharge,largesize,Hard bases contain highly electronegative donor atomes of low polarizability,aretypicallydifficulttooxidize,andhavenoempty low-energy orbitals available.Softbasesarepolarizable,haveectroegativedonoratoms,haveemp

26、tyortitalsoflowenergyandelctron removed by oxidizing agents.tare more Klopmans In1968,G. fiedPearsonsHSABKlopmans In1968,G. fiedPearsonsHSABprincipleusingmolecularorbital (FMO)heformofamathematicalKlopmanHardLewisacidsbindtohardLewisbasestogivecharge-controlled (ionic) complexesSoftLewisacidsbindtos

27、oftLewisbasestogiveFMO-controlled (covalent) complexesKlopman,G. J.Am.Chem.Soc. 1968,90,TheoryofLewis(HSAB)(Klopman,G.J.Am.Chem.Soc.1968,90,Soft HardSoft Hard Hardacidhardbase: SoftTheoryofLewis(HSAB)(Klopman,G.J.Am.Chem.Soc.1968,90,Soft HardSoft Hard Hardacidhardbase: SoftacidsoftCombiningPearsonsa

28、ndKlopmansHardLewisAtomicCombiningPearsonsandKlopmansHardLewisAtomiccentersofsmallionicitiveSpeciesdonotcontain electronLowelectronLikelytobestronglyHighenergy SoftLewisLargeheirsLoworpartialitiveElectronheirsEasyto polarizeandLowenergyLUMOs,but largemagnitudeLUMO PearsonsHardLewisPearsonsHardLewisA

29、cids(fromtheChemicalPearsons Borderline Lewis PearsonsSoftLewisPearsonsHard LewisPearsonsHard LewisBases(fromTheChemicalPearsonsBorderlineLewisPearsonsSoftLewisTheHSAB PrincipleanicForouresmaingroupanicTheHSAB PrincipleanicForouresmaingroupanicreactionchemistrytheapproachisverysfulwhencomparingpairsof* SodiumionNa+ isnthesilverionAlkoxideions,RO,areCopper(II)ion,Cu2+,isnthioanions,ncopper(I)ion,*Thenitrogenanionendoftheambiden