分子间和分子内的相互作用力.ppt

IntermolecularForces 之物质结构 3 分子间作用力 Dr XiaogaiYangDepartmentofChemicalBiologySchoolofPharmaceuticalSciencesPekingUniversityEmail yxg HowDrugworks Amajorityofpharmacologicresponsesaremediatedthroughreceptors WeakInteractionsAreCrucialtoMacromolecularStructureandFunction 云腾致雨露结为霜 IntermolecularForces Theboilingpointandmeltingpointincreasewithincreasingintermolecularforces Molecularpolarity Instantaneousdipole Permanentdipole Intermolecularforcesareelectrostaticforces TheOriginationofIntermolecularForces TypesofIntermolecularForces OrientationForce InductionForce LondonDispersionForce H Bonding Ion DipoleForces HydrophobicInteractions OrientationForce Dipole DipoleForce InductionForce Dipole InducedDipoleForce LondonDispersionForce InducedDipole InducedDipoleForce Polarizability Dispersionforcetendstoincreasewithincreasingmolecularmass Summary vanderWaalsForces 分子间作用能的分配 Exercise ExceptforvanderWaalsforces theremustbesomeotherforce 氢键 H Bonding X H Y anunsharedelectronpair Oneofthesmalleratoms X相同 Y相同 X Y均相同 AhydrogenbondisanattractiveinteractionbetweenanunsharedelectronpaironanelectronegativeO N andFandapositivelypolarizedhydrogenatombondedtoanotherO N orF highboilingpoints lowboilingpoints 分子间缔合 沸点升高 熔点升高 可形成分子间或分子内氢键Inter intra molecularhydrogenbond Awatermoleculecanformuptofourhydrogenbonds Hydrogenbondingbyawatermolecule aroundamoleculeinthesolidintheliquid StructureandPropertiesofWater BecauseofHydrogenBonding Waterhasauniquelyhighspecificheat 1cal g C andauniquelyhighheatofvaporization 541 6cal g Thermalregulationoftheclimate Absorbsheatduringtheday vaporizationofwater Warmstheearthduringthenight dewetc Thedensityofsolidwaterislessthanliquidwater Veryunusual Thisallowslifetoexistinouroceansandlakes DNA分子中存在氢键 Ion DipoleForces Interactionbetweenanion Na andadipole water Strongestofallintermolecularforces HydrophobicInteractions Thetendencyofnonpolarmoleculestoself associateinwaterdefinedashydrophobiceffect Straightflush Junk John shand Dave shand 1878年 L Boltzman提出了熵与微观状态数的关系 S klnWW thenumberofpossiblearrangementsinthesystemk Boltzmann sconstant Thedrivingforceisincreasedsolvententropy WeakInteractionsAreCrucialtoMacromolecularStructureandFunction H Bond 10 40 kJ mol Relativestrength Stronglyrepulsiveatshortinternucleardistances veryweakatlonginternucleardistances WorkingRange Veryimportantinproteinfolding resultsinagreatvarietyofproteinshapes sizes PropertiesofSolutions ColligativeProperties1 loweringtheVaporPressure2 Boiling PointElevation3 Freezing PointDepression4 Osmosis FactorsAffectingSolubility Dynamicequilibrium FactorsAffectingSolubility Thesolutionprocess Solvation Hydration 1 Solute soluteinteractions 2 Solvent solventinteractions 2 Solute solventinteractions SolutionFormation EnergyChanges SpontaneityandDisorder Processesinwhichtheenergycontentofthesystemdeceasestendtooccurspontaneously Processesinwhichthedisorderofthesystemincreasestendtooccurspontaneously NH4NO3 H 26 4kJ mol Substanceswithsimilarintermolecularattractiveforcestendtobesolubleinoneanother Likedissolveslike CH2 CH2 C OH O CH CH3 CH3 ColligativeProperties Differfromthoseofthepuresolvent Dependprimarilyontheconcentrationnotthekindofsoluteparticles Dependingonthecollection Thevaporpressureofaliquidisthepressureexertedbyitsvaporwhentheliquidandvaporstatesareindynamicequilibrium Anonvolatilesolutereducestherateofvaporizationofthesolvent Theextenttowhichanonvolatilesolutelowersthevaporpressureisproportionaltoitsconcentration Boilingpoint Liquidsboilwhentheexternalpressureequalsthevaporpressure Twowaystogetaliquidtoboil increasetemperatureordecreasepressure Normalboilingpointistheboilingpointat760mmHg 1atm BoilingpointisdependentontheintermolecularforcesPolarmoleculeshavehigherb p thannonpolarmolecules Freezingpoint Thefreezingpointcorrespondstothetemperatureatwhichthevaporpressuresofthesolidandliquidphasesarethesame TheConcentrationofSoluteParticles Nonelectrolytes Onemoleofanonelectrolyteproducesonemoleofsoluteparticlescsoluteparticles c Electrolytes ExistasionsinsolutionProvidemorethanonemoleofparticlespermoleofsolutedissolvedcs p i c iisthemolesofsoluteparticlespermolesolute 1 LoweringtheVaporPressure Dissolvedsolutelowersvaporpressureofsolvent PA APA Roault sLaw PA thevaporpressureofthesolutionXA themolefractionofthesolventPA thevaporpressureofthepuresolvent Idealsolutions Realsolutions Whenthesoluteconcentrationislowandwhenthesoluteandthesolventaremuchalikeinmolecularsizeandinthestrengthandtypeofintermolecularattractions Whatyouexpectforthevaporpressurewhentheintermolecularforcesbetweensolventandsoluteareweakerthanthosebetweensolventandsolventandbetweensoluteandsolute Conversly whatyouexpectwhentheinteractionsbetweensoluteandsolventareexceptionallystrong Boiling PointElevationAndFreezing PointDepression DTb Kbm DTf Kfm Kb molalboiling pointelevationconstant m molality thenumberofmolesofsoluteper1000gofsolvent Kf molalfreezing pointdepressionconstant 强电解质的依数性偏差 DeviationofColligativePropertiesforStrongElectrolytes 电解质稀溶液的依数性 p iK bB Tb iKb bB Tf iKf bB 难挥发的非电解质稀溶液的依数性 p K bB Tb Kb bB Tf Kf bB 对AB型强电解质 NaCl i 2A2B型 Na2SO4 或AB2型 MgCl2 强电解质 i 3 近似值 i称校正因子 Molarity M Amountofsolute inmoles Volumeofsolution inliters Molality m Amountofsolute inmoles Massofsolvent inkilograms Anantifreezesolutionispreparedcontaining40 0gofethyleneglycol molarmass 62 0g mol in60 0gwaterCalculatethefreezingandboilingpointsofthissolution Solution Forwater Kf 1 86 andKb 0 52 Hencethesolutionshouldfreezeat 20 1 andboilat105 6 4 Osmosis Diffusion MicroconCentrifugalFilterUnit 超滤膜 ultra filtrationmembrane 透析袋 dialysistubing 产生渗透条件 渗透方向 稀溶液浓溶液 渗透现象会无止境地进行下去吗 Thenetmovementofsolventisalwaystowardthemoreconcentratedsolution 渗透现象 半透膜 产生渗透原因 OsmosisPressure ThePressurerequiredtopreventosmosis PV nRTP cRT Example Calculatetheosmoticpressureof0 10mol Lglucosesolutionat25 Howabout0 10mol LNaClsolution Solution cos glucose cglucose 0 10mol LP glucose cosRT 0 10 x8 31x298 250kPacos NaCl ic 2x0 10 0 20mol LP NaCl 0 20 x8 31x298 500kPa TheunithereiskPa JacobusHenricusvan tHoff1852 1911 例 25 时 求0 9 的生理盐水的渗透压是多少 渗透浓度 Osmolarity 单位 渗透摩尔每升 Osmol L 或毫渗透摩尔每升 mOsmol 每升溶液中所能产生渗透效应的各物质质点的总浓度 正常人血浆总渗透浓度为303 7 临床规定 渗透方向 低渗高渗 Osmosisandlivingcell CellularRespondstoBodyFluidTonicity Isotonic Hypertonic Hypotonic 例 1 00gofhemeisdissolvedinwateranddilutedto100mL At20 theosmoticpressureismeasuredtobe0 366kPa Calculatethemolarmassofheme Howaboutthefreezingpointofthesolution Solution P cRT c P RT 0 366 8 81x293 1 50 x10 4mol Ln c V 1 50 x10 4x100 x10 3 1 50 x10 5molMolarmass m n 1 00 1 50 x10 5 6 67x104g molDTf Kf bB Kf c 1 50 x10 4x1 86 2 79x10 4 Hencethishemesolutionshouldfreezeat0 00 例 1 00gofhemeisdissolvedinwateranddilutedto100mL At20 theosmoticpressureismeasuredtobe0 366kPa Calculatethemolar