化学竞赛杂化轨道理论.ppt

18.1Theoryofhybridorbital杂化轨道理论,分子轨道理论价键理论,化学键理论,价电子离域,价电子定域在两原子之间或成为孤对电子,每个原子提供一个价电子和一个轨道重叠成键,EachbondarisesfromtheoverlapofanH1sorbitalwithoneoftheO2porbitals.Thismodelsuggeststhatthebondangleshouldbe90,whichissignificantlydifferentfromtheexperimentalvalue.,Pureporbitals,Whydoatomicorbitalneedhybridization?为什么要杂化？,LinusPauling,Hybridization(1931),SimplifiedMOdiagramofdiatomicmolecules分子轨道理论,Energy,2s,2s,1g,1u,2p,2p,2g,2u,1u,1g,pz,HOMO,LUMO,N2:KK(3)2(4)2(1)4(5)2,Hybridizationof2sand2p2s和2p的杂化,Boundarysurfacesof(a)2s+2p(b)2s-2p,EnergydiagramforX2:(a)withhybridizationand(b)without2s-2pzhybridization.The1sorbitalsareleftout.,(a),(b),2.Constructionofhybridorbitals杂化轨道的构造,IfwebeginwithnAOs,wemustendupwithnorbitalsafterhybridization.n个原子轨道杂化得到n个杂化轨道Allnhybridsareequivalentexceptfordirectionalitysameenergy.所有的杂化轨道能级相同，但方向不同,a.sphybridization(linearspecies)sp杂化，直线型,OnesandonepAOmixtoformasetoftwohybridorbitals.,sp,=180,linear,Normalizationandorthogonality,Hybridization,Thepromotionenergycanbeconsideredapartoftheenergyrequiredtoformhybridorbitals.,TheoverlapofthehybridorbitalsonBewiththe1sorbitalsontheHatomsgivestwoBe-H(sp)-1sbondsoriented180fromeachother.,Onesandtwop(pxandpy)AOsmixtoformasetofthreehybridorbitals.,b.sp2hybridization(trigonalplanar)sp2杂化，平面三角形,sp2,D3h,=120,triangular,f=1.991，=1/3,Atrigonalplanarmoleculeandsp2hybridization:thebondinginBH3,BH3,sp2hybrid,porbital,h1,h2,h4,h3,z,Onesand3pAOsmixtoformasetoffourhybridsp3orbitals.,sp3hybrides(tetrahedral)sp3杂化，四面体,CH4,Thisgivesfoursp3orbitalsthatareorientedinatetrahedralfashion.Theoverlapofthesp3hybridorbitalsonCwiththe1sorbitalsontheHatomsgivesfourC-H(sp3)-1sbondsoriented109.5fromeachother.,x,y,h4,h5,z,dsp3(sp3d)hybrides(trigonalbipyramidal)dsp3(sp3d)杂化，三角双锥,Thebondlengthswillnotbethesamebecausethereismoredcontributiontotheaxialhybridorbitals.,x,y,h4,h5,z,Thebondlengthswillnotbethesamebecausethereismoredcontributiontotheaxialhybridorbitals.平面和轴向轨道是不等价的。,Inthecasedsp3,theaxialbondlengthisshorter,Whileitislongerinthecasesp3d（dsp3杂化轴向键长较短，sp3d杂化则较长,PF5,Valencebondtheorytreatmentofatrigonalbipyramidalmolecule:thebondinginPF5,Squareplanar:D4h,h1,x,y,h3,h2,h4,Eg.Ni(CN)42-,dsp2hybrides(squareplanar)dsp2杂化，平面四边形,5,1,2,3,4,6,x,y,z,d2sp3(sp3d2)hybrides(Octahedral)d2sp3(sp3d2)杂化，八面体,SF6,Theoverlapofthesp3d2hybridorbitalsonSwiththe2porbitalsontheFatomsgivessixS-F(sp3d2)-2pbonds90fromeachotherthatareequivalent.Youcanfigureoutthenormalizationcoefficients.,Hybridizationschemes,spndmgivesa“complete”setofhybridorbitalsfor“any”geometry.,Valencebondtheorytreatmentofp-bondingp-键的价键理论处理,sp,2p,C*(sp),O,2s,2p,O,2s,2p,2s,2p,C,TheoverlapsofthesphybridorbitalsonCwiththetwo2porbitalsonOgivethetwobondsanditistheoverlapsofthe“leftover”porbitalsonCwiththeappropriateporbitalsonOthatformthe(2p-2p)pbondsbetweeneachtwoatoms.,Valencebondtheorytreatmentofp-bonding:thebondinginethene,Therearethree“objects”aroundeachCsothegeometryistrigonalplanarateachcarbon.TheshapeisgivenbyAX3foreachcarbon.,Theoverlapofthesp2hybridorbitalsonCwiththethe1sorbitalsoneachHgivethefourterminal(sp2-1s)bonds.ThedoublebondbetweentheCatomsisformedbya(sp2-sp2)bondandthe(2p-2p)pbond.,Valencebondtheorytreatmentofp-bonding:thebondinginthenitrateanion,Therearethree“objects”aroundNsothegeometryistrigonalplanar.TheshapeisgivenbyAX3(trigonalplanar).,Theoverlapofthesp2hybridorbitalsonNwiththethe2porbitalsontheOgivethethree(sp2-2p)bondsanditistheoverlapofthe“leftover”porbitalonNwiththeappropriateorbitalontheunchargedOatomthatformsthe(2p-2p)pbond.,价键理论共振结构VBTgivesonlyoneofthecanonicalstructuresatatime.,分子轨道理论离域p键MOgivesdelocalizedp-orbital,C6H6(benzene)-bonds,EachCusessp2orbitalstoform3-bonds1porbitaloneachCremains价键理论共振结构,C6H6(benzene)delocalizedp-bonds分子轨道理论离域p键,sframework,presonance,Delocalizedbond离域键,Conditionsthatfavortheformationofdelocalizedbondi.Theatomsarecoplanar,witheveryatomcontributingap-orbitalorientatedinthesamedirection.原子共平面，每个原子提供一个同取向的p轨道ii.Thenumberofelectronsislessthantwicethenumberoftheparticipatingp-orbitals.电子数小于轨道数2被,n-orbitalnumbers,m-electronnumbers(n2),Delocalizedbond,Phenolphthaleinisanorganiccompound(C20H14O4)usedasanacid-baseindicator.Thecompoundiscolorlessinacidicsolutionandpinkishinbasicsolution(withthetransitionoccuringaroundpH9).酚酞变色原因,sp,2p,C*(sp),O,2s,2p,O,2s,2p,2s,2p,C,18.2StructureofABnMolecules（Abn分子的结构）,1.AB2,valenceelectron6+7x2=20,H2O,H2S,valenceelectron8,i.Nonlineartype(bent)(20valenceelectron)ex.OF2,OCl2,SCl2,TeBr2,O:sp3hybridization,ii.Nonlineartype(bent)(1719valenceelectron)ex.18O3(valenceelectron)O:sp2hybridization+pz,pz,sp2orbital,pz,pz,.,.,iii.Lineartype(AB216valenceelectron)CO2C:sphybridization+px+py,Isoelectronanalogy:CO2,NO2+,N2O,N3-,COS,BeCl2,HgCl2,iv.Lineartype(AB222valenceelectron)ICl2-XeF2,sp3dhybridization,18.2StructureofABnMolecules,2.AB3,i.TrigonalPyramidaltype(8,or26valenceelectron)ex.NH3,PF3,PCl3,AsCl3,sp3hybridization,ii.Trigonalplanartype(6,24valenceelectron)CentricatomB:sp2hybridization,24-618-126,Isoelectronanalogy:AlF3,NO3-,CO32-,SO3,Cl2CO,(H2N)2C=O,Cl2C=S,Forfouratomangulartypemoleculars,formingonebonding,twononbondingandoneantibondingorbitals,ingeneral,Example:BH3,ex.BF3,NO3-,CO32-,SO3,sp2,3sp2hybridorbitalseachwithoneelectron.Thisoneelectronpairswiththehydrogenelectron.,ii.Trigonalplanartype(6,24valenceelectron),ex.ClF3,BrF3,sp3dhybridorbitals,iii.Ttype(28valenceelectron),18.2StructureofABnMolecules,3.AB4,TetragonalPyramidaltypeex.CH4,NH4+,CCl3,sp3hybridization,