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 Each bondarisesfromtheoverlapofanH1sorbitalwithoneoftheO2porbitals Thismodelsuggeststhatthebondangleshouldbe90 whichissignificantlydifferentfromtheexperimentalvalue Pureporbitals Whydoatomicorbitalneedhybridization 为什么要杂化 LinusPauling Hybridization 1931 SimplifiedMOdiagramofdiatomicmolecules分子轨道理论 Energy 2s 2s 1 g 1 u 2p 2p 2 g 2 u 1 u 1 g 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 IfwebeginwithnAO s wemustendupwithnorbitalsafterhybridization n个原子轨道杂化得到n个杂化轨道Allnhybridsareequivalentexceptfordirectionality sameenergy 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 1s bondsoriented180 fromeachother Onesandtwop pxandpy AO smixtoformasetofthreehybridorbitals 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 Onesand3pAO smixtoformasetoffourhybridsp3orbitals sp3hybrides tetrahedral sp3杂化 四面体 CH4 Thisgivesfoursp3orbitalsthatareorientedinatetrahedralfashion Theoverlapofthesp3hybridorbitalsonCwiththe1sorbitalsontheHatomsgivesfourC H sp3 1s bondsoriented109 5 fromeachother 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 2p bonds90 fromeachotherthatareequivalent 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 TheoverlapsofthesphybridorbitalsonCwiththetwo2porbitalsonOgivethetwo bondsanditistheoverlapsofthe 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 Delocalized bond离域 键 Conditionsthatfavortheformationofdelocalized bondi Theatomsarecoplanar witheveryatomcontributingap orbitalorientatedinthesamedirection 原子共平面 每个原子提供一个同取向的p轨道ii Thenumberof electronsislessthantwicethenumberoftheparticipatingp orbitals 电子数小于轨道数2被 n orbitalnumbers m electronnumbers n 2 Delocalized bond 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 17 19valenceelectron 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 3sp2