化学竞赛杂化轨道理论课件

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,18.1 Theory of hybrid orbital,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,bond arises from the overlap of an H1,s,orbital with one of the O2,p,orbitals. This model suggests that the bond angle should be 90, which is significantly different from the experimental value.,104.5,C,2v,O,H,H,2s,2p,Pure p orbitals,2s,2p,O,2H,H,2,O,O,H,H,Why do atomic orbital need hybridization?,为什么要杂化？,sp,3,2s,2p,O,2H,O,*,sp,3,Linus Pauling,Hybridization (1931),Simplified MO diagram of diatomic molecules,分子轨道理论,Energy,2s,2s,1,g,1,u,2p,2p,2,g,2,u,1,u,1,g,p,z,HOMO,LUMO,N,2,:,KK(3),2,(4),2,(1),4,(5),2,Hybridization of 2s and 2p 2s,和,2p,的杂化,Boundary surfaces of,(a) 2s+2p,(b) 2s-2p,Energy diagram for X,2,: (a) with hybridization and (b) without 2s-2p,z,hybridization. The 1s orbitals are left out.,(a),(b),2. Construction of hybrid orbitals,杂化轨道的构造,If we begin with,n,AOs, we must end up with,n,orbitals after hybridization.,n,个原子轨道杂化得到,n,个杂化轨道,All,n,hybrids are equivalent except for directionality, same energy.,所有的杂化轨道能级相同，但方向不同,a. sp hybridization (linear species) sp,杂化，直线型,One s and one p AO mix to form a set of two hybrid orbitals.,sp,=180, linear,Normalization and orthogonality,1s,1s,2 H,Hybridization,The promotion energy can be considered a part of the energy required to form hybrid orbitals.,The overlap of the hybrid orbitals on Be with the 1s orbitals on the H atoms gives two Be-H (sp)-1s,bonds oriented 180from each other.,Be* (sp),2s,2p,Be,Be*,BeH,2,sp,2p,One s and two p (p,x,and p,y,) AOs mix to form a set of three hybrid orbitals.,b. sp,2,hybridization (trigonal planar),sp,2,杂化，平面三角形,sp,2, D,3h,=120, triangular,f=1.991,， ,=1/3,h1,h2,h3,x,y,A trigonal planar molecule and sp,2,hybridization: the bonding in BH,3,2s,2p,B,B*,BH,3,sp,2,hybrid,p,orbital,1s,1s,1s,3 H,B*,sp,2,2p,h1,h2,h4,h3,z,One s and 3 p AOs mix to form a set of four hybrid sp,3,orbitals.,sp,3,hybrides (tetrahedral),sp,3,杂化，四面体,CH,4,2s,2p,1s,1s,1s,1s,C,4 H,C*,sp,3,C* (sp,3,),This gives four sp,3,orbitals that are oriented in a tetrahedral fashion. The overlap of the sp,3,hybrid orbitals on C with the 1s orbitals on the H atoms gives four C-H (sp,3,)-1s,bonds oriented 109.5 from each other.,h1,h2,x,y,h3,h4,h5,z,dsp,3,(sp,3,d) hybrides (trigonal bipyramidal),dsp,3,(sp,3,d),杂化，三角双锥,The bond lengths will not be the same because there is more d contribution to the axial hybrid orbitals.,h1,h2,x,y,h3,h4,h5,z,The bond lengths will not be the same because there is more d contribution to the axial hybrid orbitals.,平面和轴向轨道是不等价的。,In the case dsp,3, the axial bond length is shorter,While it is longer in the case sp,3,d,（,dsp,3,杂化,轴向键长较短，,sp,3,d,杂化则较长,PF,5,3s,3p,P,P*,3d,P* (,sp,3,d),3d,We need hybrid orbitals suitable for bonds to 5 atoms.,n,s and,n,p combinations can only provide four, so we need to use,n,d orbitals,(if they are available),.,3d,z,2,3p,z,3p,y,3p,x,3s,sp,3,d,z,2,The appropriate mixture to form a trigonal bipyramidal arrangement of hybrids involves all the,n,s and,n,p orbitals as well as the,n,d,z,2,orbital.,Valence bond theory treatment of a trigonal bipyramidal molecule: the bonding in PF,5,F,2s,2p,F,2s,2p,F,2s,2p,3d,P* (,sp,3,d),F,2s,2p,F,2s,2p,The overlap of the sp,3,d hybrid orbitals on P with the 2p orbitals on the F atoms gives five P-F (sp,3,d)-2p,bonds in two sets: the two,axial,bonds along the z-axis (180 from each other) and three,equatorial,bonds in the xy plane (120 from each other and 90 from each axial bond).,This means that the 5 bonds are not equivalent!,Square planar: D,4h,h,1,x,y,h3,h,2,h4,Eg. Ni(CN),4,2-,dsp,2,hybrides (square planar),dsp,2,杂化，平面四边形,5,1,2,3,4,6,x,y,z,d,2,sp,3,(sp,3,d,2,) hybrides (Octahedral),d,2,sp,3,(sp,3,d,2,),杂化，八面体,SF,6,The overlap of the sp,3,d,2,hybrid orbitals on S with the 2p orbitals on the F atoms gives six S-F (sp,3,d,2,)-2p,bonds 90 from each other,that are equivalent,.,You can figure out the normalization coefficients.,3d,z,2,3p,z,3p,y,3p,x,3s,sp,3,d,2,3d,x,2,-y,2,3s,3p,S,S*,3d,S* (,sp,3,d,2,),3d,F,F,F,F,F,F,Hybridization schemes,sp,n,d,m,gives a “complete” set of hybrid orbitals for “any” geometry.,sp,Linear,直线,sp,2,Trigonal planar,平面三角形,sp,3,Tetrahedral,四面体,sp,3,d (d,z,2,),Trigonal bipyramidal,三角双锥,sp,3,d(d,x,2,-,y,2,),square-based pyramidal,四方锥,sp,3,d,2,Octahedral,八面体,sp,2,d,Square planar,平面四边形,Valence bond theory treatment of,p,-bonding,p,-,键的价键理论处理,sp,2p,C*(sp),O,2s,2p,O,2s,2p,2s,2p,C,The overlaps of the sp,hybrid orbitals on C with the two 2p orbitals on O give the two,bonds and it is the overlaps of the “left over” p orbitals on C with the appropriate p orbitals on O that form the (2p-2p),p,bonds between each two atoms.,O,C,O,Valence bond theory treatment of,p,-bonding: the bonding in ethene,There are three “objects” around each C so the geometry is trigonal planar at each carbon. The shape is given by AX,3,for each carbon.,2s,2p,Each C,sp,2,2p,C*(sp,2,),1s,1s,1s,1s,4 H,sp,2,2p,C*(sp,2,),Each C*,The overlap of the sp,2,hybrid orbitals on C with the the 1s orbitals on each H give the four terminal (sp,2,-1s),bonds. The double bond between the C atoms is formed by a (sp,2,- sp,2,),bond and the (2p-2p),p,bond.,Valence bond theory treatment of,p,-bonding: the bonding in the nitrate anion,There are three “objects” around N so the geometry is trigonal planar. The shape is given by AX,3,(trigonal planar).,2s,2p,N,N,+,O,-,2s,2p,O,-,2s,2p,O,2s,2p,sp,2,2p,N,+,*(sp,2,),The overlap of the sp,2,hybrid orbitals on N with the the 2p orbitals on the O give the three (sp,2,-2p),bonds and it is the overlap of the “left over” p orbital on N with the appropriate orbital on the uncharged O atom that forms the (2p-2p),p,bond.,N,N,价键理论 共振结构,VBT gives only one of the canonical structures at a time.,分子轨道理论离域,p,键,MO gives delocalized,p,-orbital,C,6,H,6,(benzene),-bonds,Each C uses sp,2,orbitals to form 3,-bonds,1 p orbital on each C remains,价键理论共振结构,C,6,H,6,(benzene) delocalized,p,-bonds,分子轨道理论离域,p,键,s,frame work,p,resonance,Delocalized, bond,离域,键,Conditions that favor the formation of delocalized,bond,i. The atoms are coplanar, with every atom contributing a p-orbital orientated in the same direction.,原子共平面，每个原子提供一个同取向的,p,轨道,ii. The number of, electrons is less than twice the number of the participating p-orbitals. ,电子数小于轨道数,2,被,n-orbital numbers, m-electron numbers (n2),Delocalized, bond,Phenolphthalein is an organic compound (C,20,H,14,O,4,) used as an,acid-base indicator,. The compound is,colorless in acidic,solution and,pinkish in basic,solution (with the transition occuring around pH 9).,酚酞变色原因,sp,2p,C*(sp),O,2s,2p,O,2s,2p,2s,2p,C,O,C,O,18.2 Structure of ABn Molecules,（,Ab,n,分子的结构）,1. AB,2,valence electron 6 + 7x2 = 20,H,2,O, H,2,S,valence electron 8,i. Non linear type(bent) (20 valence electron),ex.,OF,2, OCl,2, SCl,2, TeBr,2,O: sp,3,hybridization,ii. Non linear type(bent) (1719 valence electron),ex. 18 O,3,(valence electron),O: sp,2,hybridization + p,z,O,O,O,.,.,.,p,z,sp,2,orbital,p,z,p,z,anti-bonding,non-bonding,bonding,Isoelectron analogy: SO,2,17 valence electron NO,2,19 valence electron ClO,2,.,.,iii. Linear type (AB,2,16 valence electron),CO,2,C: sp hybridization +p,x,+p,y,Isoelectron analogy : CO,2, NO,2,+, N,2,O, N,3,-, COS, BeCl,2, HgCl,2,iv. Linear type (AB,2,22 valence electron),ICl,2,-,XeF,2,sp,3,d hybridization,18.2 Structure of ABn Molecules,2. AB,3,i. Trigonal Pyramidal type (8, or 26 valence electron),ex.,NH,3, PF,3, PCl,3, AsCl,3,sp,3,hybridization,ii. Trigonal planar type (6, 24 valence electron),Centric atom B: sp,2,hybridization,24,-6,18,-12,6,Isoelectron analogy: AlF,3, NO,3,-, CO,3,2-, SO,3, Cl,2,CO,(H,2,N),2,C=O, Cl,2,C=S,anti-bonding,non-bonding,bonding,For four atom angular type moleculars, forming one bonding, two nonbonding and one antibonding orbitals, in general,Example: BH,3,ex. BF,3, NO,3,-, CO,3,2-,SO,3,sp,2,3 sp,2,hybrid orbitals each with one electron.,This one electron pairs with the hydrogen electron.,ii. Trigonal planar type (6, 24 valence electron),ex. ClF,3, BrF,3,sp,3,d,hybrid orbitals,iii. T type (28 valence electron),18.2 Structure of ABn Molecules,3. AB,4,Tetragonal Pyramidal type,ex.,CH,4, NH,4,+, CCl,3,sp,3,hybridization,dp-, bond,ex.,PO,4,3-, SO,4,2-,d,xz,p,z,x,x,p,x,