高等有机化学PPT.ppt

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1、Advanced Organic Chemistry:Structure and Mechanisms(Part B),5th Edition，2007，By Francis A.Carey。高等有机化学基础(面向21世纪课程教材)，荣国斌,华东理工大学出版社，化学工业出版社，第3版，出版日期：2009年05月。高等有机化学反应、机理与结构（原著第五版 修订），美史密斯（Smith M.B）马奇（March J），化学工业出版社,Lewis StructuresResonanceHybrid orbitalsAromaticityFunctional Groups,Part 1:THE COV

2、ALENT BOND,Lewis structure:the electron-pair bondThe Lewis structural formula can serve as a convenient starting point to understanding the valence-bond theory of molecular structure.,The ionic bonding force arises from the electrostatic attraction between ions of opposite charge.The covalent bondin

3、g force arises from sharing of electron pairs between atoms.,I.Lewis Structures,Ionic,covalent,and polar bonds,ionic bonds:transfer of electrons,covalent bonds:sharing of electrons,electro negativity,:relative attraction for electrons in a bond-increases going up and to the right in the periodic tab

4、le,The valence-shell occupancy must not exceed 2 for hydrogen and must not exceed 8 for atoms of the first row of the periodic table.For elements of the second and later rows,the valence-shell occupancy may exceed 8.SF6,H2SO4,The heat of hydrogenation of benzene is less exothermic by about 21 kcal m

5、ol-1(88kj mol-1)than one would have expected from Lewis structure 1 on the basis of known properties of single and double bonds.,Resonance structuresThe superposition of two or more Lewis structures with different electron distributions but identical nuclear positions into a composite picture is cal

6、led resonance.,neither of these accurately describes the formate ionactual species is an average of the two(resonance hybrid),delocalizedelectrons,I.Lewis Structures,Resonance structures,more stablemajor contributor,less stableminor contributor,Draw resonance structures for the following species.If

7、the structures are not equivalent,indicate which would be the major contributor.CH3NO2CH2CHO,Resonance and tautomerism,Resonance and tautomerism,Resonance and tautomerism,Tautomerism and H-bond,cellulose,Protein and H-bond,氢键是指在氢原子与电负性很大的原子X 以共价键相结合时，同另外一个具有孤对电子对的原子Y 形成的一个弱的键，是一种由氢原子参加成键的特殊的化学键。，如下式

8、中虚线所示：AHB其中A，B 是氧、氮或氟等电负性大且原子半径比较小的原子。,Tautomerism and H-bond,原子A 到B 的距离。比范德华半径之和要小，但比共价半径之和大很多。例如甲酸分子之间的氢键，两个氧原子之间的距离为O.267nm，而范德华半径之和约为0.35nm共价半径之和为0162nm。单体甲酸分子中的OH 键长为0.098nm，其二聚体的OH 键长为0.104nm，OHO 键长为0.267nm，因此形成氢键以后OH 键长发生了变化，HO 键的键长为O.163nm，要长于O 一H 键的键长。,氢键的键长,常见氢键类型：850kJmol-1,Resonance and

9、tautomerism,Resonance and tautomerism,tautomerism,Tetrahedron Letters 41(2000)12971301,Tautomerism and reactivity,Example:,丙环唑、噁醚唑异构体均在缩合反应过程中产生，主要是由于1，2，4三唑在碱性条件下容易转化为1，3，4三唑造成的。,question:?,在 以三唑类杀菌剂为主要生产产品的化工企业，1、2、4-三氮唑的质量关乎几乎所有三唑类杀菌剂的质量，关乎企业生产效益和市场竞争力。1、2、4-三氮唑合成中异构体的分离技术显得尤为重要。有限公司预计投资70万用于1、2、

10、4-三氮唑中异构分离技术的改进，提高1、2、4-三氮唑含量，主要是控制其中异构体1、3、4-三氮唑的含量。在保证1、2、4-三氮唑生产成本不影响最终三唑类的杀菌剂成本的前提下，对1、2、4-三氮唑合成技术进行优化，对分离提纯技术进行改进,设计一条可以工业化的合理的小试路线。,Tautomer and resonance:more subtle cases,Crystalline omeprazole exists as solid solutions of twotautomers in a continuous composition range,and this raisesquestio

11、ns pertaining to the definition of the term polymorph.We obtained single crystals of five different forms ofomeprazole,with the 1:2 ratio varying from 0:100 to 15:85,Tautomeric polymorphism in omeprazole，Prashant M.Bhatt Gautam R.Desiraju，Chem.Commun.,2007,20572059,The crystal structure consists of

12、alternatelayers of molecules,first with the NH moiety anti to the aromaticring(2a)and the next with the NH syn to the ring(2b).(1:1),Diiminoisoindoline:tautomerism,conformations,and polymorphism,C h e m.C o m m u n.,2 0 0 4,8 8 6 8 8 7,Zhi-Qin Zhang,Jeffrey M.Njus,Daniel J.Sandman,Chengyun Guo,Bruce

13、 M.Foxman,PeterErk,Richard van Gelder.,only with the NH syn to the ring,Diiminoisoindoline:tautomerism,conformations,and polymorphism,C h e m.C o m m u n.,2 0 0 4,8 8 6 8 8 7,Zhi-Qin Zhang,Jeffrey M.Njus,Daniel J.Sandman,Chengyun Guo,Bruce M.Foxman,Peter Erk,Richard van Gelder.,Colors in“ROY”,Differ

14、ences in color can be accounted for from differences in conformation,5-Methyl-2-(2-nitro-phenylamino)-thiophene-3-carbonitrile,共轭分子,染料光敏剂是纳米晶体太阳能电池的关键部分。作为光敏剂，不但要求其对太阳光具有良好的,This compound exhibits an intense red-shifted absorption spectrum(max)1417 nm;)1.2 105 M-1 cm-1)and a small electrochemical HO

15、MO-LUMO gap(0.61 eV).The crystal structure shows that it forms-stacked dimers with a short Ni Ni distance(3.32).,A Porphyrin Fused to Four AnthracenesJ Am Chem Soc.2011;133(1):30-1.Nicola K.S.Davis,Amber L.Thompson,and Harry L.Anderson,III.Valence Bond Model,A.Atomic and molecular orbitals,H+H HH,Tw

16、o electrons in s1s are lower energy than in the separate atoms covalent bond,Shape and Orientation,The electron distribution must have thecharacteristics of both s(spherical)and p(node)orbitals.The four new electron distributions(orbitals)will orient as far away from eachother as possible.Toward the

17、 corners of atetrahedron.,III.Valence Bond Model,B.Hybrid atomic orbitals,1.sp3 hybridization,CH4 facts:,tetrahedral,4 equivalent bonds,III.Valence Bond Model,Hybrid atomic orbitals,1.sp3 hybridization,III.Valence Bond Model,B.Hybrid atomic orbitals,2.sp2 hybridization,C2H4 facts:,all six atoms liei

18、n same plane,trigonal planar=sp2,III.Valence Bond Model,B.Hybrid atomic orbitals,2.sp2 hybridization,III.Valence Bond Model,B.Hybrid atomic orbitals,3.sp hybridization,C2H2 facts:,linear=sp,III.Valence Bond Model,B.Hybrid atomic orbitals,3.sp hybridization,III.Valence Bond Model,B.Hybrid atomic orbi

19、tals,What is the hybridization of each indicated atom in the following compound?,17-ethynylestradiol(“The Pill”),IV.Functional Groups,Atoms or groups of atoms that behave similarly,regardless of the structure to which they are attached.,methanol,ethanol,b-phenethyl alcohol(lilacs),geraniol,retinol(v

20、it A),IV.Functional Groups,Hydrocarbons(C&H only),Heteroatomic compounds,aliphatic,aromatic,alkanes,alkenes,alkynes,cyclic compounds,alcohols,ethers,aldehydes,ketones,carboxylic acids,esters,amines,amides,In the allyl system each carbon is trigonal,and each uses sp2 hybrids to make bonds to its neig

21、hbors.,Delocalized bonding,Resonance and Aromaticity1.Benzene is much less reactive toward electrophiles,such as halogens,than are simple alkenes,and when it reacts it gives substitution rather than addition.,2.NMR of benzene and its derivatives shows the protons bonded to the ring to be experiencin

22、g a stronger effective magnetic field than do protons attached to simple alkenes.,3.The heat of hydrogenation of benzene is less exothermic by about 21 kcal mol-1(88kj mol-1)than one would have expected from Lewis structure 1 on the basis of known properties of single and double bonds.,AROMATICITY,A

23、romatic compounds are cyclic unsaturated molecules characterized by certain magnetic effects and by substantially different chemical reactivity and greater thermodynamic stability than would be expected from a noncyclic model.Antiaromatic compounds are cyclic unsaturated compounds that are thermodyn

24、amically less stable than would be expected from a noncyclic model.,Capable of existence only when immobilized by freezing in an inert matrix at very low temperature.Though a stable compd.,does not have a planar ring,The simple resonance theory fails to explain the contrast between the properties of

25、 benzene on the one hand and of cyclobutadiene and cyclooctatetraene on the other,but we may turn to molecular orbitals for the solution.,Huckel theory:any regular plane polygon conjugated ring,If the number of pairs is even(4n),the last pair will be the only occupants of a doubly degenerate level a

26、nd so one electron will go into each orbital with spins parallel.It is found that the 4n+2 rings are stabilized compared with the openchain analog,whereas the 4n systems are destabilized.,Theory thus explains the classification of cyclic conjugated systems as aromatic or antiaromatic according to th

27、e energy criterion,which we may define as follows:a molecule is aromatic if it is thermodynamically more stable than expected for the open-chain analog,and it is antiaromatic if it is thermodynamically less stable.A compound showing neither stabilization nor destabilization would be classed as nonar

28、omatic.,Theory suggests that an applied magnetic field perpendicular to a conjugated ring that has 4n+2 electrons will cause the electrons to behave as though they were circulating around the ring and generating their own small magnetic field.This circulation is called the ring current.,Homoaromatic

29、ity,They are systems in which the systems is interrupted at one or more points by a saturated center but in which geometry still permits significant overlap of the p orbitals across the insulating gap.,同芳体系是指被一个或两个Csp3隔开的环状体系，其分子的几何 形状允许P轨道超越间隔间隙进行有效重叠，且电子数符合4n+2规则而具有芳香性。因此产生芳香性的结构，叫同芳结构。此结构可由NMR证明。

30、,（一）反芳结构 分子因电子离域而更不稳定。由于电子离域而相当大地提高了能量的分子体系，叫反芳体系。离域的电子数为4n。实验判断：NMR显示出该体系具有顺磁环电流。环外质子向高磁场移动。反芳体系很少存在，因一切分子总趋于使本身能量更低。,Tautomer and aromaticity,Tautomer and aromaticity,Tautomer and aromaticity,Tautomer and aromaticity,Homoconjugation?,intramolecular,Homoconjugation:spiroconjugation effect,Homoconju

31、gation:spiroconjugation effect,有机分子中电子空间作用的多样性,螺共轭效应及其应用,魏荣宝,张大为,刘 博,刘 洋,李文丽,贾辰熙,有 机 化 学,Vol.29(4),2009,517527.,前线轨道理论,HOMO(highest occupied molecular orbital):指被电子占据的能量最高的轨道LUMO(Lowest unoccupied molecular orbital)：指未被电子占据的能量最低的空轨道热反应为基态反应；光反应为激发态反应。单分子反应只涉及分子的HOMO；双分子反应涉及一个分子的HOMO和另一个分子的LUMO。,前线轨道

32、理论,前线轨道理论,Interactions between molecules,HOMO-LUMO InteractionsThe strongest interactions will be between those orbitals that are close to each other in energy.The significant interactions are between filled orbitals of one molecule and empty orbitals of the other.The most important interactions are between HOMO of one molecule and the LUMO of the other.,前线轨道理论,下列化合物是否具有芳香性，其HNMR有何特征？,