有机化学英文教案

有机化学英文教案内容摘要：

dividual Lewis structures are called contributing structuresconnect individual contributing structures by doubleheaded (resonance) arrowsthe molecule or ion is a hybrid of the various contributing structuresExamples: equivalent contributing structuresCurved arrow: a symbol used to show the redistribution of valence electronsIn using curved arrows, there are only two allowed types of electron redistribution:from a bond to an adjacent atomfrom an atom to an adjacent bondElectron pushing is a survival skill in organic chemistrylearn it well!All contributing structures must1. have the same number of valence electrons2. obey the rules of covalent bondingno more than 2 electrons in the valence shell of H no more than 8 electrons in the valence shell of a 2nd period element3rd period elements, such as P and S, may have up to 12 electrons in their valence shells3. differ only in distribution of valence electrons。 the position of all nuclei must be the same4. have the same number of paired and unpaired electronsfilled valence shellsstructures in which all atoms have filled valence shells contribute more than those with one or more unfilled valence shellsstructures that carry a negative charge on the more electronegative atom contribute more than those with the negative charge on the less electronegative atom Molecular Orbital TheorySigma 1s bonding and antibonding MOsMO energy diagram for H2: (a) ground state and (b) lowest excited statepi bonding and antibonding MOs Hybrid OrbitalsHybridization of orbitals (L. Pauling)the bination of two or more atomic orbitals forms a new set of atomic orbitals, called hybrid orbitalsWe deal with three types of hybrid orbitalssp3 (one s orbital + three p orbitals)sp2 (one s orbital + two p orbitals)sp (one s orbital + one p orbital)Overlap of hybrid orbitals can form two types of bonds depending on the geometry of overlaps bonds are formed by “direct” overlapp bonds are formed by “parallel” overlapeach sp3 hybrid orbital has two lobes of unequal sizethe sign of the wave function is positive in one lobe, negative in the other, and zero at the nucleusthe four sp3 hybrid orbitals are directed toward the corners of a regular tetrahedron at angles of 176。 orbital overlap pictures of methane, ammonia, and watersp2 Hybrid Orbitalsthe axes of the three sp2 hybrid orbitals lie in a plane and are directed toward the corners of an equilateral trianglethe unhybridized 2p orbital lies perpendicular to the plane of the three hybrid orbitalsBonding in Ethylenesp Hybrid Orbitalstwo lobes of unequal size at an angle of 180176。 the unhybridized 2p orbitals are perpendicular to each other and to the line created by the axes of the two sp hybrid orbitalsBonding in Acetylene, C2H2Hybrid OrbitalsChapter 2 Alkane and cycloalkane Alkane The definition of alkaneAlkanes are posed of only carbon atoms and hydrogen atoms and contain only single bonds. Compounds that contain only carbon and hydrogen are called hydrocarbons, so an alkane is a hydrocarbon that has only single bonds. Alkanes in which the carbons form a continuous chain with no branches are called straightchain alkanes. The names of several straightchain alkanes are given in Table . It is important that you learn the names of at least the first 10.The family of alkanes shown in the table is an example of a homologous series. A homologous series (homos is Greek for “the same as”) is a family of pounds in which each member differs from the next by one methylene (CH2) group. The members of a homologous series are called homologs. Propane (CH3CH2CH3) and butane (CH3CH2CH2CH3) are homologs. StructureConstitutional IsomerismConstitutional isomers: pounds with the same molecular formula but a different connectivity of their atomsexample: C4H10 Nomenclature of Alkyl SubstituentsRemoving a hydrogen from an alkane results in an alkyl substituent (or an alkyl group).Alkyl substituents are named by replacing the “ane” ending of the alkane with “yl.” The letter “R” is used to indicate any alkyl group.Primary (1176。 ) C: a carbon bonded to one other carbon1176。 H: a hydrogen bonded to a 1176。 carbonSecondary (2176。 ) C: a carbon bonded to two other carbons2176。 H: a hydrogen bonded to a 2176。 carbonTertiary (3176。 ) C: a carbon bonded to three other carbons3176。 H: a hydrogen bonded to a 3176。 carbonQuaternary (4176。 ) C: a carbon bonded to four other carbonsNomenclature IUPACParent name: the longest carbon chainSubstituent: a group bonded to the parent chain alkyl group: a substituent derived by removal of a hydrogen from an alkane。 given the symbol R1. Determine the number of carbons in the longest continuous carbon chain. This chain is called the parent hydrocarbon.2. The name of any alkyl substituent that hangs off the parent hydrocarbon is cited before the name of the parent hydrocarbon, together with a number to designate the carbon to which the alkyl substituent is attached.3. If more than one substituent is attached to the parent hydrocarbon, the chain is numbered in the direction that will result in the lowest possible number in the name of the pound.4. When both directions lead to the same lowest number for one of the substituents, the direction is chosen that gives the lowest possible number to one of the remaining substituents.5. If the same substituent numbers are obtained in both directions, the first group cited receives the lower number.6. If a pound has two or more chains of the same length, the parent hydrocarbon is the chain with the greatest number of substituents.7. Name the。