有机化学 英文课件 chapter3

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1、OrganicChemistryWilliamH.BrownChristopherS.FooteBrentL.IversonStereoisomerismandChiralityChapter3IsomersIsomers:differentcompoundswiththesamemolecularformulaConstitutionalisomers:isomerswithadifferentconnectivityStereoisomers:isomerswiththesameconnectivitybutadifferentorientationoftheiratomsinspa

2、ceChiralityChiral:fromtheGreek,cheir,handanobjectthatisnotsuperposableonitsmirrorimageAchiral:anobjectthatlackschirality;onethatlackshandednessanachiralobjecthasatleastoneelementofsymmetryplaneofsymmetry:animaginaryplanepassingthroughanobjectdividingitsothatonehalfisthemirrorimageoftheotherhalfce

3、nterofsymmetry:apointsosituatedthatidenticalcomponentsarelocatedonoppositesidesandequidistantfromthatpointalongtheaxispassingthroughitElementsofSymmetrySymmetryinobjectsElementsofSymmetryPlaneofsymmetry(cont’d)ChiralCenterThemostcommon(butnottheonly)causeofchiralityinorganicmoleculesisatetrahedra

4、latom,mostcommonlycarbon,bondedtofourdifferentgroupsAcarbonwithfourdifferentgroupsbondedtoitiscalledachiralcenterallchiralcentersarestereocenters,butnotallstereocentersarechiralcenters(seeFigure3.5)Enantiomers:stereoisomersthatarenonsuperposablemirrorimagesreferstotherelationshipbetweenpairsofobj

5、ectsEnantiomers2-Butanolhasonechiralcenterherearefourdifferentrepresentationsforoneenantiomerusing(4)asamodel,herearetwodifferentrepresentationsfortheenantiomerof(4)EnantiomersTheenantiomersoflacticaciddrawnintwodifferentrepresentationsEnantiomers2-ChlorobutaneEnantiomers3-ChlorocyclohexeneEnanti

6、omersAnitrogenchiralcenterR,SConventionPriorityrules1.Eachatombondedtothechiralcenterisassignedaprioritybasedonatomicnumber;thehighertheatomicnumber,thehigherthepriority2.Ifprioritycannotbeassignedpertheatomsbondedtothechiralcenter,looktothenextsetofatoms;priorityisassignedatthefirstpointofdiffer

7、enceR,SConvention3.AtomsparticipatinginadoubleortriplebondareconsideredtobebondedtoanequivalentnumberofsimilaratomsbysinglebondsNamingChiralCenters1.Locatethechiralcenter,identifyitsfoursubstituents,andassignpriorityfr