立体化学复习要点习题final

A中选择一个答案。而对于反应（4）中每个手性碳原子，要从B（1）R-(+)-CH3CH2CH(CH3)MgBr+O2H2O

CH3CH2CH(CH3)（3）CH3CH2COOH+Br2 产物使偏光平面向右旋产物使偏光平面向左旋（—(iV)产物是R产物是S在实验精确度范围内，恰好有一半产物是RS(iV)RS构型，而除了偶然的情况之外，二者是(V)下面的加成反应得到三种产物（36Cl表示标记氯）

+

+

薄荷酮（1）显示弱的正Cotton效应，而异薄荷酮（2）显示强的正Cotton效 10-甲基十氢萘酮（萘烷酮）Cotton效应，试问甲基的构型是怎样OH1 2 3 4 (3) HHeffect)通常Xa键的位置,试作出解释。YXYYXY在大多数的六元环情况下,环以反式相连比以顺式相连更稳定.当用碱处11-氧代素甲酯ⅱ（β-香树精衍生物）D/E环从顺式HEOHEOHDHHEOHDH

已经证明最初设想的对虫草酸（cordycepicacid[α]D=+4.03o）的结构（图）是不正确的。 人们怀疑最初结构的理由9b-ii(Phenalenol)优势构象的三HHH

OH3C H

O

H

优 HH

而不是

StatewhetherthefollowingsugarsarelorLabelthefollowingalkenesaseitherZorShowthatpropyleneandstyreneareprochiral,andlabelthefacesofpropyleneReorHowmanydiastereomersarethereforthefollowingcompound?Drawthemallwithchaircyclohexanerepresentations.Also,drawthemflatinthepageasshownbelow,exceptwithsoliddotsonthebridgeheadhydrogenstorepresentthecaseswherethehydrogensprojectDrawenantiomersofthefollowingIdentifythestereogeniccentersorunitsinthefollowingcompounds.(Stereogeniccenter.Anatomatwhichinterchangeofanytwoligandsproducesanewstereoisomer.Asynonymfor“stereocenter”.)Foreachstructureshown,labelthepairofmethylsashomotopic,enantiotopic,diastereotopic,orconstitutionallyheterotopic.(Homotopic.Therelationshipbetweentworegionsofamoleculethatarerelatedbyapropersymmetryoperation.;Enantiotopic.Therelationshipbetweentworegionsofamoleculethatarerelatedonlybyanimpropersymmetryoperation,typicallyamirrorne.;Heterotopic.ThesamegroupsoratomsininequivalentconstitutionalorstereochemicalIsthestructureshownchiral?IsitFindtheachirotopicpointsinthefollowingcompounds.Iftherearenoachirotopicpoints,statethis.Ifallpointsareachirotopic,statethisalso.(Achirotopic.Theoppositeofchirotopic.;Chirotopic.Thetermusedtodenotethatanatom,point,group,face,orlineresidesinachiralenvironment.)LabelanyCnorSnaxes(includingmirrornes)inthemoleculesinExerciseDrawadiastereomerofthefollowingmoleculethatisnotanFindtheprochiralhydrogensinthefollowingmolecules,andcircleanypro-Shydrogens.Iftherearenoprochiralhydrogens,statethis.Predictwhethertheproductratioofthefollowingreactionswillbe50:50oranumberotherthan50:50.ShowthatthehydrogensoftheCH2groupsofthefollowingmoleculesareneverequivalentinanyconformation.Foreachmoleculeshown,determinewhetherthetwofacesoftheolefinorcarbonylarehomotopic,enantiotopic,ordiastereotopic.Forethylphenylketone,designatetheReandSifaces.ShowthatthehydrogensoftheCH3groupofthefollowingmoleculesarenotequivalentintheconformationshown,butaverageduetobondrotation.Definethefollowingreactionsasstereoselectiveand/orstereospecific,andifso,determinethepercentstereoselectivityand/orstereospecificity.TheproductsinA,D,E,andFareasshown.TheproductratiosinBandCarehypotheticalforpurposesofthisquestion.Drawanymoleculethatcontainsanenantiotopicpairofhydrogensthatarenotattachedtothesameatom.WeshowedthatrapidrotationabouttheC1–C2bondof2-butanolmakesthethreehydrogensatC1symmetryeqWhyisitthatrapidrotationabouttheC2–C3bond(oranyotherbond)doesnotmakethetwohydrogensatC3e.Ferrocenehastwolimitingconformations,aneclipsedformandastaggeredform.EachhasanSnaxis.Whatisnforeach?Wediscussedthe“toplogicalrubberglove”,asysteminwhichtwoenantiomerscaninterconvertwithoutevergoingthroughanachiralform.Arelatedphenomenonwasobservedmuchearlierwiththebiphenylderivativeshown,firstpreparedbyMislow.Thenitrogroupsarelargeenoughthatthebiphenylscannotrotatepastoneanotheronanymeaningfultimescale.Convinceyourselfthata.thismoleculeischiral,b.theenantiomerscanreadilyinterconvertbyrotationsaboutsinglebonds,andc.atnotimeduringtheenantiomerizationisastructurethatisachiralForeachstructureshown,determinewhetherthetwomethylgroupsarehomotopic,enantiotopic,diastereotopic,orconstitutionallyheterotopic,bothonatimescalewhereringinversionisslowandonatimescalewhereringinversionisDrawthestereoisomersoftris(o-tolyl)borane.Whatbondrotationsarerequiredtointerconvertdiastereome