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A中選擇一個答案。而對于反應(4)中每個手性碳原子,要從B(1)R-(+)-CH3CH2CH(CH3)MgBr+O2H2O

CH3CH2CH(CH3)(3)CH3CH2COOH+Br2 產(chǎn)物使偏光平面向右旋產(chǎn)物使偏光平面向左旋(—(iV)產(chǎn)物是R產(chǎn)物是S在實驗精確度范圍內(nèi),恰好有一半產(chǎn)物是RS(iV)RS構(gòu)型,而除了偶然的情況之外,二者是(V)下面的加成反應得到三種產(chǎn)物(36Cl表示標記氯)

+

+

薄荷酮(1)顯示弱的正Cotton效應,而異薄荷酮(2)顯示強的正Cotton效 10-甲基十氫萘酮(萘烷酮)Cotton效應,試問甲基的構(gòu)型是怎樣OH1 2 3 4 (3) HHeffect)通常Xa鍵的位置,試作出解釋。YXYYXY在大多數(shù)的六元環(huán)情況下,環(huán)以反式相連比以順式相連更穩(wěn)定.當用堿處11-氧代素甲酯ⅱ(β-香樹精衍生物)D/E環(huán)從順式HEOHEOHDHHEOHDH

已經(jīng)證明最初設(shè)想的對蟲草酸(cordycepicacid[α]D=+4.03o)的結(jié)構(gòu)(圖)是不正確的。 人們懷疑最初結(jié)構(gòu)的理由9b-ii(Phenalenol)優(yōu)勢構(gòu)象的三HHH

OH3C H

O

H

優(yōu) 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

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