Simple Tricks in Organic Chemistry Figuring Out-R-S-Master-Organic-Chemistry PDF

Preview

Summary

Simple tricks in Organic Chemistry
...

Description

8/25/2016

SimpleTricksinOrganicChemistry:FiguringOutR/S—MasterOrganicChemistry

OnlineTutoring ReactionGuide StudyGuides Contact» MembersLogin» MasterOrganicChemistry Enteranorganicchemistrys

Preparing for Organic? Get an instant set of awesome "cheat sheets" for Org 1 and Org 2

New?StartHere StudyAndExamTips Organic1Index Organic2Index Free“CheatSheets” Feedback

Asimpletrick:The(R)(S)Toggle byJames inOrganicChemStudyTips,OrganicChemistry1,Stereochemistry

Thedifficultyofassigning(R)/(S)toastereocentercanbehighlydependentonthewaythemoleculeisdrawn. Forexample,assigningthestereochemistryofAshouldbeacakewalkifyouaretheleastbitfamiliarwiththe rules,whileBandCarealittlemoredifficult.Thethingis,you’renotalwaysgoingtobegivenastructure withthe4thrankedsubstituentintheback.OnethingIseestudentsdoalotinthissituationistrytoredrawthe structuretomakeiteasiertoassign(R)/(S)Whilethiscanbeeffective,itcaneasilyleadtomistakes. Furthermore,whenyou’redealingwithcyclicsystemslikemorphine[C],tryingtodrawthemirrorimageina reasonabletimeframemightinducebraintrauma.[Bytheway,forB,yourememberwhytheCH2CH2Br groupisranked3rd,right?[Note1]] Insteadofredrawingthewholemolecule,justleavethehydrogen(orother4thrankedsubstituent)infrontand figure out whether the substituents ranked 1 2 and 3 go clockwise or counterclockwise Then toggle (i e http://www.masterorganicchemistry.com/2010/03/13/asimpletricktherstoggle/

1/14

8/25/2016

SimpleTricksinOrganicChemistry:FiguringOutR/S—MasterOrganicChemistry

figureoutwhetherthesubstituentsranked1,2,and3goclockwiseorcounterclockwise.Thentoggle(i.e. reversedirectionCWtoCCWorviceversa)toaccountforthefactthatthe4thrankedsubstituentisinthefront, andassign(R)or(S)basedonthat.Youendupwiththesameanswerwithouthavingtoredrawanything. Wealsomakethesetypesofadjustmentswhenwe’relookinginmirrors.IfI’mlookinginamirroratyou holdingoutyourrighthand,Iaccountforthemirrorby“flipping”yourimagetoknowthatyouarereally holdingoutyourleft.It’sthesamethingwithmolecules.

Preparing for Organic? Get an instant set of awesome "cheat sheets" for Org 1 and Org 2

Thistrickseemsobvious,butI’vemetenoughpeoplewhodon’tdoittomakeitworthmentioning. Determining(R)/(S)eventuallybecomessecondnature,asdoestheabilitytoflip,rotateandinvertchemical structuresinyourhead.MuchlikeLondoncabdrivers,oneoftheinterestingsideeffectsofbecomingan organicchemististhatithyperdevelopsyourbrain’sspatialabilities. [note1–Priorityisdeterminedatthepointoffirstdifference.Hence,ofthetwocarbonsattachedtothe stereocenters,CH2andC=O,theC=Oisgivenpriority[O>H],regardlesssofwhetherahigherrankedelement isfurtherdownthesecondchain.] Tweet

0

0

RelatedPosts: TheSingleSwapRule EphedrineandPseudoephedrine TheMesoTrap OnCats,Part7:TheFischerProjection Taggedas:diastereomers,enantiomers,r/s,shortcuts,stereochemistry,tips {9comments…readthembeloworaddone}

mevans James http://www.masterorganicchemistry.com/2010/03/13/asimpletricktherstoggle/

2/14

8/25/2016

SimpleTricksinOrganicChemistry:FiguringOutR/S—MasterOrganicChemistry

Callmecrazy,butthestereocenterinCshouldbeR,right?Somuchforsecondnature…:P Reply

James Youarenotcrazy,I’manidiot.Fixed–Thanksforthecorrection! Reply

MichalSt Isthereatrickforrotationswhenthehydrogen(orotherfourthrankedsubstituent)isintheplaneofthe page? Reply Preparing for Organic? Get an instant set of awesome "cheat sheets" for Org 1 and Org 2

Yep–usethesingleswaprule(alater,improvedversionofthispost). http://masterorganicchemistry.com/2011/01/24/thesingleswaprule/ Reply

PavelS. HelloJames, Thanksforthewonderfullyorganizedwebsite.Ihadaquestionabouttheswaptrick– Weweretoldtovisualizemoleculesinclassandthetrickisnevertaughteventhoughtheinstructoris highlyratedandknowsit.Couldthisbebecauseitdoesnotworkinallcases? H | CCl WedgeOCH3HashCH3 TheaboveisjustsupposedtobeatetrahedralstructurewithHpointingupandClpointingright(bothare intheplaneofthepage).OnthebottomleftisanOCH3withawedge(comingoutofpage)andaCH3 onthebottomrightwithahash(goingintopage).ThepriorityisCl>OCH3>CH3.ThisgivesS. Accordingtotheswaprule,ifthehydrogenisnotpointingdownweswitchittoR,butthatwouldbe wrongbecauseifyouuseamolecularmodelkitandorientthestructure,youhaveS. AmIdoingsomethingwrongoristheRulenotahardsetruleandjustcorrect>90%ofthetime? Reply

James TheexampleIgavehasHinthefront.Ididn’tcoveranexamplewhereitisintheplaneofthe page. ThisisaVERYoldpost.AnevenbettertrickIfoundwastodothis:ifHisintheplaneofthe page,doasingleswapofHwithwhatevergroupisadash.ThendetermineR/S.Whatevervalue http://www.masterorganicchemistry.com/2010/03/13/asimpletricktherstoggle/

3/14

8/25/2016

SimpleTricksinOrganicChemistry:FiguringOutR/S—MasterOrganicChemistry

yougetwillbetheoppositeofthetrueR/S.Inyourexample,ifyouswapHwith(dashed)CH3, andthendetermineR/S,it“lookslike”R.Butsincewe’vedoneasingleswapit’stheoppositeof that–S–inaccordancewithwhatyousay. Relevantpost: http://www.masterorganicchemistry.com/2011/01/24/thesingleswaprule/ Reply

PavelS. Great.Thankyou! Ishouldhavereadthe“singleswaprule”morecarefully.You’veconfirmedformethatthe “R/Stoggle”methodabovedoesn’tworkinallcases.Thesingleswaprulemakessenseand ismoreuniversal.Thanksagain! Reply Preparing for Organic? Get an instant set of awesome "cheat sheets" for Org 1 and Org 2

DoestheR/SChartyoumadeupthereworkallthetime?Igettheswapruleandwholeideabehindit,but thischartmakeslifesomucheasier…. Reply

James Betterpost:http://www.masterorganicchemistry.com/2011/01/24/thesingleswaprule/ Reply LeaveaComment Name* Email* Website

Submit

SignUpToGetWeekly OrganicChemistryTips Andgetthefree"HowToSucceedInOrganicChemistry"Ebook Pleaseenteryourfirstname * http://www.masterorganicchemistry.com/2010/03/13/asimpletricktherstoggle/

4/14

8/25/2016

SimpleTricksinOrganicChemistry:FiguringOutR/S—MasterOrganicChemistry

FirstName Pleaseenteryouremail * Email

Signmeup!

AboutMasterOrganicChemistry Imaginehavingacomprehensiveonlineguidetohelpyousolveyourownproblemsin organicchemistry.That'smymissionwiththissite.AfterearningaPh.D.atMcGilland doingapostdocatMIT,Iappliedtobeaprofessor.Thatdidn'tworkout.SoIdecided toteachorganicchemistryanyway.MasterOrganicChemistryisthesiteIwishIhad whenIwaslearningthesubject.

GetTheLatestUpdates Preparing for Organic? Get an instant set of awesome "cheat sheets" for Org 1 and Org 2

twitter rss email RecentPosts PopularPosts RecentComments

StructureDeterminationCaseStudy:DeerTarsalGlandPheromonePostedon:Aug23, 2016 NaturalProductIsolation(2)PurificationofCrudeMixturesOverviewPostedon:Aug12, 2016

NaturalProductIsolation(1)ExtractionPostedon:Jul12,2016

NowAvailableTheSpectroscopyPack(PDF)Postedon:Jul07,2016 AGalleryofSomeInterestingMoleculesFromNaturePostedon:Apr21,2016 Copyright©2016MasterOrganicChemistry.com.Allrightsreserved OrganicChemistryIsAwesome AboutJames Account AdvancedSubstitutionTopics–SunNov10 AlkeneMiniCourse–Thanks! AlkeneMiniCourse AlkeneWebinar Alkenes:CommonExamProblems(WithSolutions) AlkyneWebinarSunDec15at9pmEST AlkynesAreABlankCanvas Blog http://www.masterorganicchemistry.com/2010/03/13/asimpletricktherstoggle/

5/14

8/25/2016

SimpleTricksinOrganicChemistry:FiguringOutR/S—MasterOrganicChemistry

Blog CancelSubscription CarbonCarbonBonds CommonMistakesInOrganicChemistry:PentavalentCarbon Confirmingyouremailaddress… CrashCourseOnAlkenes CrashCourseOnAlkenes–Checkout Dashboard Don’tBeFutyl,LearnTheButyls EliminationWebinar–SundayNov24at9pmEST Feedback FormStylingSandboxPage FromGenChemToOrganicChem GettingStarted Home Home2 HowToDrawACyclohexaneChair HowToSucceedInOrganicChemistry HowToSucceedInOrganicChemistry Initiation,Propagation,Termination Interview

Preparing for Organic? Get an instant set of awesome "cheat sheets" for Org 1 and Org 2

LeahNomenclatureGuestPost ManageSubscription MembersLogin Mission MOCElite MyOrganicChemistryStory–What’sYours? NewAcidBaseWebinar NEW!ReagentsApp October22AcidBaseWebinar OnlineOrganicChemistryTutoring Org2PostIndex Organic1 Organic2 OrganicChemistryStudyAdvice PostIndex PostIndex2 PostIndexDraft postindexdraft2 Products OrganicChemistryReagentGuide ReactionGuide 1,4additionofenolatestoenones(“TheMichaelReaction”) 1,4additionofnucleophilestoenones 1,4additionoforganocuprates(Gilmanreagents)toenones Acidiccleavageofethers(SN2) AdditionOfAlcoholsToAlkenesWithAcid Additionofaqueousacidtoalkenestogivealcohols AdditionofDichlorocarbenetoalkenestogivedichlorocyclopropanes Additionofdichloromethylenecarbenetoalkenes AdditionofGrignardreagentstoaldehydestogivesecondaryalcohols AdditionofGrignardreagentstoesterstogivetertiaryalcohols AdditionofGrignardreagentstoformaldehydetogiveprimaryalcohols AdditionofGrignardreagentstoketonestogivetertiaryalcohols AdditionofGrignardreagentstonitrilestogiveketones(afterhydrolysis) AdditionofHBroncetoalkynestogivealkenylbromides AdditionofHBrtoAlkenes Additi f HB t i t lk t i i l dib id

http://www.masterorganicchemistry.com/2010/03/13/asimpletricktherstoggle/

6/14

8/25/2016

SimpleTricksinOrganicChemistry:FiguringOutR/S—MasterOrganicChemistry

AdditionofHBrtwicetoalkynestogivegeminaldibromides AdditionofHCloncetoalkynestogivealkenylchlorides AdditionofHCltoAlkenestoGiveAlkylChlorides AdditionofHCltoalkynestwicetogivegeminaldichlorides AdditionofHIoncetoalkynestogivealkenyliodides AdditionofHItwicetoalkynestogivegeminaldiiodides AdditionofHydroiodicAcidtoAlkenestoGiveAlkylIodides AdditionofLiAlH4toaldehydestogiveprimaryalcohols AdditionofLiAlH4toketonestogivesecondaryalcohols AdditionofNaBH4toaldehydestogiveprimaryalcohols AdditionofNaBH4toketonestogivesecondaryalcohols Additionoforganocuprates(Gilmanreagents)toacidchloridestogiveketones Additiontoalkenesaccompaniedby1,2alkylshift Additionstoalkenesaccompaniedby1,2hydrideshifts Aldoladditionreactionofaldehydesandketones AldolCondensation Alkylationofenamineswithalkylhalides Alkylationofenolates AllylicbrominationofalkanesusingNBS BaeyerVilligerReaction Basepromotedformationofenolatesfromketones Preparing for Organic? Get an instant set of awesome "cheat sheets" for Org 1 and Org 2

BrominationofalkeneswithBr2togivedibromides Brominationofaromaticalkanestogivealkylbromides BrominationofAromaticstogiveBromoarenes CannizarroReaction ChlorinationofalkeneswithCl2togivevicinaldichlorides ChlorinationofArenestogiveChloroarenes ClaisenCondensationofesters Cleavageofethersusingacid(SN1reaction) ClemmensenReductionofKetones/AldehydestoAlkanes ConversionofacidchloridestoaldehydesusingLiAlH(OtBu)3 Conversionofacidchloridestoestersthroughadditionofanalcohol ConversionofalcoholstoalkylbromidesusingPBr3 ConversionofalcoholstoalkylchloridesusingSOCl2 ConversionofalcoholstoalkylhalidesusingHCl ConversionofAlkylhalidestoethers(SN1) ConversionofcarboxylicacidsintoacidchlorideswithSOCl2 Conversionofcarboxylicacidstocarboxylatesusingbase Conversionofcarboxylicacidstoestersusingacidandalcohols(FischerEsterification) ConversionoftertiaryalcoholstoalkylbromidesusingHBr ConversionoftertiaryalcoholstoalkyliodideswithHI ConversionofthioacetalstoalkanesusingRaneyNickel CurtiusRearrangementofAcylAzidestoIsocyanates Decarboxylationofbetaketocarboxylicacids Dehydrationofamidestogivenitriles Deprotonationofalcoholstogivealkoxides Deprotonationofalkyneswithbasetogiveacetylideions DielsAlderReactionofdienesanddienophiles DihydroxylationofAlkenestogive1,2diols(vicinaldiols) Dihydroxylationofalkeneswithcold,diluteKMnO4togivevicinaldiols Elimination(E1)ofalkylhalidestoformalkenes Elimination(E1)with1,2alkylshift Elimination(E1)withhydrideshift Elimination(E2)ofalkylhalidestogivealkenes EliminationofalcoholstogivealkenesusingPOCl3 Eliminationofwaterfromalcoholstoformalkenesusingacid EnamineHydrolysis F ti fA t l f Ald h d dK t

http://www.masterorganicchemistry.com/2010/03/13/asimpletricktherstoggle/

7/14

8/25/2016

SimpleTricksinOrganicChemistry:FiguringOutR/S—MasterOrganicChemistry

FormationofAcetalsfromAldehydesandKetones Formationofalkynesthroughdoubleeliminationofvicinaldibromides Formationofamidesfromacidchloridesandamines FormationofAmidesUsingDCC Formationofanhydridesfromacidhalidesandcarboxylates FormationofBromohydrinsfromalkenesusingwaterandBr2 FormationofbromohydrinsfromalkenesusingwaterandNBS FormationofCarboxylicAcidsfromAcylChlorides FormationofcarboxylicacidsfromGrignardreagentsandCO2 FormationofchlorohydrinsfromalkenesusingwaterandCl2 FormationofCyanohydrinsfromketonesandaldehydes Formationofcyclopropanesfromalkenesusingmethylenecarbene(:CH2) FormationofDiazoniumSaltsfromAromaticAmines Formationofenaminesfromketones/aldehydesandsecondaryamines FormationofepoxidesfromalkenesusingmCPBA Formationofepoxidesfrombromohydrins FormationofGilmanreagents(organocuprates)fromalkylhalides FormationofGrignardReagentsfromAlkenylHalides FormationofGrignardReagentsfromAlkylHalides Formationofhydratesfromaldehydes/ketonesandH2O Formationofiminesfromprimaryaminesandketones Preparing for Organic? Get an instant set of awesome "cheat sheets" for Org 1 and Org 2

Formationoftosylatesfromalcohols FreeRadicalAdditionofHBrToAlkenes FreeRadicalBrominationofAlkanes FreeRadicalChlorinationofAlkanes FriedelCraftsalkylationofarenes FriedelCraftsacylationofaromaticgroupstogiveketones HalogenationofAlkynes HellVollhardZelinskyReaction Hofmanneliminationofalkylammoniumsaltstogivealkenes HofmannRearrangementofAmidestoAmines HydroborationofAlkenes HydroborationofalkynesusingBH3togivealdehydes HydrogenationofAlkenestogiveAlkanes HydrogenationofAlkynestoAlkanesusingPd/C Hydrolysisofacetalstogivealdehydesandketones Hydrolysisofesterstocarboxylicacidswithaqueousacid Hydrolysisofiminestogiveketones(oraldehydes) Hydrolysisofnitrileswithaqueousacidtogivecarboxylicacids Iodinationofalkenestogivevicinaldiiodides(1,2diiodides) IodinationofAromaticswithI2 Ketoenoltautomerism KilianiFischerSynthesis Nitrationofaromaticgroups NucleophilicAromaticSubstitution(SNAr) NucleophilicAromaticSubstitutionViaArynes Openingofepoxideswithacidandwatertogivetransdiols Openingofepoxideswithnucleophilesunderacidicconditions OxidationofaldehydestocarboxylicacidsusingCr(VI) OxidationofaldehydestocarboxylicacidswithAg2O OxidationofaromaticalkaneswithKMnO4togivecarboxylicacids Oxidationofprimaryalcoholstoaldehydes OxidationofPrimaryAlcoholstoAldehydesusingPCC Oxidationofprimaryalcoholstocarboxylicacids OxidationofsecondaryalcoholstoketonesusingPCC Oxidationofthiolstodisulfides Oxidativecleavageof1,2diolstogivealdehydes/ketones O id ti l f lk t i k t / b li id i

http://www.masterorganicchemistry.com/2010/03/13/asimpletricktherstoggle/

(O3)

(“

id ti

8/14

8/25/2016

SimpleTricksinOrganicChemistry:FiguringOutR/S—MasterOrganicChemistry

Oxidativecleavageofalkenestogiveketones/carboxylicacidsusingozone(O3)–(“oxidative workup”) Oxidativecleavageofalkenestoketones/carboxylicacidsusingKMnO4 OxidativeCleavageofAlkyneswithKMnO4 OxidativeCleavageofAlkyneswithOzone(O3) OxymercurationofAlkenestoformEthersusingHg(OAc)2 OxymercurationofAlkynes Oxymercuration:AlcoholsfromalkenesusingHg(OAc)2andWater Ozonolysisofalkenestoketonesandaldehydes(reductiveworkup) Partialreductionofalkynestotransalkenesusingsodiumandammonia PartialreductionofalkyneswithLindlar’scatalysttogivecisalkenes PinacolRearrangement Polymerizationofdieneswithacid Protectionofalcoholsassilylethers Protonationofalcoholstogiveoxoniumions ProtonationofGrignardreagentstogivealkanes Reactionofalkylhalideswithwatertoformalcohols(SN1) Reactionofepoxideswithnucleophilesunderbasicconditions ReactionsofDiazoniumSalts ReductionofaromaticketonestoalkaneswithPd/Candhydrogen Reductionofaromaticnitrogroupstoaminogroups Preparing for Organic? Get an instant set of awesome "cheat sheets" for Org 1 and Org 2

ReductionofesterstoprimaryalcoholsusingLiAlH4 ReductionofnitrilestoprimaryamineswithLiAlH4 ReductiveAmination SharplessEpoxidation SN2ofCyanidewithAlkylHalidestogiveNitriles SN2reactionbetweenazideionandalkylhalidestogivealkylazides SN2ReactionofAcetylideIonswithAlkylHalides SN2reactionofalkoxideionswithalkylhalidestogiveethers(Williamsonsynthesis) SN2reactionofalkylhalideswithhydroxideionstogivealcohols SN2reactionofamineswithalkylchloridestogiveammoniumsalts SN2reactionofcarboxylateionswithalkylhalidestogiveesters SN2reactionofhydrosulfideionwithalkylhalidestogivethiols SN2reactionoforganocuprates(Gilmanreagents)withalkylhalidestogivealkanes SN2reactionofthiolateswithalkylhalidestogivethioethers(sulfides) SN2reactionofwaterwithalkylhalidestogivealcohols StilleReaction Substitution(SN1)withhydrideshift Substitutionwithaccompanyingalkylshift SulfonylationofArenestogivesulfonicacids SuzukiReaction TheGabrielsynthesisofamines Thehaloformreaction:conversionofmethylketonestocarboxylicacids TheHeckReaction TheMalonicEsterSynthesis TheMannichReaction TheRobinsonAnnulation Transesterificationpromotedbyalkoxides WittigReaction–conversionofketones/aldehydestoalkenes WolffKishnerReaction–conversionofketones/aldehydestoalkanes WolffRearrangement ResourceGuide Resources ShareYourOrganicChemistryStory SignUpForTheReactionGuide SignUpToBeAFlashcardsBetaTester! SignupfortheReactionGuide S thi H G W

http://www.masterorganicchemistry.com/2010/03/13/asimpletricktherstoggle/

9/14

8/25/2016

Simp...