Arrow pushing in organic chemistry an easy approach to understanding reaction mechanisms
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Levy, Daniel E.. Arrow-Pushing in Organic Chemistry : An Easy Approach to Understanding Reaction Mechanisms, John Wiley & Sons, Incorporated, 2017. ProQuest Ebook Central,
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Copyright © 2017. John Wiley & Sons, Incorporated. All rights reserved.
TableofContents
Cover
TitlePage
Preface
Acknowledgements
AbouttheAuthor
Chapter1:Introduction
1.1DEFINITIONOFARROWPUSHING
1.2FUNCTIONALGROUPS
1.3NUCLEOPHILESANDLEAVINGGROUPS
1.4SUMMARY
PROBLEMS
Chapter2:FreeRadicals
2.1WHATAREFREERADICALS?
2.2HOWAREFREERADICALSFORMED?
2.3FREERADICALSTABILITY
2.4WHATTYPESOFREACTIONSINVOLVEFREERADICALS?
2.5SUMMARY
PROBLEMS
Chapter3:Acids
3.1WHATAREACIDS?
3.2WHATISRESONANCE?
3.3HOWISACIDITYMEASURED?
3.4RELATIVEACIDITIES
3.5INDUCTIVEEFFECTS
3.6INDUCTIVEEFFECTSANDRELATIVEACIDITIES
3.7RELATIVEACIDITIESOFHYDROCARBONS
3.8SUMMARY
PROBLEMS
Chapter4:BasesandNucleophiles
4.1WHATAREBASES?
4.2WHATARENUCLEOPHILES?
Levy, Daniel E.. Arrow-Pushing in Organic Chemistry : An Easy Approach to Understanding Reaction Mechanisms, John Wiley & Sons, Incorporated, 2017. ProQuest Ebook Central,
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4.3LEAVINGGROUPS
4.4SUMMARY
PROBLEMS
Chapter5:SN2SubstitutionReactions
5.1WHATISANSN2REACTION?
5.2WHATARELEAVINGGROUPS?
5.3WHERECANSN2REACTIONSOCCUR?
5.4SN2′REACTIONS
5.5SUMMARY
PROBLEMS
Chapter6:SN1SubstitutionReactions
6.1WHATISANSN1REACTION?
Copyright © 2017. John Wiley & Sons, Incorporated. All rights reserved.
6.2HOWARESN1REACTIONSINITIATED?
6.3THECARBOCATION
6.4CARBOCATIONREARRANGEMENTS
6.5SUMMARY
PROBLEMS
Chapter7:EliminationReactions
7.1E1ELIMINATIONS
7.2E1cBELIMINATIONS
7.3E2ELIMINATIONS
7.4HOWDOELIMINATIONREACTIONSWORK?
7.5E1cBELIMINATIONSVERSUSE2ELIMINATIONS
7.6SUMMARY
PROBLEMS
Chapter8:AdditionReactions
8.1ADDITIONOFHALOGENSTODOUBLEBONDS
8.2MARKOVNIKOV’SRULE
8.3ADDITIONSTOCARBONYLS
8.4SUMMARY
PROBLEMS
Chapter9:Carbenes
9.1WHATARECARBENES?
Levy, Daniel E.. Arrow-Pushing in Organic Chemistry : An Easy Approach to Understanding Reaction Mechanisms, John Wiley & Sons, Incorporated, 2017. ProQuest Ebook Central,
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9.2HOWARECARBENESFORMED?
9.3REACTIONSWITHCARBENES
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9.4CARBENESVERSUSCARBENOIDS
9.5SUMMARY
PROBLEMS
Chapter10:PericyclicReactions
10.1WHATAREPERICYCLICREACTIONS?
10.2ELECTROCYCLICREACTIONS
10.3CYCLOADDITIONREACTIONS
10.4SIGMATROPICREACTIONS
10.5SUMMARY
PROBLEMS
Chapter11:MovingForward
11.1FUNCTIONALGROUPMANIPULATIONS
11.2NAMEREACTIONS
11.3REAGENTS
11.4FINALCOMMENTS
PROBLEMS
Appendix1:pKaValuesofProtonsAssociatedwithCommonFunctionalGroups
Appendix2:AnswersandExplanationstoProblems
Appendix3:StudentReactionGlossary
Index
PeriodicTableofElements
EndUserLicenseAgreement
ListofTables
Chapter11
Table11.1Namereactionsandreactiontypesusefulformodificationandexpansionof
organicstructures.
Table11.2Reagentclassesandassociatedproperties.
ListofIllustrations
Chapter01
Levy, Daniel E.. Arrow-Pushing in Organic Chemistry : An Easy Approach to Understanding Reaction Mechanisms, John Wiley & Sons, Incorporated, 2017. ProQuest Ebook Central,
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Scheme1.1ExampleoftheWittigreaction.
Scheme1.2ExampleoftheDiels–Alderreaction.
Scheme1.3Exampleofatinhydridedehalogenation.
Figure1.1Examplesofchemicalbonds.
Figure1.2Examplesofchemicalbondsandlonepairs.
Scheme1.4Illustrationofhomolyticcleavage.
Scheme1.5Illustrationofheterolyticcleavage.
Scheme1.6Illustrationofaconcertedreaction(Coperearrangement).
Scheme1.7IllustrationofarrowpushingappliedtotheCoperearrangement.
Scheme1.8Applicationofarrowpushingtohomolyticcleavageusingsinglebarbed
arrows.
Scheme1.9Applicationofarrowpushingtoheterolyticcleavageusingdouble
barbedarrows.
Figure1.3Commonorganicfunctionalgroups.
Figure1.4Howfunctionalgroupsinfluencepolarity.
Scheme1.10Exampleofanucleophilicreaction.
Chapter02
Figure2.1Tetheredballmodelforbondstrain.
Figure2.2Tetheredballmodelforbreakingbonds.
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Figure2.3Translationoftetheredballmodeltoanions,cations,andfreeradicals.
Figure2.4Commonfreeradicals.
Figure2.5Formationofradicalionsviaelectrontransfer.
Scheme2.1HomolyticcleavageofNbromosuccinimide.
Figure2.6Commonfreeradicalinitiators.
Figure2.7Conjugatedaromaticringsystemsformradicalanionsmorereadily.
Scheme2.2Freeradicalsreadilypairformingcovalentbonds.
Figure2.8Molecularstructuresofgraphiteanddiamond.
Figure2.9Orderoffreeradicalstability.
Figure2.10Hydrogenatomsorbitalscandonateelectrondensitytoadjacentcentersof
electrondeficiencyascanheteroatomsbearingloneelectronpairs.
Scheme2.3Examplesofbrominationreactions.
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Scheme2.4Arrowpushingmechanismforbrominationofmethane.
Scheme2.5Allylicandbenzylicbromination(halogenation).
Scheme2.6Freeradicalsstabilizedbyconjugationcanformmultipleproducts.
Figure2.11Commonorganicpolymers.
Scheme2.7Freeradicalformationofpolystyrene.
Scheme2.8Terminationofpolystyrenefreeradicalpolymerization.
Scheme2.9Examplesofoxidativefunctionalgrouptransformations.
Scheme2.10Mechanismforautoxidationofisobutane.
Chapter03
Scheme3.1Generalrepresentationofaciddissociation.
Figure3.1Solventeffectsonaciddissociation.
Figure3.2Commonpolarandnonpolarorganicsolvents.
Scheme3.2Dissociationofacarboxylicacidformingaprotonandacarboxylate
anion.
Scheme3.3Resonanceformsofthecarboxylateanion.
Scheme3.4Rationalizationofthecarboxylateanionresonanceformsusingarrow
pushing.
Scheme3.5Dimethylmalonatedoesnotspontaneouslyliberatemalonateanions.
Scheme3.6Potassiumtertbutoxidepartiallydeprotonatesdimethylmalonate.
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Scheme3.7Resonanceformsofthemalonateanionrationalizedusingarrowpushing.
Figure3.3Definitionoftheequilibriumconstant( Keq ).
Figure3.4KaistheKeqspecificallyrelatedtodissociationofacids.
Figure3.5DefinitionofpH.
Figure3.6DefinitionofpKa.
Figure3.7pKavaluesarerelatedtopH.
Figure3.8TheHenderson–Hasselbalchequation.
Figure3.9Inaperfectequilibrium,pKa = pH.
Figure3.10Representativefunctionalgroupswithassociatedacidicprotons.
Figure3.11Representativefunctionalgroupswithadjacentacidicprotons.
Scheme3.8Resonancecapabilitiesofcarboxylicacidscomparedtoalcohols.
Levy, Daniel E.. Arrow-Pushing in Organic Chemistry : An Easy Approach to Understanding Reaction Mechanisms, John Wiley & Sons, Incorporated, 2017. ProQuest Ebook Central,
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Figure3.12CommoncarboxylicacidsandtheirrespectivepKavalues.
Scheme3.9Esterscanbedeprotonatedαtoestercarbonyls.
Scheme3.10Rationalizationoftheacidityofprotonsαtoestercarbonyls.
Scheme3.11Electronwithdrawinggroupsincreaseaciditybyincreasinganionic
stability.
Scheme3.12Electrondonatinggroupsdecreaseaciditybydecreasinganionic
stability.
Figure3.13Commonelectronwithdrawinggroupsandelectrondonatinggroups.
Figure3.14pKavaluesassociatedwithalcoholsincreaseasalkylbranchingincreases.
Scheme3.13Aminesandalcoholscanbothbedeprotonated.
Scheme3.14HydrocarbonscanbedeprotonatedandhavemeasurablepKavalues.
Chapter04
Scheme4.1Generalrepresentationofbasesreactingwithacids.
Figure4.1Commonbasesusedinorganicchemistry.
Scheme4.2Equilibriumbetweenmethylacetateandtriethylamine.
Scheme4.3Equilibriumbetweenmethylacetateandpotassiumtertbutoxide.
Scheme4.4Equilibriumbetweenmethylacetateandphenyllithium.
Scheme4.5Aminebasicityisrelatedtothenitrogenlonepair.
Scheme4.6Alcoholandetheroxygenscanbeprotonated.
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Scheme4.7Carboxylicacidsandesterscanbeprotonated.
Scheme4.8Aldehydesandketonescanbeprotonated.
Scheme4.9Carbonylbasedfunctionalgroupsdelocalizechargesthroughresonance.
Scheme4.10Protonatedcarbonylbasedfunctionalgroupsdelocalizetheirpositive
charges.
Scheme4.11Protonatedcarbonylbasedfunctionalgroupsaresusceptibletoreaction
withnucleophiles.
Figure4.2Representativenucleophilesandtheircorrespondingacidforms.
Figure4.3Relationshipbetweennucleophilicity,electronegativity,andbasicityas
illustratedusingfirstrowelements.
Figure4.4Theorderofincreasingnucleophilicityofhalideionsisinfluencedby
polarizinginfluencessuchassolventeffects.
Figure4.5Solventshellssurroundhardbasesmoreclosely,makingthemlessreactive
Levy, Daniel E.. Arrow-Pushing in Organic Chemistry : An Easy Approach to Understanding Reaction Mechanisms, John Wiley & Sons, Incorporated, 2017. ProQuest Ebook Central,
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nucleophilescomparedwithsoftbases.
Figure4.6StericeffectscanoverridetheinfluenceofpKavaluesonnucleophilicity.
Scheme4.12Exampleofanucleophilicreaction.
Chapter05
Scheme5.1RepresentationofanSN2reaction.
Figure5.1Enantiomersaremirrorimages,notsuperimposableanddependentuponthe
tetrahedralarrangementofcarbonatomsubstituents.
Scheme5.2MechanisticexplanationofSN2reactions.
Scheme5.3SN2reactionsproceedwhenincomingnucleophilesaremorenucleophilic
thanoutgoingleavinggroups.
Scheme5.4SN2reactionsdonotproceedwhenincomingnucleophilesareless
nucleophilicthanoutgoingleavinggroups.
Figure5.2Chloromethanebearsapartialnegativechargeontheelectronegative
chlorineatomandapartialpositivechargeonthecarbonatom.
Figure5.3Thecarbon–chlorinebondinchloromethaneispolarized.
Scheme5.5Understandingthedirectionofbondpolarityallowsidentificationof
reactionsite,trajectoryofnucleophile,andidentificationoftheleavinggroup.
Scheme5.6StericbulkslowsdownreactionratesforSN2reactions.
Scheme5.7Resonanceformscanbeusedtorationalizethestabilityofcationsadjacent
tositesofbondunsaturation.
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Figure5.4Partialchargescanbedelocalizedthroughunsaturatedbonds.
Scheme5.8ComparisonofSN2andSN2′reactionsasexplainedwitharrowpushing.
Scheme5.9CompetingSN2andSN2′reactionmechanismscanleadtoproduct
mixtures.
Chapter06
Scheme6.1TheinitialphaseofanSN1reactioninvolvesdissociationofaleaving
groupfromthestartingmoleculegeneratingacarbocation.
Scheme6.2ThesecondphaseofanSN1reactioninvolvesreactionofacarbocation
withanucleophilegeneratinganewproduct.
Scheme6.3SolvolysisoftertbutylbromideinmethanolproducesMTBEviaanS
mechanism.
Scheme6.4Explanationofthesolvolysisoftertbutylbromideinmethanolusing
Levy, Daniel E.. Arrow-Pushing in Organic Chemistry : An Easy Approach to Understanding Reaction Mechanisms, John Wiley & Sons, Incorporated, 2017. ProQuest Ebook Central,
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N1
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arrowpushing.
Scheme6.5MethanolwillnotreactwithtertbutylbromideviaanS
N2mechanism.
Figure6.1Fullysubstitutedcarbonatomspresentsubstituentsintetrahedral
arrangements.
Figure6.2sOrbitalsaresphericalandporbitalsareshapedlikehourglasses.
Figure6.3Hybridorbitalsresultfromcombinationsofsandporbitals.
Figure6.4Likesubstituents,lonepairsinfluencemoleculargeometry.
Figure6.5Differentorbitalhybridizationsresultsindifferentmoleculargeometries.
Figure6.6sp2Hybridizedcarbocationspossesstrigonalplanargeometries.
Scheme6.6ThestereochemicalcoursesofSN2reactionsaredefinedbythe
stereochemicalconfigurationofthestartingmaterials—oneproductisformed.
Scheme6.7ThestereochemicalidentitiesofstartingmaterialssubjectedtoSN1
reactionsarelostduetotheplanarityofreactivecarbocations—twoproductsare
formed.
Figure6.7Tertiarycarbocationsaremorestablethansecondarycarbocations,and
secondarycarbocationsaremorestablethanprimarycarbocations.
Figure6.8Hydrogenatomsorbitalscandonateelectrondensitytoadjacentcationic
centersascanheteroatomsbearingloneelectronpairs.
Figure6.9Heteroatomsstabilizecarbocationsbetterthanhyperconjugationeffects.
Figure6.10Allyliccarbocationsaremorestablethansecondarycarbocations.
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Figure6.11Tertiarycarbocationsaremorestablethanallyliccarbocations.
Figure6.12Hyperconjugationoccurswhenacarbon–hydrogenbondliesinthesame
planeasacarbocation’svacantporbital.
Figure6.13Hyperconjugationcanbeviewedasformationofa“pseudodouble
bond.”
Scheme6.8Hyperconjugationleadstomigrationofhydrogenatomsthrougha1,2
hydrideshift.
Scheme6.9Rearrangementsvia1,2hydrideshiftsgeneratemorestablecarbocations
fromlessstablecarbocations.
Scheme6.10Thepinacolrearrangement.
Scheme6.11Thepinacolrearrangementproceedsthroughsolvolysismediatedcation
formation.
Scheme6.121,2Hydrideshiftswillnotoccurwhentheproductcationislessstable
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thanthestartingcation.
Scheme6.13Alkylmigrationsoccurwhentheresultingcarbocationismorestablethan
thestartingcarbocation.
Scheme6.14Conclusionofthepinacolrearrangementinvolvesmigrationofthe
positivechargetotheadjacentoxygenatomfollowedbydeprotonation.
Chapter07
Figure7.1Hyperconjugationoccurswhenacarbon–hydrogenbondliesinthesame
planeasacarbocation’svacantporbital.
Figure7.2Hyperconjugationcanbeviewedasformationofa“pseudodoublebond.”
Scheme7.1Dissociationofaprotonthroughhyperconjugationcompletesthefinalstage
ofanE1eliminationmechanism.
Scheme7.2E1mechanismsexplainadditionalproductsobservedduringSN1
reactions.
Scheme7.3Solvolysisof2bromo2,3dimethylpentaneinmethanolleadsto
formationofuptosixdifferentproductsviamultiplemechanisticpathways.
Scheme7.4Generalrepresentationofbases(BorB−)reactingwithacids(HA)
formingconjugatebases(A−).
Scheme7.5Formationoftheconjugatebaseandassociatedresonancestructure
resultingfromthereactionof2iodomethyldimethylmalonatewithsodiumhydride.
Scheme7.6βEliminationoftheiodidecompletestheE1cBmechanismconvertingthe
2iodomethyldimethylmalonateanionto2methylidenedimethylmalonate.
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Scheme7.7Reactionof2iodomethyldimethylmalonatewithanucleophileresultsin
predominantformationoftheE1cBeliminationproduct.
Scheme7.8SN2substitutionreactionscanoccurincompetitionwithE2elimination
reactions.
Figure7.3Tertiarycarbocationsaremorestablethansecondarycarbocations,and
secondarycarbocationsaremorestablethanprimarycarbocations.
Figure7.4Whenacarbon–hydrogen(orcarbonalkyl)bondisalignedwithanempty
porbital,1,2hydride/alkylshiftsandE1eliminationsarefavorable.
Figure7.5Whenacarbon–hydrogenbondoranegativelychargedorbitalisaligned
transperiplanarwithacarbonleavinggroupbond,E2eliminationsandE1cB
eliminationsarefavorable.
Scheme7.9E2eliminationsdependuponthepresenceoftransperiplanar
relationships.
Scheme7.10MechanisticprogressionofE2eliminations.
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Scheme7.11Iftransperiplanarrelationshipscanbeestablished,E2elimination
productscanform.
Chapter08
Scheme8.1Additionofbrominetoethylene.
Scheme8.2Molecularbrominereactswithdoublebondsgeneratingabromoniumion
andabromideanion.
Scheme8.3Bromoniumionspossesselectrophiliccarbonatoms.
Scheme8.4Nucleophilicreactionbetweenabromideanionandabromoniumion
generates1,2dibromoalkanes.
Scheme8.5Proticacidscanaddacrossdoublebonds.
Scheme8.6Doublebondscanbecomeprotonatedunderacidicconditions.
Scheme8.7Nucleophilesaddtoprotonatedolefins.
Scheme8.8Multiplepotentialproductsarepossiblefromadditionofproticacids
acrossdoublebonds.
Scheme8.9Protonationofpropeneintroducescationiccharactertobothprimaryand
secondarycenters.
Figure8.1Whileunsubstitutedolefinsarenonpolar,carbonylsarepolar.
Scheme8.10Nucleophilescanaddtocarbonylstoformalcohols.
Scheme8.11Additionofnucleophilestocarbonylscanbereversible.
Scheme8.12Productsresultingfromadditionofnucleophilestoacetone.
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Scheme8.13Carbonylscanbecomeprotonated.
Scheme8.14Additionofnucleophilestocarbonylscanoccurunderacidicconditions.
Scheme8.15Additionofnucleophilestosimplecarbonylsresultsin1,2additions.
Figure8.2ComparisonofSN2andSN2′reactionsasexplainedwitharrowpushing.
Scheme8.16Additionofnucleophilestoα,βunsaturatedcarbonylgroupsas
explainedusingarrowpushing.
Scheme8.17Additionofnucleophilestoα,βunsaturatedcarbonylscanresultin1,4
additions.
Scheme8.18α,βUnsaturatedcarbonylsystemscanbesequentiallysubjectedto1,4
additionsand1,2additions.
Figure8.3Unlikemostcarbonylbasedfunctionalgroups,nonconjugatedesterscan
reactwithnucleophilesandretainthecarbonylunit.
Scheme8.19Theaddition–eliminationmechanismillustratedwitharrowpushing.
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Figure8.4Functionalgroupscapableofparticipatinginaddition–elimination
reactions.
Chapter09
Figure9.1Structuralrepresentationsofcarbenesusingdotnotation,inclusionof
orbitalsandrepresentativeillustrationofneutralizingcharges.
Scheme9.1Chloroformcanbedeprotonatedinthepresenceofstrongbases.
Scheme9.2αEliminationversusβelimination.
Figure9.2Generalrepresentationofdiazocompoundsandresonanceforms.
Scheme9.3Decompositionofdiazocompoundsleadstocarbeneformation.
Figure9.3Representationofcarbenedimerization.
Scheme9.4Reactionofdichlorocarbenewiththetrichloromethylanion.
Scheme9.5Reactionoftheethylacetatecarbenewithethyldiazoacetate.
Scheme9.6ExampleofcyclopropaneformationbyintramolecularSN2reaction.
Figure9.4Hyperconjugationcanbeviewedasa“protonationofadoublebond.”
Scheme9.7Thecarbeneemptyporbitalcandirectlyinteractwithanolefinleadingto
cyclopropaneringformation.
Scheme9.8Carbeneadditionstoolefinsgeneratesynproducts.
Scheme9.9Dichlorocarbeneproducesdifferentproductsfromcisandtransolefins.
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Figure9.5Reactionofcis2butenewithdichlorocarbeneproducesthesameproduct
frombothtopandbottomapproachesofdichlorocarbene.
Figure9.6Reactionoftrans2butenewithdichlorocarbeneresultsinformationof
enantiomers.
Scheme9.10Cyclopropanationproductsareinfluencedbythetrajectory(topvs.
bottom)ofthecarbeneandbythespatialorientationofthecarbene.
Scheme9.11CarbeneO—HinsertionreactionsarecomplementarytotheWilliamson
EtherSynthesis.
Figure9.7Examplebasemediatedsidereactionsavoidedusingcarbeneinsertion
reactions.
Scheme9.12Formationofacarbenoidonreactionofethyldiazoacetatewith
rhodium(II)acetate.
Chapter10
Figure10.1Cyclictransitionstatesenableprogressionofpericyclicreactions.
Figure10.2σBondsandπbondscomprisemolecularorbitalsformedfromthe
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overlapofsorbitals,porbitals,andcombinationsthereof.
Scheme10.1Electrocyclicconversionofcis1,3,5hexatrieneto1,3
cyclohexadiene.
Figure10.3Substitutionpatternscanimpacttherateandsuccessofelectrocyclic
reactions.
Scheme10.2Electrocyclicreactionsinvolvingfourmemberedrings,eight
memberedrings,andbicyclicringsystems.
Scheme10.3Stereochemicalcoursesforelectrocyclicreactionsformingsix
memberedandeightmemberedrings.
Scheme10.4Diels–Alderreactionwith1,2butadieneandethylene.
Figure10.4Diene–dienophileorientationsforDiels–Alderreactionprogression.
Scheme10.5Diels–Alderreactionbetweencyclopentadieneandacrolein.
Figure10.5ExampledienesanddienophilesusefulinDiels–Alderreactions.
Scheme10.6Enereactionwithpropyleneandethylene.
Scheme10.7Enereactionbetween1buteneandacrylonitrile.
Scheme10.8Intramolecularenereactionscanformsubstitutedringsystems.
Figure10.6Examplesofdipolarmoleculesanddipolarfunctionalgroups.
Scheme10.9Examplesof1,3dipolarcycloadditions.
Figure10.71,3Dipolescanapproachdipolarophileintwopossibleorientations.
Scheme10.10Mechanisticpathwayforozonolysisreactions.
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Scheme10.11Coperearrangementof1,5hexadiene.
Scheme10.12Coperearrangementof3methyl1,5hexadiene.
Scheme10.13OxyCoperearrangementof3hydroxy1,5hexadiene.
Scheme10.14Claisenrearrangementofallylphenylether.
Scheme10.15MultipleClaisenrearrangementscanbeusedtogeneratephenol
structureswithmultiplesubstitutions.
Scheme10.16Allylacetatecanbeconvertedintoasilylketeneacetalprecursorforthe
Ireland–Claisenrearrangement.
Scheme10.17TheIreland–Claisenrearrangementgeneratescarboxylicacidswith
terminaldoublebonds.
Scheme10.18ExampleoftheJohnson–Claisenrearrangement.
Figure10.8Examplesoforthoesters.
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Scheme10.19MechanismfortheJohnson–Claisenrearrangement.
Chapter11
Scheme11.1Additionofbromineacrossadoublebond.
Scheme11.2Markovnikovadditionofhydrobromicacidacrossadoublebond.
Figure11.1FunctionalgroupsavailablefromalkylhalidesviaSN1andSN2
mechanisms.
Scheme11.3Conversionofalcoholstoethers—theWilliamsonethersynthesis.
Figure11.2Transformationsofcarboxylicacidstoestersandamides.
Figure11.3Transformationsofesterstocarboxylicacidsandamides.
Figure11.4Transformationsofaldehydesandketonestoimines,oximes,andenamines.
Figure11.5Oxidativeandreductiveconversionsoffunctionalgroups.
Scheme11.4TheDiels–Alderreaction.
Scheme11.5TheCoperearrangement.
Scheme11.6TheClaisenrearrangement.
Scheme11.7Thepinacolrearrangement.
Scheme11.8TheFavorskiirearrangement.
Scheme11.9Thealdolcondensation.
Scheme11.10TheRobinsonannulation.
Scheme11.11Alkylationandacylationreactionsadjacenttocarbonyls.
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Scheme11.12TheFriedel–Craftsacylation.
Scheme11.13TheWittigreaction.
Scheme11.14TheHorner–Emmonsreaction.
Scheme11.15Acation–πcyclization.
Scheme11.16TheGrignardreaction.
Scheme11.17FormationofGrignardreagentsinvolvesoxidativeaddition.
Scheme11.18TheSuzukireaction.
Scheme11.19SimplifiedSuzukireactionmechanism.
Scheme11.20TheMichaeladdition.
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ArrowPushinginOrganicChemistry
AnEasyApproachtoUnderstandingReaction
Mechanisms
SecondEdition
DanielE.Levy
Copyright © 2017. John Wiley & Sons, Incorporated. All rights reserved.
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Copyright © 2017. John Wiley & Sons, Incorporated. All rights reserved.
TableofContents
Cover
TitlePage
Preface
Acknowledgements
AbouttheAuthor
Chapter1:Introduction
1.1DEFINITIONOFARROWPUSHING
1.2FUNCTIONALGROUPS
1.3NUCLEOPHILESANDLEAVINGGROUPS
1.4SUMMARY
PROBLEMS
Chapter2:FreeRadicals
2.1WHATAREFREERADICALS?
2.2HOWAREFREERADICALSFORMED?
2.3FREERADICALSTABILITY
2.4WHATTYPESOFREACTIONSINVOLVEFREERADICALS?
2.5SUMMARY
PROBLEMS
Chapter3:Acids
3.1WHATAREACIDS?
3.2WHATISRESONANCE?
3.3HOWISACIDITYMEASURED?
3.4RELATIVEACIDITIES
3.5INDUCTIVEEFFECTS
3.6INDUCTIVEEFFECTSANDRELATIVEACIDITIES
3.7RELATIVEACIDITIESOFHYDROCARBONS
3.8SUMMARY
PROBLEMS
Chapter4:BasesandNucleophiles
4.1WHATAREBASES?
4.2WHATARENUCLEOPHILES?
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4.3LEAVINGGROUPS
4.4SUMMARY
PROBLEMS
Chapter5:SN2SubstitutionReactions
5.1WHATISANSN2REACTION?
5.2WHATARELEAVINGGROUPS?
5.3WHERECANSN2REACTIONSOCCUR?
5.4SN2′REACTIONS
5.5SUMMARY
PROBLEMS
Chapter6:SN1SubstitutionReactions
6.1WHATISANSN1REACTION?
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6.2HOWARESN1REACTIONSINITIATED?
6.3THECARBOCATION
6.4CARBOCATIONREARRANGEMENTS
6.5SUMMARY
PROBLEMS
Chapter7:EliminationReactions
7.1E1ELIMINATIONS
7.2E1cBELIMINATIONS
7.3E2ELIMINATIONS
7.4HOWDOELIMINATIONREACTIONSWORK?
7.5E1cBELIMINATIONSVERSUSE2ELIMINATIONS
7.6SUMMARY
PROBLEMS
Chapter8:AdditionReactions
8.1ADDITIONOFHALOGENSTODOUBLEBONDS
8.2MARKOVNIKOV’SRULE
8.3ADDITIONSTOCARBONYLS
8.4SUMMARY
PROBLEMS
Chapter9:Carbenes
9.1WHATARECARBENES?
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9.2HOWARECARBENESFORMED?
9.3REACTIONSWITHCARBENES
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9.4CARBENESVERSUSCARBENOIDS
9.5SUMMARY
PROBLEMS
Chapter10:PericyclicReactions
10.1WHATAREPERICYCLICREACTIONS?
10.2ELECTROCYCLICREACTIONS
10.3CYCLOADDITIONREACTIONS
10.4SIGMATROPICREACTIONS
10.5SUMMARY
PROBLEMS
Chapter11:MovingForward
11.1FUNCTIONALGROUPMANIPULATIONS
11.2NAMEREACTIONS
11.3REAGENTS
11.4FINALCOMMENTS
PROBLEMS
Appendix1:pKaValuesofProtonsAssociatedwithCommonFunctionalGroups
Appendix2:AnswersandExplanationstoProblems
Appendix3:StudentReactionGlossary
Index
PeriodicTableofElements
EndUserLicenseAgreement
ListofTables
Chapter11
Table11.1Namereactionsandreactiontypesusefulformodificationandexpansionof
organicstructures.
Table11.2Reagentclassesandassociatedproperties.
ListofIllustrations
Chapter01
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Scheme1.1ExampleoftheWittigreaction.
Scheme1.2ExampleoftheDiels–Alderreaction.
Scheme1.3Exampleofatinhydridedehalogenation.
Figure1.1Examplesofchemicalbonds.
Figure1.2Examplesofchemicalbondsandlonepairs.
Scheme1.4Illustrationofhomolyticcleavage.
Scheme1.5Illustrationofheterolyticcleavage.
Scheme1.6Illustrationofaconcertedreaction(Coperearrangement).
Scheme1.7IllustrationofarrowpushingappliedtotheCoperearrangement.
Scheme1.8Applicationofarrowpushingtohomolyticcleavageusingsinglebarbed
arrows.
Scheme1.9Applicationofarrowpushingtoheterolyticcleavageusingdouble
barbedarrows.
Figure1.3Commonorganicfunctionalgroups.
Figure1.4Howfunctionalgroupsinfluencepolarity.
Scheme1.10Exampleofanucleophilicreaction.
Chapter02
Figure2.1Tetheredballmodelforbondstrain.
Figure2.2Tetheredballmodelforbreakingbonds.
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Figure2.3Translationoftetheredballmodeltoanions,cations,andfreeradicals.
Figure2.4Commonfreeradicals.
Figure2.5Formationofradicalionsviaelectrontransfer.
Scheme2.1HomolyticcleavageofNbromosuccinimide.
Figure2.6Commonfreeradicalinitiators.
Figure2.7Conjugatedaromaticringsystemsformradicalanionsmorereadily.
Scheme2.2Freeradicalsreadilypairformingcovalentbonds.
Figure2.8Molecularstructuresofgraphiteanddiamond.
Figure2.9Orderoffreeradicalstability.
Figure2.10Hydrogenatomsorbitalscandonateelectrondensitytoadjacentcentersof
electrondeficiencyascanheteroatomsbearingloneelectronpairs.
Scheme2.3Examplesofbrominationreactions.
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Scheme2.4Arrowpushingmechanismforbrominationofmethane.
Scheme2.5Allylicandbenzylicbromination(halogenation).
Scheme2.6Freeradicalsstabilizedbyconjugationcanformmultipleproducts.
Figure2.11Commonorganicpolymers.
Scheme2.7Freeradicalformationofpolystyrene.
Scheme2.8Terminationofpolystyrenefreeradicalpolymerization.
Scheme2.9Examplesofoxidativefunctionalgrouptransformations.
Scheme2.10Mechanismforautoxidationofisobutane.
Chapter03
Scheme3.1Generalrepresentationofaciddissociation.
Figure3.1Solventeffectsonaciddissociation.
Figure3.2Commonpolarandnonpolarorganicsolvents.
Scheme3.2Dissociationofacarboxylicacidformingaprotonandacarboxylate
anion.
Scheme3.3Resonanceformsofthecarboxylateanion.
Scheme3.4Rationalizationofthecarboxylateanionresonanceformsusingarrow
pushing.
Scheme3.5Dimethylmalonatedoesnotspontaneouslyliberatemalonateanions.
Scheme3.6Potassiumtertbutoxidepartiallydeprotonatesdimethylmalonate.
Copyright © 2017. John Wiley & Sons, Incorporated. All rights reserved.
Scheme3.7Resonanceformsofthemalonateanionrationalizedusingarrowpushing.
Figure3.3Definitionoftheequilibriumconstant( Keq ).
Figure3.4KaistheKeqspecificallyrelatedtodissociationofacids.
Figure3.5DefinitionofpH.
Figure3.6DefinitionofpKa.
Figure3.7pKavaluesarerelatedtopH.
Figure3.8TheHenderson–Hasselbalchequation.
Figure3.9Inaperfectequilibrium,pKa = pH.
Figure3.10Representativefunctionalgroupswithassociatedacidicprotons.
Figure3.11Representativefunctionalgroupswithadjacentacidicprotons.
Scheme3.8Resonancecapabilitiesofcarboxylicacidscomparedtoalcohols.
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Figure3.12CommoncarboxylicacidsandtheirrespectivepKavalues.
Scheme3.9Esterscanbedeprotonatedαtoestercarbonyls.
Scheme3.10Rationalizationoftheacidityofprotonsαtoestercarbonyls.
Scheme3.11Electronwithdrawinggroupsincreaseaciditybyincreasinganionic
stability.
Scheme3.12Electrondonatinggroupsdecreaseaciditybydecreasinganionic
stability.
Figure3.13Commonelectronwithdrawinggroupsandelectrondonatinggroups.
Figure3.14pKavaluesassociatedwithalcoholsincreaseasalkylbranchingincreases.
Scheme3.13Aminesandalcoholscanbothbedeprotonated.
Scheme3.14HydrocarbonscanbedeprotonatedandhavemeasurablepKavalues.
Chapter04
Scheme4.1Generalrepresentationofbasesreactingwithacids.
Figure4.1Commonbasesusedinorganicchemistry.
Scheme4.2Equilibriumbetweenmethylacetateandtriethylamine.
Scheme4.3Equilibriumbetweenmethylacetateandpotassiumtertbutoxide.
Scheme4.4Equilibriumbetweenmethylacetateandphenyllithium.
Scheme4.5Aminebasicityisrelatedtothenitrogenlonepair.
Scheme4.6Alcoholandetheroxygenscanbeprotonated.
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Scheme4.7Carboxylicacidsandesterscanbeprotonated.
Scheme4.8Aldehydesandketonescanbeprotonated.
Scheme4.9Carbonylbasedfunctionalgroupsdelocalizechargesthroughresonance.
Scheme4.10Protonatedcarbonylbasedfunctionalgroupsdelocalizetheirpositive
charges.
Scheme4.11Protonatedcarbonylbasedfunctionalgroupsaresusceptibletoreaction
withnucleophiles.
Figure4.2Representativenucleophilesandtheircorrespondingacidforms.
Figure4.3Relationshipbetweennucleophilicity,electronegativity,andbasicityas
illustratedusingfirstrowelements.
Figure4.4Theorderofincreasingnucleophilicityofhalideionsisinfluencedby
polarizinginfluencessuchassolventeffects.
Figure4.5Solventshellssurroundhardbasesmoreclosely,makingthemlessreactive
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nucleophilescomparedwithsoftbases.
Figure4.6StericeffectscanoverridetheinfluenceofpKavaluesonnucleophilicity.
Scheme4.12Exampleofanucleophilicreaction.
Chapter05
Scheme5.1RepresentationofanSN2reaction.
Figure5.1Enantiomersaremirrorimages,notsuperimposableanddependentuponthe
tetrahedralarrangementofcarbonatomsubstituents.
Scheme5.2MechanisticexplanationofSN2reactions.
Scheme5.3SN2reactionsproceedwhenincomingnucleophilesaremorenucleophilic
thanoutgoingleavinggroups.
Scheme5.4SN2reactionsdonotproceedwhenincomingnucleophilesareless
nucleophilicthanoutgoingleavinggroups.
Figure5.2Chloromethanebearsapartialnegativechargeontheelectronegative
chlorineatomandapartialpositivechargeonthecarbonatom.
Figure5.3Thecarbon–chlorinebondinchloromethaneispolarized.
Scheme5.5Understandingthedirectionofbondpolarityallowsidentificationof
reactionsite,trajectoryofnucleophile,andidentificationoftheleavinggroup.
Scheme5.6StericbulkslowsdownreactionratesforSN2reactions.
Scheme5.7Resonanceformscanbeusedtorationalizethestabilityofcationsadjacent
tositesofbondunsaturation.
Copyright © 2017. John Wiley & Sons, Incorporated. All rights reserved.
Figure5.4Partialchargescanbedelocalizedthroughunsaturatedbonds.
Scheme5.8ComparisonofSN2andSN2′reactionsasexplainedwitharrowpushing.
Scheme5.9CompetingSN2andSN2′reactionmechanismscanleadtoproduct
mixtures.
Chapter06
Scheme6.1TheinitialphaseofanSN1reactioninvolvesdissociationofaleaving
groupfromthestartingmoleculegeneratingacarbocation.
Scheme6.2ThesecondphaseofanSN1reactioninvolvesreactionofacarbocation
withanucleophilegeneratinganewproduct.
Scheme6.3SolvolysisoftertbutylbromideinmethanolproducesMTBEviaanS
mechanism.
Scheme6.4Explanationofthesolvolysisoftertbutylbromideinmethanolusing
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N1
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arrowpushing.
Scheme6.5MethanolwillnotreactwithtertbutylbromideviaanS
N2mechanism.
Figure6.1Fullysubstitutedcarbonatomspresentsubstituentsintetrahedral
arrangements.
Figure6.2sOrbitalsaresphericalandporbitalsareshapedlikehourglasses.
Figure6.3Hybridorbitalsresultfromcombinationsofsandporbitals.
Figure6.4Likesubstituents,lonepairsinfluencemoleculargeometry.
Figure6.5Differentorbitalhybridizationsresultsindifferentmoleculargeometries.
Figure6.6sp2Hybridizedcarbocationspossesstrigonalplanargeometries.
Scheme6.6ThestereochemicalcoursesofSN2reactionsaredefinedbythe
stereochemicalconfigurationofthestartingmaterials—oneproductisformed.
Scheme6.7ThestereochemicalidentitiesofstartingmaterialssubjectedtoSN1
reactionsarelostduetotheplanarityofreactivecarbocations—twoproductsare
formed.
Figure6.7Tertiarycarbocationsaremorestablethansecondarycarbocations,and
secondarycarbocationsaremorestablethanprimarycarbocations.
Figure6.8Hydrogenatomsorbitalscandonateelectrondensitytoadjacentcationic
centersascanheteroatomsbearingloneelectronpairs.
Figure6.9Heteroatomsstabilizecarbocationsbetterthanhyperconjugationeffects.
Figure6.10Allyliccarbocationsaremorestablethansecondarycarbocations.
Copyright © 2017. John Wiley & Sons, Incorporated. All rights reserved.
Figure6.11Tertiarycarbocationsaremorestablethanallyliccarbocations.
Figure6.12Hyperconjugationoccurswhenacarbon–hydrogenbondliesinthesame
planeasacarbocation’svacantporbital.
Figure6.13Hyperconjugationcanbeviewedasformationofa“pseudodouble
bond.”
Scheme6.8Hyperconjugationleadstomigrationofhydrogenatomsthrougha1,2
hydrideshift.
Scheme6.9Rearrangementsvia1,2hydrideshiftsgeneratemorestablecarbocations
fromlessstablecarbocations.
Scheme6.10Thepinacolrearrangement.
Scheme6.11Thepinacolrearrangementproceedsthroughsolvolysismediatedcation
formation.
Scheme6.121,2Hydrideshiftswillnotoccurwhentheproductcationislessstable
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thanthestartingcation.
Scheme6.13Alkylmigrationsoccurwhentheresultingcarbocationismorestablethan
thestartingcarbocation.
Scheme6.14Conclusionofthepinacolrearrangementinvolvesmigrationofthe
positivechargetotheadjacentoxygenatomfollowedbydeprotonation.
Chapter07
Figure7.1Hyperconjugationoccurswhenacarbon–hydrogenbondliesinthesame
planeasacarbocation’svacantporbital.
Figure7.2Hyperconjugationcanbeviewedasformationofa“pseudodoublebond.”
Scheme7.1Dissociationofaprotonthroughhyperconjugationcompletesthefinalstage
ofanE1eliminationmechanism.
Scheme7.2E1mechanismsexplainadditionalproductsobservedduringSN1
reactions.
Scheme7.3Solvolysisof2bromo2,3dimethylpentaneinmethanolleadsto
formationofuptosixdifferentproductsviamultiplemechanisticpathways.
Scheme7.4Generalrepresentationofbases(BorB−)reactingwithacids(HA)
formingconjugatebases(A−).
Scheme7.5Formationoftheconjugatebaseandassociatedresonancestructure
resultingfromthereactionof2iodomethyldimethylmalonatewithsodiumhydride.
Scheme7.6βEliminationoftheiodidecompletestheE1cBmechanismconvertingthe
2iodomethyldimethylmalonateanionto2methylidenedimethylmalonate.
Copyright © 2017. John Wiley & Sons, Incorporated. All rights reserved.
Scheme7.7Reactionof2iodomethyldimethylmalonatewithanucleophileresultsin
predominantformationoftheE1cBeliminationproduct.
Scheme7.8SN2substitutionreactionscanoccurincompetitionwithE2elimination
reactions.
Figure7.3Tertiarycarbocationsaremorestablethansecondarycarbocations,and
secondarycarbocationsaremorestablethanprimarycarbocations.
Figure7.4Whenacarbon–hydrogen(orcarbonalkyl)bondisalignedwithanempty
porbital,1,2hydride/alkylshiftsandE1eliminationsarefavorable.
Figure7.5Whenacarbon–hydrogenbondoranegativelychargedorbitalisaligned
transperiplanarwithacarbonleavinggroupbond,E2eliminationsandE1cB
eliminationsarefavorable.
Scheme7.9E2eliminationsdependuponthepresenceoftransperiplanar
relationships.
Scheme7.10MechanisticprogressionofE2eliminations.
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Scheme7.11Iftransperiplanarrelationshipscanbeestablished,E2elimination
productscanform.
Chapter08
Scheme8.1Additionofbrominetoethylene.
Scheme8.2Molecularbrominereactswithdoublebondsgeneratingabromoniumion
andabromideanion.
Scheme8.3Bromoniumionspossesselectrophiliccarbonatoms.
Scheme8.4Nucleophilicreactionbetweenabromideanionandabromoniumion
generates1,2dibromoalkanes.
Scheme8.5Proticacidscanaddacrossdoublebonds.
Scheme8.6Doublebondscanbecomeprotonatedunderacidicconditions.
Scheme8.7Nucleophilesaddtoprotonatedolefins.
Scheme8.8Multiplepotentialproductsarepossiblefromadditionofproticacids
acrossdoublebonds.
Scheme8.9Protonationofpropeneintroducescationiccharactertobothprimaryand
secondarycenters.
Figure8.1Whileunsubstitutedolefinsarenonpolar,carbonylsarepolar.
Scheme8.10Nucleophilescanaddtocarbonylstoformalcohols.
Scheme8.11Additionofnucleophilestocarbonylscanbereversible.
Scheme8.12Productsresultingfromadditionofnucleophilestoacetone.
Copyright © 2017. John Wiley & Sons, Incorporated. All rights reserved.
Scheme8.13Carbonylscanbecomeprotonated.
Scheme8.14Additionofnucleophilestocarbonylscanoccurunderacidicconditions.
Scheme8.15Additionofnucleophilestosimplecarbonylsresultsin1,2additions.
Figure8.2ComparisonofSN2andSN2′reactionsasexplainedwitharrowpushing.
Scheme8.16Additionofnucleophilestoα,βunsaturatedcarbonylgroupsas
explainedusingarrowpushing.
Scheme8.17Additionofnucleophilestoα,βunsaturatedcarbonylscanresultin1,4
additions.
Scheme8.18α,βUnsaturatedcarbonylsystemscanbesequentiallysubjectedto1,4
additionsand1,2additions.
Figure8.3Unlikemostcarbonylbasedfunctionalgroups,nonconjugatedesterscan
reactwithnucleophilesandretainthecarbonylunit.
Scheme8.19Theaddition–eliminationmechanismillustratedwitharrowpushing.
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