Chapter 17 Carbonyl Alpha-Substitution and Condensation Reactions
Solutions to Problems Condensation Reactions II, Building Bridges to Knowledge
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Transcript of Solutions to Problems Condensation Reactions II, Building Bridges to Knowledge
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SolutiontoProblemsCondensationReactionII
BuildingBridgestoKnowledge
Photo by Michaelle Cadet
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1. Suggestnamesforeachofthefollowing.
(a)
ethyl2-[2-oxocyclohexyl]propanoate (b)
methyl2,2-diphenylacetate (c)
diethyladipate (d)
n-propylpentanoate
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2. SuggestIUPACnamesforthefollowingstructures.
(a) ethylcyclobutanecarboxylate
n-propyl3-methylbutyrate
3-ethyl-2-pentanone
methyl4-oxo-2-methylpentanoate
isopropyl4-hydroxyoctanoate
(3) Suggestsynthesesfor (a)
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(b)
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4. Suggestamechanismforthefollowingreaction.
5. Suggestamechanismforthefollowingobservation.
(1)
(2)
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6. Suggestasynthesisfor2-methylcyclopentanonefromadipicacidandanyothernecessaryorganicorinorganicmaterials.
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7. Suggestasynthesisfor2-methyl-4-pentenoicacidfromdiethylmalonateandanynecessaryorganicandinorganicmaterials.Ifthediethylmalonateisde-esterfied,acidified,anddecarboxylated,theremainingchemicalentityinscribedinasquarewouldbe
2-methyl-4-pentenoicacid
Therefore,thesynthesiscouldbeaccomplishedusingthefollowingsequenceofreactions:
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8. AcompoundwiththemolecularformulaofC12H14O3,exhibitsthefollowing
1HNMRand13CNMRspectra.
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TheinfraredspectrumofC12H14O3exhibitsprominenttransmittancesignalsat1724cm-1;1751cm-1;1250cm-1;and1051cm1.C12H14O3isinsolubleinwater,diluteacid,ordilutebase,anddoesnotreactwithacetylchloride,butitdoesreactwith2,4-dinitrophenylhydrazine.Also,C12H14O3reactswithhotsodiumhydroxide,followedbyacidhydrolysis,andheattoproduceacolorlessgas,andC9H10O.C9H10O,aneutralcompound,isapaleyellowliquidthatisinsolubleinwater,andgivesanegativeiodoformtest,butreactswith2,4-dinitrophenylhydrazine.C9H10OreactswithlithiumaluminumhydridefollowedbyhydrolysistoproduceC9H12O.C9H12OreactswithacetylchloridetogiveC11H14O2.FollowingaretheNMRspectrumandpartialmassspectrumofC9H10O.
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Prominentsignalsatm/eequalto105and57arenotshowninthemassspectrumofC9H10O.C9H12OExhibitsastronginfraredtransmittancesignalat3333cm-1,anditdoesnotproduceayellowprecipitatewhentreatedwithsodiumhydroxideiniodine.
(a) SuggeststructuralformulasforC12H14O3,C9H10O,C9H12O, andC11H14O2.
C12H14O3
C9H10O
C9H12O
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C11H14O2
(b) Writeamechanismtoaccountfortheformationofthecolorlessgas.
Carbondioxide,CO2isthecolorlessgas.
(c)GiverationalreasonsforthesolubilityobservationsforC12H14O3
C12H14O3isanester;therefore,itisinsolubleinwater,acidorbase.
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(d) WriteanequationforthereactionofC12H14O3with2,4-
dinitrophenylhydrazine.
(e) WriteareactionbetweenC9H12Oandacetylchloride.
(f) WhatistheIUPACnameforC12H14O3?
ethyl2-methyl-3-phenylpropan-3-onoate
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(g)SuggestasynthesisforC12H14O3
8. Suggeststructuresconsistentwiththedataprovidedinthefollowingreactions,andsuggestmechanismstoaccountfortheirformations.
(a)
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Mechanism (1)
(2)
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(b)
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WhatistheIUPACnameforC4H6O3?
2,4-dioxopentanoicacid
10. C8H12O4,canbesynthesizedfromethylacetoacetateviathefollowingsteps.
Step1 Ethylacetoacetate+sodiumethoxide/ethanol Step2
Theproductofstep1reactswithmethylbromidetoform C7H12O3
Step3 Theproductofstep2reactswithsodiumethoxide/ethanol
Step4
Theproductofstep3reactswithmethylbromidetoproduce C8H14O3 Step5 Theproductofstep4reactswithzincandbromoaceticacid followedbyhydroylsisinanacidicmediumtoformC12H22O5. TreatingC12H22O5withexcesshydrochloricacidandheat producedC8H12O4.SuggestastructuralformulaforC8H12O4.
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11. Therearemanyexamplesofdecarboxylationinbiologicsystems.Forexample,innature,isopentenylpyrophosphate,abiologicalprecursortosqualeneandcholesterol,isformedfrom3-phosphate-5-pyrophosphatemevalonicacidviathefollowingchemicalequation.
Writeamechanismfortheconversionof3-phosphate-5-pyrophosphatemevalonicacidtoisopentenylpyrophosphate,andidentifytheotherproductsproducedinthetransformation.
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12. Suggestasynthesisfor6-methyl-5-hepten-2-onefromethyl4-oxopentanoateandanyothernecessaryorganicorinorganicreagents.
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13. Thecarbon-13magneticresonancespectrumandtheprotonmagneticresonancespectrumofanunknowncompoundwiththemolecularformulaofC6H10O3arerespectivelyrepresentedbelow.
SuggestastructureforC6H10O3.
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14. Suggestasynthesisforyouranswertoproblem13fromanyorganicandinorganicmaterials.
15.Suggestamechanismtoexplainthefollowingconversion.
A
A
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16. YotesandAndersonreportedthefollowingtransformationintheJournaloftheAmericanChemicalSociety.
Suggestaseriesofelementarystepsthatcouldaccount forthistransformation.Inyoursuggestedmechanism,usearrowstoshowhowelectronsareflowing.
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(1)
(2)
(3)
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(4)
Acidification
17.Aperplexedundergraduatesummerresearchstudentwasgivenanassignmentbyhisprofessortomakeethyl3-hydroxy-3-methylbutanoate.Hedecidestotreatmethylmagnesiumiodidewithethylacetoacetateinanefforttoobtainethyl3-hydroxy-3-methylbutanoate.Everythingappearedtohavegonewell.Thereactionmixturebubbled,andheproceededwithcareandgreatskill.Heisolatedanexcellentyield,butuponspectralanalyseshedeterminedthatethylacetoacetate(thestartingmaterial)wastheonly
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product.Heimmediatelydiscardedtheproduct,and,intears,rantohisprofessor’soffice.(a) Writeanequationtodemonstratewhatwentwrongwiththisstudent’s
research(don’tforgetthegenerationofbubbles).
(b) Suggestamoreacceptablepathwaythatcouldleadtoformationofthedesiredproduct,ethyl3-hydroxy-3-methylbutanoate.
18.Suggestlaboratorysynthesesforthefollowingcompounds:
(a)
andanyotherorganicandinorganicreagents
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AcidCatalyzedDehydrationandDe-esterification
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(b)
Fromdiethylphthalateanddiethylmalonateandanyotherinorganicmaterials.
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(c)
fromadipicacidandanyothernecessaryorganicorinorganicmaterials.
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19.(a) Suggestasynthesisfor2,7-octanedionefrom1,2-dimethylcyclohexeneand
anyothernecessaryorganicandinorganiccompounds
(b) When2,7-octanedioneistreatedwithsodiumethoxideandthenacidified,
compoundAisisolated.
CompoundA,methyl(2-methylcyclopentenyl)ketone
Suggestamechanismthatwouldaccountfortheconversionof2,7-octanedioneintocompoundA.
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(1)
(2)
(3)
AcidCatalyzedDehydration (1)
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(2)
(3)
20.
α-Onocerin(I)hasbeensynthesizedinseverallaboratories.Approximatelyfivedecadesago,Storketal.publishedatwenty-onestepsynthesisforα-onocerin.Fourdecadeslater,E.J.Coreyetal.atHarvardUniversitypublishedafourstepsynthesisforα-onocerinstartingwithatriterpenederivative.
I
Storkandhisresearchteamdecidedtouse6-methoxytetrahydroteralone(3,4-dihydro-6-methoxy-1(2H)-naphthalenone),compoundII,astheprecursorforthesynthesisofcompoundI.
II
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ThefirstfewstepsintheirlongsynthesisaredesignedtopreparecompoundIII.
III
Thefollowingreagents(notnecessarilyinreactionsequence)aswellasotherreagents(notmentioned)canbeusedtopreparecompoundIII:(a) 3-buten-2-one(b) B2H6(c) aGrignardreagentSuggestasynthesisofcompoundIIIfromcompoundIIusingthesethreereagentsandanyothernecessaryreagents.
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CompoundIIIOncecompoundIIIisprepared,potassiumtertiary-butoxideandmethyliodidecanbeusedtoconvertcompoundIIItocompoundIV.
IV
SuggestamechanismtoexplainthetransformationofcompoundIIIintocompoundIVinthepresenceofpotassiumt-butoxideandmethyliodide.
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(1)
(2)
(3)
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(4)
21.
Suggestasynthesisforp-methoxybenzoicacidfromcyclohexaneandanyothernecessaryorganicandinorganicmaterials.
Crackingofcyclohexanetobenzene
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AnetionicequationforthereductionofnitobenzenewithSncouldbewrittenas
AplausiblemechanismforthereductionofnitrobenzenewithTin,Sn,inhydrochloricacidcouldincludethefollowingelementarysteps.
(1)
(2)
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(3)
(4)
(5)
(6)
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(7)
(8)
(9)
(10)
(11)
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(12)
(13)
(14)
(15)
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Thesumofsteps1-15wouldgive
Formationofthediazoniumsalt
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