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)

6

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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)

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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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