Chapter20TheChemistryofCarboxylicAcids

Organic Chemistry, 5th ed. Marc Loudon

Eric J. Kantorowski California Polytechnic State University San Luis Obispo, CA

Chapter20Overview

•  20.1NomenclatureofCarboxylicAcids

•  20.2StructureandPhysicalProper>esofCarboxylicAcids•  20.3SpectroscopyofCarboxylicAcids•  20.4Acid‐BaseProper>esofCarboxylicAcids•  20.5FaEyAcids,Soaps,andDetergents•  20.6SynthesisofCarboxylicAcids•  20.7Introduc>ontoCarboxylicAcidsReac>ons•  20.8ConversionofCarboxylicAcidsintoEsters•  20.9ConversionofCarboxylicAcidsintoAcidChloridesand

Anhydrides

•  20.10Reduc>onofCarboxylicAcidstoPrimaryAlcohols

•  20.11Decarboxyla>onofCarboxylicAcids2

CarboxylicAcids

•  Thecharacteris>cfunc>onalgroupincarboxylicacidsisthecarboxygroup

•  Thischapterwillalsosurveythechemistryofsulfonicacids

320.1NomenclatureofCarboxylicAcids

CommonNomenclature

•  Dicarboxylicacids

420.1NomenclatureofCarboxylicAcids

CommonNomenclature

520.1NomenclatureofCarboxylicAcids

CommonNomenclature

620.1NomenclatureofCarboxylicAcids

Subs>tu>veNomenclature

720.1NomenclatureofCarboxylicAcids

StructureandPhysicalProper>es

•  ThecarbonyloxygenistheoxygeninvolvedwiththeC=Odoublebond

•  ThecarboxylateoxygenistheoxygeninvolvedwiththeC‐Osinglebond

820.2StructureandPhysicalProper?esofCarboxylicAcids

StructureandPhysicalProper>es

•  Manyaroma>canddicarboxylicacidsaresolids

•  Simplecarboxylicacidsanddicarboxylicacidsaresolubleinwater(H‐bonding)

920.2StructureandPhysicalProper?esofCarboxylicAcids

IRSpectroscopy

•  C=Ostretch:1710cm‐1(asthedimer)•  O‐Hstretch:2400‐3600cm‐1(verybroad)

1020.3SpectroscopyofCarboxylicAcids

NMRSpectroscopy

•  O‐H:δ9‐13(broad;exchangeswithD2O)

1120.3SpectroscopyofCarboxylicAcids

AcidityofCarboxylicAcids

•  Acidityisoneofthemostimportantproper>esofcarboxylicacids

•  Conjugatebasesofcarboxylicacidsarecalledcarboxylateions

1220.4Acid‐BaseProper?esofCarboxylicAcids

AcidityofCarboxylicAcids

1320.4Acid‐BaseProper?esofCarboxylicAcids

pKaValuesofSomeCarboxylicAcids

1420.4Acid‐BaseProper?esofCarboxylicAcids

AcidityofSulfonicAcids

•  Sulfonicacidsareusefulasacidcatalystsinorganicsolventsbecausetheyaremoresolublethanmostinorganicacids

1520.4Acid‐BaseProper?esofCarboxylicAcids

AcidityofCarboxylicAcids

•  Thealkalimetalsaltsofcarboxylicacidsaresolubleinwater

•  Evena5%NaHCO3solu>onisbasicenough(pH≈8.5)todissolveacarboxylicacid

1620.4Acid‐BaseProper?esofCarboxylicAcids

BasicityofCarboxylicAcids

•  Thecarbonyloxygenisweaklybasic

•  Notethatthecarboxylateoxygenisnotprotonated

•  Thebasicityofcarboxylicacidsplaysanimportantroleinmanyoftheirreac>ons

1720.4Acid‐BaseProper?esofCarboxylicAcids

FaGyAcids

•  Carboxylicacidswithlong,unbranchedcarbonchains

•  Manyareisolatedfromfatsandoilsbythehydroly>cprocessofsaponifica>on

1820.5FaFyAcids,Soaps,andDetergents

SoapsandDetergents

•  Na+andK+saltsoffaEyacidsaresoaps

•  Soapsarepartofalargerclassofcompoundscalleddetergents

1920.5FaFyAcids,Soaps,andDetergents

Surfactants

•  Soapsanddetergentsarepartofanevenbroaderclassofcompoundscalledsurfactants

•  Surfactantscontainapolarheadgroupandahydrocarbontail

•  Phospholipidsarealsosurfactants

2020.5FaFyAcids,Soaps,andDetergents

Micelles

•  Micellesformwhenthesurfactantconcentra>onisraisedabovethecri>calmicelleconcentra>on

•  Micellesaresphericalaggregatesof50‐150surfactantmolecules

2120.5FaFyAcids,Soaps,andDetergents

SynthesisofCarboxylicAcids

•  Oxida>onofprimaryalcohols•  Side‐chainoxida>onofalkylbenzenes•  Grignardororganolithiumwithcarbondioxide

2220.6SynthesisofCarboxylicAcids

CarboxylicAcidReac>ons

•  Therearefourmaintypesofreac>ons:1.Reac>onsatthecarbonylgroup

2.Reac>onsatthecarboxylateoxygen

3.LossofthecarboxygroupasCO2(decarboxyla>on)

4.Reac>onsinvolvingtheα‐carbon(Ch22)

2320.7Introduc?ontoCarboxylicAcidsReac?ons

CarboxylicAcidReac>ons

•  Reac>onsatthecarbonylgroup

2420.7Introduc?ontoCarboxylicAcidsReac?ons

CarboxylicAcidReac>ons

•  Reac>onsatthecarboxylgroup

2520.7Introduc?ontoCarboxylicAcidsReac?ons

CarboxylicAcidReac>ons

•  LossofthecarboxygroupasCO2(decarboxyla>on)

2620.7Introduc?ontoCarboxylicAcidsReac?ons

Acid‐CatalyzedEsterifica>on

•  Estersarecarboxylicacidderiva>ves

•  AlsoreferredtoastheFischeresterifica>on•  Theequilibriumisfavorable,butnotlarge

•  Thealcoholneedstobepresentinlargeexcess(commonlyasthesolvent)

2720.8ConversionofCarboxylicAcidsintoEsters

Acid‐CatalyzedEsterifica>on

•  Isotopiclabelingwith18Odeterminedthatthecarboxyloxygenintheesterisfromthealcohol

2820.8ConversionofCarboxylicAcidsintoEsters

Acid‐CatalyzedEsterifica>on

2920.8ConversionofCarboxylicAcidsintoEsters

Acid‐CatalyzedEsterifica>on

3020.8ConversionofCarboxylicAcidsintoEsters

•  Esterifica>onillustratesaverygeneralmechanis>cpaEern

•  Comparewithaldehydesandketones

Acid‐CatalyzedEsterifica>on

3120.8ConversionofCarboxylicAcidsintoEsters

Esterifica>onbyAlkyla>on

•  Thecarboxylateoxygenactsasanucleophile

3220.8ConversionofCarboxylicAcidsintoEsters

Esterifica>onbyAlkyla>on

•  Carboxylateionsarelessbasic,andthereforelessnucleophilic,thanalkoxides

•  ThisisanSN2reac>onandworksbestwithespeciallyreac>vealkyla>ngagents

3320.8ConversionofCarboxylicAcidsintoEsters

SynthesisofAcidChlorides

3420.9ConversionofCarboxylicAcidsintoAcidChloridesandAnhydrides

SynthesisofSulfonylChlorides

•  Sulfonylchloridesaretheacidchloridesofsulfonicacids

•  TypicallytheirsodiumsaltsaretreatedwithPCl5

3520.9ConversionofCarboxylicAcidsintoAcidChloridesandAnhydrides

SynthesisofSulfonylChlorides

•  Aroma>csulfonylchloridesmayalsobeprepared

3620.9ConversionofCarboxylicAcidsintoAcidChloridesandAnhydrides

SynthesisofAnhydrides

•  Anhydride=“withoutwater”

3720.9ConversionofCarboxylicAcidsintoAcidChloridesandAnhydrides

SynthesisofAnhydrides

•  Mostanhydridesmaythemselvesbeusedtoformotheranhydrides

3820.9ConversionofCarboxylicAcidsintoAcidChloridesandAnhydrides

SynthesisofAnhydrides

•  5‐and6‐memberedringanhydridescancommonlybeformedsimplybyhea>ng

3920.9ConversionofCarboxylicAcidsintoAcidChloridesandAnhydrides

Reduc>onofCarboxylicAcids

•  ThepowerfulreducingagentLiAlH4isrequired

4020.10Reduc?onofCarboxylicAcidstoPrimaryAlcohols

•  Theoverallsequenceforreduc>onissummarizedas:

Reduc>onofCarboxylicAcids

4120.10Reduc?onofCarboxylicAcidstoPrimaryAlcohols

Decarboxyla>onofCarboxylicAcids

•  Decarboxyla>on:ThelossofCO2fromRCO2H

•  Mostordinarycarboxylicacidsdonotpar>cipate,butthefollowingtypesdo:

1.β‐ketoacids

2.Malonicacidderiva>ves

3.Carbonicacidderiva>ves

4220.11Decarboxyla?onofCarboxylicAcids

Decarboxyla>onofCarboxylicAcids

•  Decarboxyla>onfromβ‐ketoacids

•  Decarboxyla>onoftheβ‐ketoacidoccursmorereadilythanitsconjugatebaseform

4320.11Decarboxyla?onofCarboxylicAcids

Decarboxyla>onofCarboxylicAcids

•  Decarboxyla>onfrommalonicacidderiva>ves

•  Thisreac>onalsodoesnotoccurinbase•  Notethesimilaritytotheβ‐ketoacid

4420.11Decarboxyla?onofCarboxylicAcids

Decarboxyla>onofCarboxylicAcids

•  Decarboxyla>onfromcarbonicacidderiva>ves

4520.11Decarboxyla?onofCarboxylicAcids