[PDF] CARBOXYLIC ACIDS Substituent Effects on the Acidity

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CARBOXYLIC ACIDS

1

Carboxylic Acids

Introduction

2 attachedtothecarbonyl(C=O)group.

Natural Carboxylic Acids

3 milkgenerallyhavesharpflavours.

Nomenclature of Carboxylic Acids

4 thecarboxylicacid.

Structure of AcidNaturalSource Common

Name

Ants (Formica)Formic acid

Vinegar (Acetum)Acetic acid

BasicFat (Propio)Propionicacid

Rancid butter (Butyrum)Butyric acid

Presentin aValerianherbValericacid

Goat (Caper)Caproicacid

HCOH

OCH3COH

O

CH3CH2COH

O

CH3CH2CH2COH

O

CH3CH2CH2CH2CH2COH

O

Common Names of Carboxylic Acids

5 lengthofthecarboxylicacid. # of CarbonsPrefixCommon Name of Acid

1Form-Formic acid

2Acet-Acetic acid

3Propion-Propionicacid

4Butyr-Butyric acid

5Valer-Valeric acid

6Capro-Caproicacid

Aromatic acidBenzo-Benzoic acid

IUPAC Nomenclature of Aliphatic Carboxylic

Acids 6 # of CarbonsStructure & IUPAC

Name ofAlkane

Structure & IUPAC

Name of Acid

1

MethaneMethanoicacid

2

EthaneEthanoicacid

3

PropanePropanoicacid

HCH H H HCOH

OCH3CH3CH3COH

O

CH3CH2CH3CH3CH2COH

O

Systematic Nomenclature of Substituted

Carboxylic Acids

8 arederivedby: all,thecarboxylgroups. groupi.ethecarboxylcarbonisC-1. numberingintheparentchain. acid.

Systematic Nomenclature of Substituted

Carboxylic Acids

9

Example

usingthesamesequence.

Systematic Nomenclature of Cyclic

Carboxylic Acids

10 cycloalkeneorarene. takentobeattachedtoC-1ofthering. CO2H

Cyclohexanecarboxylic acid

CHO

Cyclohexanecarbaldehyde

Na2Cr2O7

H2SO4

Systematic Nomenclature of Substituted

Cyclic Carboxylic Acids

11 toC-1ofthering. namedasbenzenecarboxylicacid.

IUPAC Nomenclature of Substituted

Aromatic Carboxylic Acids

12

Systematic Nomenclature of Dicarboxylic

Acids 13 parenthydrocarboni.e.alkanedioicacid.

Systematic NameCommonNameStructure

EthanedioicacidOxalic acidHO2C-CO2H

PropanedioicacidMalonicacidHO2CCH2CO2H

HexanedioicacidAdipicacidHO2C(CH2)4CO2H

Systematic Nomenclature of Substituted

DicarboxylicAcids

14 by: thenameoftheparenthydrocarbon. nameofthedicarboxylicacid.

Systematic Nomenclature of Cyclic

DicarboxylicAcids

15 isomers.

Properties of Carboxylic Acids

16

Acidity of Carboxylic Acids

18 hydrogenion(proton).

Substituent Effects on the Acidity of

Aliphatic Carboxylic Acids

19 acidityofthecarboxylicacid.

ALKYL GROUPS:EFFECTS OF ELECTRON-DONATING GROUPS

Name of AcidStructurepKaEffect

MethanoicacidHCO2H3.8

EthanoicacidCH3CO2H4.7Weakeningacidity

PropanoicacidCH3CH2CO2H4.9Negligible effect

HeptanoicacidCH3(CH2)5CO2H4.9

Substituent Effects on the Acidity of

Aliphatic Carboxylic Acids

20

ELECTRON WITHDRAWING GROUPS

Name of AcidStructurepKaEffect

EthanoicacidCH3CO2H4.7

MethoxyethanoicacidCH3OCH2CO2H3.6

acidityCyanoethanoicacidNC-CH2CO2H 2.5

NitroethanoicacidO2N-CH2CO2H 1.7

withdrawinggroups.

Substituent Effects on the Acidity of

Aliphatic Carboxylic Acids

21
carboxylateanion. -HALOGENS: EFFECT OF ELECTRONEGATIVITY ON ACIDITY

Name of AcidStructurepKaEffect

EthanoicacidCH3CO2H4.7

aciditywithincreasing electronegativity

ChloroethanoicacidClCH2CO2H2.9

BromoethanoicacidBrCH2CO2H 2.9

Substituent Effects on the Acidity of

Aliphatic Carboxylic Acids

22
anionandthehighertheiracidities.

CUMMULATIVE EFFECT OF SUBSTITUENTS ON ACIDITY

Name of AcidStructurepKaEffect

additiveDichloroethanoicacidCl2CHCO2H1.3

TrichloroethanoicacidCl3CCO2H 0.9

Substituent Effects on the Acidity of

Aliphatic Carboxylic Acids

23
(numberof-bonds).

EFFECT OF BOND DISTANCE ON ACIDITY

Name of AcidStructurepKaEffect

effectduetothe inductiveeffect decreases rapidlywith distance.

3-Chloropropanoic acidClCH2CH2CO2H4.0

4-Chlorobutanoic acidClCH2CH2CH2CO2H4.5

Acidity of Aromatic Carboxylic Acids

24
throughʌbonds.

Acidity of Aromatic Carboxylic Acids:

Inductive Effect

25
invokedinexplainingitsdegreeofacidity.

Acidity of Aromatic Carboxylic Acids:

Inductive Effect

26
unsubstitutedbenzoicacid. derivatives.

Acidity of Aromatic Carboxylic Acids: the

Resonance Effect

27
thanbenzoicacid. acids.

Resonance Structures of Isomeric

Nitrobenzoates

28
C N C N m-Nitrobenzoic acid p-Nitrobenzoic acid O O C N C NO Resonance Structures of carboxylate anions derived from ionization of isomeric nitrobenzoic acids C NO C NO C NO

OOOOOO

OOOOOOOO

OOOO OOOO C o-Nitrobenzoic acid COOOO NO O NO OCOO NO OCOO NO O

Highly stabilizing

Highly stabilizing

Synthesis of Carboxylic Acids

Oxidation of Primary Alcohols to Carboxylic Acids

31

RCH2OHOxidizing AgentRCO2H

syntheticallyinefficient.

Synthesis of Carboxylic Acids

Oxidation of Primary Alcohols to Carboxylic Acids

32
potassiumpermanganate.

Example

Synthesis of Carboxylic Acids

Oxidation of Aldehydesto Carboxylic Acids

33
employedsuccessfully.

RCHOOxidizing AgentRCO2H

NotethatAg2Odoesnotoxidizealcohols

Synthesis of Carboxylic Acids

Oxidation of Aldehydesto Carboxylic Acids

34
aldehydessuchassilver(I)oxide. carboxylicacid.

Synthesis of Carboxylic Acids

Ozonolysisof Alkenes to Carboxylic Acids

35

Ozonolysisof Alkynes to Carboxylic Acids

36
tocarboxylicacids. relativelypure.

Carboxylationof Grignard Reagents

37
reagent. atomcomplexeswiththeoxygenatom.

Carboxylationof Grignard Reagents

38
carboxylationofGrignardreagents.

Examples

Hydrolysis of Nitriles

39

Example

reactionofcyanideionswithalkylhalides.

Side-Chain Oxidation of Alkylbenzenesto Benzoic

Acids 40

Reactions of Carboxylic Acids

41
(1)Reactions at the acidic hydrogen on the carboxyl group. (2)Reactions at the carbonyl group (3)Reactions at the carboxylateoxygen (4)Reactions that lead to loss of the carboxyl group as CO2 onthecarboxylgroup.

Reaction of Carboxylic Acids with Sodium

Bicarbonate

42

Example

acids. C O OH+C O

O+NaHCO3NaH2O

Benzoic acidSodium benzoate

+CO2

Reactions of Carboxylic Acids with Strong Bases

43

Example

carboxylatesalts.

Mechanism

RC O O+HRC O

O+NaOHNaH2ORC

O

O+OHHRC

O O+HOH C O OH+C O

O+NaOHNaH2O

Benzoic acidSodium benzoate

Reaction of Carboxylic Acids with Diazomethane

44

Example

methylesters.

Mechanism of Esterificationwith Diazomethane

45
group). Step 1:Deprotonation of the acidic proton on the carboxylic acid by diazomethane provides a carboxylate anion and a methyldiazonium ion.

Step 2: Loss of nitrogen

Acid-CatalysedEsterificationof Carboxylic Acids

46
asH2SO4,HClandH3PO4ororganicacidssuchas RC O

OH+R'OHRC

O

OR'+H2OH2SO4

Example

Mechanism of the Acid-CatalysedEsterificationof

Carboxylic Acids

47
carbonylandprotontranfer acid(activationofthecarbonylcarbon). regenerationofacidcatalyst. RC O

OHH+RC

O OH H Acid

Catalyst

Protonated

carboxylic acid

Reaction of Carboxylic Acids with Amines

48
Amines, being organic bases, react with carboxylic acids to form ammonium salts. RC O O+HRC O ONHR' R' NHR' R' H

Ammonium salt

RC O O+HRC O ONHR' R' NHR' R' H

Ammonium salt

Mechanism

Example

C O OH+C O O

Benzoic acid

N Et H Et N Et H Et H

Reaction of Carboxylic Acids with Amines in

Presence of DCC

49
presenceofDCCtoformamides. toaidincouplingtotheaminogroup. +COHR O

1,3-Dicyclohexylcarbodiimide

+C OHNHN

Dicyclohexylurea

(DCHU)

R'NH2CHNR

O +CNN (DCC) R' Amide +DCC+C OHNHN

Dicyclohexylurea

CO2H CH3 NH CH3 N O

N,N-Diethyl-m-toluamide

Mechanism of Coupling Carboxylic Acids with

Amines Using DCC

50
leavinggroup.

CNN+COR

O HCNN H +COR O CNN H +COR OCN N O H CR O CN N O H CR O R'N+ R'N H R O +C OHNN C Oquotesdbs_dbs10.pdfusesText_16

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