Carboxylic acids and derivatives
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Carboxylic acids and derivatives

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Carboxylic acids and derivatives




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Presentation on theme: "Carboxylic acids and derivatives"— Presentation transcript:

Slide1

Carboxylic acids and derivatives

Dr.

Sheppard

CHEM

2412

Summer 2015

Klein (2

nd

ed

.)

sections: 21.1, 21.2, 21.6, 21.3, 21.15,

21.4, 21.5, 21.10, 21.7, 21.8,

21.9, 21.11, 21.12, 21.13, 21.14

Slide2

Carboxylic Acids and Derivatives

Carboxylic acidsFound in natureCarboxylic acid derivatives:

Slide3

Carboxylic Acids and Derivatives

Nomenclature Review

Physical Properties

Acidity of Carboxylic Acids

Spectroscopy

Preparation of Carboxylic Acids

Reactions of Carboxylic Acids

Nucleophilic Acyl Substitution

Slide4

I. Nomenclature (Review)

Carboxylic acidsParent chain contains carbon of –CO2HSuffix is “-oic acid”–CO2H is carbon 1Cyclic molecules with –CO2H substituents–CO2H is bonded to carbon 1 of ringAdd “carboxylic acid” to end of ring parent name

Slide5

Examples

StructureName

Slide6

Naming Acid Chlorides

Name corresponding carboxylic acidChange “-ic acid” to “-yl chloride”Examples:

StructureName

Slide7

Naming Acid Anhydrides

If R = R’, name carboxylic acid RCO2H. Replace “acid” with “anhydride”If R ≠ R’, list the two acids alphabetically and add the word “anhydride”Examples:

StructureName

Slide8

Naming Esters

Name alkyl group bonded to oxygen (R’)Name carboxylic acid RCO2HChange “-ic acid” to “-ate”Examples:

StructureName

Slide9

Naming Amides

Name corresponding carboxylic acidChange “-oic acid” to “-amide”Examples:

StructureName

Slide10

Naming Nitriles

Two methodsNitrile carbon is carbon 1 of parent chain. Add “-nitrile” to end of alkane name.Name as carboxylic acid derivative. Replace “-ic acid” with “-onitrile”

Slide11

II. Physical Properties

Carboxylic acids form a hydrogen bond dimerBoiling pointsCarboxylic acids are very highCA > alcohols > aldehyde/ketones > hydrocarbonsCarboxylic acid derivatives are less predictableGenerally amides > carboxylic acids > acid halides/estersTertiary amides < primary and secondary amidesno H-bonding in liquid phase (neat)

Slide12

II. Physical Properties

Solubility in waterLow MW CAs and CADs are solubleSolubility decrease as MW increasesSalts of carboxylic acids are more solubleCADs also react with water (to form carboxylic acids)OdorEsters = sweet or floralCarboxylic acids = unpleasant

Slide13

III. Acidity of Carboxylic Acids

Weak acids (pKa ~ 4-5)Stronger than alcohols because conjugate base is resonance-stabilized

Slide14

III. Acidity of Carboxylic Acids

Conjugate base can be further stabilized if electronegative atom is presentInductive effectPosition of en atom affects pKa

Slide15

III. Acidity of Carboxylic Acids

Substituted benzoic acidsIf Z = electron-donating group, acid is weakerIf Z = electron-withdrawing group, acid is stronger

Slide16

IV. Spectroscopy of CAs: IR

Absorption at 2500-3300 cm-1 for COOH Absorption at 1710-1760 cm-1 for C=O

Slide17

13

C-NMR: 1H-NMR: COOH signal d11-12

IV. Spectroscopy of CAs: NMR

Slide18

IV. Spectroscopy of CADs: IR

Absorption at 1650-1820 cm-1 for C=O

Slide19

13C-NMR:Carbonyl carbon slightly upfield from aldehydes and ketones 1H-NMR: H adjacent to C=O around d2, but doesn’t always help you determine functional groupLook for OH (CA), NH (amide), or OR (ester)

IV. Spectroscopy of CADs: NMR

Slide20

V. Preparation of Carboxylic Acids

Oxidation of primary alcohols and aldehydes (section 13.10)

Slide21

V. Preparation of Carboxylic Acids

Oxidative cleavage of alkenes or alkynes (section 10.9)

Slide22

V. Preparation of Carboxylic Acids

Oxidation of alkylbenzenesWe will see this in the aromatic chapters

Slide23

V. Preparation of Carboxylic Acids

Hydrolysis of nitrilesRequires aqueous acid and heat

Slide24

V. Preparation of Carboxylic Acids

Carboxylation of Grignard reagentsAddition of CO2, followed by H3O+Mechanism:Example:

Slide25

Show two methods that could be used to make butanoic acid from 1-bromopropane

Slide26

VI. Reactions of Carboxylic Acids

Types of reactionsDeprotonationa-SubstitutionOxidation?Reduction?Conversion to CADs

Slide27

Reduction

Need a strong reducing agentLAHReduce to primary alcoholRemember reducing agent chart from alcohol chapter

Slide28

Conversion to CADs

Fischer esterificationCarboxylic acid + alcohol → ester + waterNeeds acid catalyst (H2SO4 or HCl)Reaction is reversiblePush to the right with excess alcohol or remove water

Slide29

Conversion to CADs

Formation of acid chloridesReagent = SOCl2Where have we seen this reagent before?

Slide30

Conversion to CADs

Formation of acid anhydridesAnhydride = without waterApply heat to carboxylic acids to remove water

Slide31

Conversion to CADs

Formation of amidesReaction is difficult with N nucleophile because the N (base) reacts with the carboxylic acid (acid)

Slide32

VII. Nucleophilic Acyl Substitution

Include all of the CA → CAD reactionsAlso used to make CAs from CADs and convert between CADsZ is leaving groupCompare to nucleophilic addition (aldehydes/ketones)

Slide33

VII. Nucleophilic Acyl Substitution

MechanismAcid or base catalyst typically neededAcid makes electrophile more electrophilicBase makes nucleophile more nucleophilic

Slide34

VII. Nucleophilic Acyl Substitution

Reactivity:Less substituted molecules are more reactive

Slide35

VII. Nucleophilic Acyl Substitution

Reactivity:Molecules with better leaving groups are more reactiveLess reactive compounds need heat or catalyst to react and are limited in the number of reactions they will undergo Example: amides only undergo hydrolysis and reduction

Slide36

VII. Nucleophilic Acyl Substitution

Reactivity:More reactive compounds can be converted to less reactive compoundsCan an ester be converted into an amide?Can an amide be converted into an ester?

Slide37

VII. Nucleophilic Acyl Substitution

Types of reactions

Slide38

VII. Nucleophilic Acyl Substitution

Types of reactions:

Reaction

Nucleophile

Product

Special Notes

Hydrolysis

H

2

O

Carboxylic acid

Alcoholysis

ROH

Ester

Aminolysis

NH

3

1° amine

2° amine

1

° amide

2

° amide

3

°

amide

With acid chlorides, 2 eq. of amine are needed:

the nucleophile

neutralizes

HCl

byproduct

Reduction

Hydride from LAH

CA

→ 1° ROH

Ester

→ 1° ROH

Anhydride

→ 1° ROH

Acid chloride → 1° ROH

Amides → amines

Reduction

Hydride

from

DIBALH

aldehyde

Ester only

Grignard

RMgX

3

° alcohol

Ester and acid halide only

Slide39

VII. Nucleophilic Acyl Substitution

Summary of reactions: acid halide

Also GrignardAnhydride formation:

Slide40

VII. Nucleophilic Acyl Substitution

Summary of reactions: anhydridesExample: commercial preparation of aspirin

Slide41

VII. Nucleophilic Acyl Substitution

Summary of reactions: estersHydrolysisAlcoholysisAminolysisReduction (to 1° alcohols and aldehydes)GrignardAlcoholysis of esters = transesterification

Slide42

VII. Nucleophilic Acyl Substitution

Summary of reactions: amidesHydrolysisAcid or base catalystHeatReduction

Slide43

VII. Nucleophilic Acyl Substitution

Summary of reactions: nitrilesHydrolysisAcid or base catalystHeatReduction

Slide44

VII. Nucleophilic Acyl Substitution

Complete the chart with the functional group that will form from the following reactions.

 

H

2

O

ROH

NH

3

LAH

Grignard

Carboxylic acid

 

 

 

 

 

Acid halide

 

 

 

 

 

Acid anhydride

 

 

 

 

 

Ester

 

 

 

 

 

Amide

 

 

 

 

 

Nitrile

Slide45

VII. Nucleophilic Acyl Substitution

Specific reactions:Saponification (soap-making)Hydrolysis of ester in baseIrreversible reaction

Slide46

VII. Nucleophilic Acyl Substitution

Condensation polymerizationA step-growth reactionExample: polyamideWhat is a polyester? How could a polyester be synthesized?

Slide47

VII. Nucleophilic Acyl Substitution

Step-growth polymerizationCompare Fischer esterification……to polymerization

Slide48

VII. Nucleophilic Acyl Substitution

Step-growth polymerizationBiodegradable polymers

Slide49

What is the order of decreasing activity (most reactive = 1, least reactive = 4) toward nucleophilic acyl substitution for the following carboxylic acid derivatives?

Slide50

Draw the products of these reactions.

Slide51

Synthesis

Propose a synthesis for ethyl acetate from ethanol.

Slide52

Provide reagents to complete the reaction scheme

Slide53

Provide reagents for the following reactions: