Chemistry 2100

Lecture 6

Carboxyl DerivativesIn this chapter, we study three classes of compounds derived from carboxylic acids; anhydrides, esters, and amides.– Each is related to a carboxyl group by loss of H2O.

RCOHO

RCOR'O

RCOCR'O O

RCNH2

O

RC-OHO

H-OCR'O

RC-OHO

H-OR' RC-OHO

H-NH2

A carboxylic acid An esterAn anhydride An amide

-H2O -H2O -H2O

acyl

[ acetyl = Ac: R = CH3 ]

NR2

OR'

ClOH carboxylic acid

acid chlorideanhydrideesteramide

Y = O CO R'

O

CR Y

EstersThe functional group of an esterester is a carbonyl group bonded to an -OR group. R may be alkyl or aryl.– Both IUPAC and common names of esters are

derived from the names of the parent carboxylic acids.

– Name the alkyl or aryl group bonded to oxygen first, followed by the name of the acid; replace the suffix -icic acidacid by -ateate.

– A cyclic ester is called a lactonelactone.

Ethyl ethanoate(Ethyl acetate)

Diethyl pentanedioate(Diethyl glutarate)

CH3COCH2CH3 O O

OO

O

O

A five-memberedlactone

O

O

CR Y

+ YH

O

CR Z

+ H Z

O

CR Y

+ YH

O

CR Z

+ H Z

O

CR Y

+ YH

O

CR Z

+ H Z

O

CR Y

+ YH

O

CR Z

+ H Z

O

CR Y

+ YH

O

CR Z

+ H Z

OR'

O

CR Y

+ YH

O

CR Z

+ H ZOR'

OR'

O

CR Y

+ YH

O

CR Z

+ H ZOR'

OR'

OH

O

CR Y

+ YH

O

CR Z

+ H ZOR'

OR'

OH

OH

Fischer esterification O

CR Y

+ YH

O

CR Z

+ H ZOR'

OR'

OH

OH

H+

Hydrolysis of Esters

CH3COCH2CH3

O

H2OH+

CH3COHO

CH3CH2OH+ +

Ethyl acetate Acetic acid Ethanol

Saponification

CH3COCH2CH3

ONaOH

H2OCH3CO-Na+

O

CH3CH2OH

Sodiumhydroxide

+ +

Ethyl acetate Sodiumacetate

Ethanolheat

Properties of Esters

octyl acetate orangeethyl butyrate pineapple

methyl anthranilate grape

coumarin clover methyl salicylate wintergreen

OH

methyl anthranilate grape

C OCH3

O

NH2 NH2

O

O

C

C

C

O

O

O

CH2

CH

CH2

O

(oleic)

(linoleic)

(myristic)

Triglycerides & Waxess

waxes

Reaction with Amines• Esters react with ammonia and with

1° and 2° amines to form amides.

OCH2CH3

O

+ NH3 NH2

O

+ CH3CH2OH

Ethyl 2-phenyl acetate 2-Phenylacetamide

AmidesThe functional group of an amideamide is a

carbonyl group bonded to a nitrogen atom.– To name an amide, drop the suffix -oic acidoic acid

from the IUPAC name of the parent acid, or -ic acidic acid from its common name, and add -amideamide.

– If the amide nitrogen is also bonded to an alkyl or aryl group, name the group and show its location on nitrogen by N- ; two alkyl or aryl groups by N,N-di-.CH3CNH2

OCH3CNHCH3

OHCN(CH3)2

O

N-Methylacetamide(a 2° amide)

Acetamide(a 1° amide)

N,N-Dimethylformamide(a 3° amide)

•• ••

R'

R"

C N

O

R• •

••

••

• •

R'

R"

C N

O

R

•• ••

R'

R"

C N

O

R• •

••

••

• •

R'

R"

C N

O

R

•• ••

R'

R"

C N

O

R• •

••

••

• •

R'

R"

C N

O

R

•• ••

R'

R"

C N

O

R• •

••

••

• •

R'

R"

C N

O

R

•• ••

R'

R"

C N

O

R• •

••

••

• •

R'

R"

C N

O

R

AmidesA cyclic amide is called a lactamlactam.

– The penicillins are referred to as -lactam antibiotics.

O

NH

O

NH

A four-membered lactam(a -lactam)

A seven-membered lactam

N

CH3

NH2

OHO

NHO

S

CH3

COOH

The penicillinsdiffer in the groupbonded to thecarbonyl carbon

The-lactam ring

Amoxicillin

Preparation of Amides• In principle, we can form an amide by

treating a carboxylic acid with an amine and removing -OH from the acid and an -H from the amine.– In practice what occurs if the two are

mixed is an acid-base reaction to form an ammonium salt.

– If this salt is heated to a high enough temperature, water is eliminated and an amide forms.

H2OCH3C-NHCH2CH3

O

CH3C-O- H3NCH2CH3

OH2NCH2CH3CH3C-OH

O+

Aceticacid

Ethanamine(Ethylamine)

An ammonium salt

heat +

An amide

+

Preparation of Amides

• It is much more common, however, to prepare amides by treating an anhydride with an amine.

CH3C-O-CCH3

O OH2NCH2CH3 CH3C-NHCH2CH3

OCH3COH

O+ +

Acetic anhdyride An amide

Anhydrides

The functional group of an anhydrideanhydride is two carbonyl groups bonded to the same oxygen.– The anhydride may be symmetrical (from

two identical acyl groups), or mixed (from two different acyl groups).

– To name an anhydride, drop the word "acidacid" from the name of the carboxylic acid from which the anhydride is derived and add the word "anhydrideanhydride”.

Acetic anhydrideCH3C-O-CCH3

O O

Reaction with Alcohols

Anhydrides react with alcohols and phenols to give an ester and a carboxylic acid.

Aspirin is prepared by the reaction of salicylic acid with acetic anhydride.

CH3COCCH3

O OHOCH2CH3 CH3COCH2CH3 HOCCH3

O+ +

Acetic anhydride Ethyl acetate Acetic acidEthanol

O

COOH

OH CH3C-O-CCH3

OCOOH

OCCH3

O

CH3C-OH

Acetic anhydride

Acetylsalicylic acid(Aspirin)

Salicylic acid

+

Acetic acid

+O O

Phosphoric AnhydridesThe functional group of a phosphoric phosphoric

anhydrideanhydride is two phosphoryl (P=O) groups bonded to the same oxygen atom.

HO-P-O-P-OHOH OH

O O

O-

-O-P-O-P-O-O O

O-

OH OH

HO-P-O-P-O-P-OH

OH

O O O-O-P-O-P-O-P-O-

O O O

O- O- O-

Triphosphoric acid

Diphosphate ion(Pyrophosphate ion)

Diphosphoric acid(Pyrophosphoric acid)

Triphosphate ion

ATP

Adenosine Triphosphate

PolyamidesNylon-66Nylon-66 was the first purely synthetic fiber.– It is synthesized from two six-carbon

monomers.

-H2O+

Hexanedioic acid(Adipic acid)

1,6-Hexanediamine(Hexamethylenediamine)

heat

n

Nylon-66(a polyamide)

O

HOOH

O

NN

ON

ON

H

HH

Hremove H2O

H

H

PolyamidesThe polyaromatic amide known as KevlarKevlar is made from an aromatic dicarboxylic acid and an aromatic diamine.

COHnHOCO O

N NH

HH

H

NHCNHCO O

-H2O

1,4-Benzenediamine(p-Phenylenediamine)

1,4-Benzenedicarboxylicacid

(Terephthalic acid)

nKevlar

(a polyaromatic amide)

+ heat

remove H2O

PolyestersThe first polyester involved polymerization of this diester and diol.

OCH3

OCH3O

O HO

OH

O

O

OO

-CH3OH

Poly(ethylene terephthalate)(Dacron, Mylar)

heat

n

1,2-Ethanediol(Ethylene glycol)

Dimethyl terephthalate

+

remove CH3OH

PolycarbonatesLexan, the most familiar polycarbonatepolycarbonate, is formed by reaction between the disodium salt of bisphenol A and phosgene.

+Na-O

CH3

CH3

O-Na+ Cl Cl

O

OCH3

CH3

O

O

-NaCl

Phosgene

+

Disodium salt of Bisphenol A

Lexan(a polycarbonate)

n

remove Na+Cl-