Chemistry 2100 Chapter 19
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Chemistry 2100
Chapter 19
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 ester 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 -ic acid by -ate.
– A cyclic ester is called a lactone.
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
CH 2
CH
CH 2
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 amide is a
carbonyl group bonded to a nitrogen atom.– To name an amide, drop the suffix -oic acid
from the IUPAC name of the parent acid, or -ic acid from its common name, and add -amide.
– 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 lactam.
– The penicillins are referred to as b-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 anhydride 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 "acid" from the name of the carboxylic acid from which the anhydride is derived and add the word "anhydride”.
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
anhydride 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-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 Kevlar 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 polycarbonate, 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-
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