Download Chemistry 2100 - Bonham Chemistry

Chemistry 2100
Lecture 6
Carboxyl Derivatives
In 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.
O
RCOH
A carboxylic acid
O O
RCOCR'
An anhydride
-H2 O
O
O
RC- OH H- OCR'
O
RCOR'
An ester
-H2 O
O
RCNH2
An amide
-H2 O
O
O
RC- OH H- OR' RC- OH H- NH 2
O
R
[
C
Y
acyl
acetyl = Ac: R = CH3 ]
Y =
OH
Cl
O CO R'
O R'
NR2
carboxyl i c aci d
aci d chloride
anhydri de
e ste r
ami de
Esters
The 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.
O
CH3 COCH2 CH3
Ethyl ethanoate
(Ethyl acetate)
O
O
O
O
O
Diethyl pentanedioate
(Diethyl glutarate)
O
A five-membered
lactone
O
R
C
O
Y
+
H Z
R
C
Z
+
H Y
O
R
C
O


Y
+


H Z
R
C
Z
+
H Y
O
R
C
O


Y
+


H Z
R
C
Z
+
H Y
O
R
C
O


Y
+


H Z
R
C
Z
+
H Y
O
R
C
O


Y
+


H Z
R
C
Z
OR'
+
H Y
O
R
C
O


Y
+


H Z
OR'
R
C
Z
OR'
+
H Y
O
R
C
O


OH
Y
+


H Z
OR'
R
C
Z
OR'
+
H Y
O
R
C
O


OH
Y
+


H Z
OR'
R
C
Z
OR'
+
H OH
Y
Fischer esterification
O
R

C
O

OH
Y
+


H Z
OR'
H+
R
C
Z
OR'
+
H OH
Y
Hydrolysis of Esters
O
CH3 COCH2 CH3
Eth yl acetate
+
H2 O
H
+
O
CH3 COH + CH3 CH2 OH
Acetic acid
Ethanol
Saponification
O
H2 O
CH3 COCH2 CH3+ N aOH
heat
Ethyl acetate
Sodium
hydroxide
O
CH3 CO - N a++ CH3 CH2 OH
Sodium
Ethanol
acetate
Properties of Esters
ethyl butyrate
pineapple
octyl acetate
orange
O
C OCH3
OH
coumarin
clover
methyl salicylate
methyl anthranilate
NH
NH22
wintergreen
grape
methyl anthranilate
grape
Triglycerides & Waxess
O
O
CH 2 O
C O CH
(oleic)
CH 2 O
C
O
(myristic)
C
(linoleic)
waxes
Reaction with Amines
• Esters react with ammonia and with 1° and 2°
amines to form amides.
O
O
OCH2 CH3 + N H3
Ethyl 2-phenyl acetate
N H2 + CH3 CH2 OH
2-Phenylacetamide
Amides
The 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-.
O
CH3 CNH2
Acetamide
(a 1° amide)
O
CH3 CNHCH3
N -Methylacetamide
(a 2° amide)
O
HCN(CH3 ) 2
N ,N-D imethylformamide
(a 3° amide)
•• ••
O
R
C
•
•
R'
••
R
N
R"
••
O ••
C
R'
N
R"
•• ••
O
R
C
•
•
R'
••
R
N
R"
••
O ••
C
R'
N
R"
•• ••
O
R
C
•
•
R'
••
R
N
R"
••
O ••
C
R'
N
R"
•• ••
O
R
C
•
•
R'
••
R
N
R"
••
O ••
C
R'
N
R"
•• ••
O
R
C
•
•
R'
••
R
N
R"
••
O ••
C
R'
N
R"
Amides
A cyclic amide is called a lactam.

O
O
b NH
A four-membered lactam
(a b-lactam)
NH
A seven-memb ered lactam
– The penicillins are referred to as b-lactam
antibiotics.
HO
The p enicillins
differ in th e group
bond ed to th e
carbonyl carbon
Theb-lactam rin g
O
N
NH2 H
O
A moxicillin
S
N
CH3
CH3
COOH
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.
O
CH 3 C-OH + H2 NCH2 CH 3
Acetic
Ethanamine
acid
(Ethylamine)
O
+
CH3 C-O H3 NCH2 CH3
An ammonium
s alt
h eat
O
CH 3 C-NHCH2 CH3 + H2 O
An amid e
Preparation of Amides
• It is much more common, however, to
prepare amides by treating an
anhydride with an amine.
O O
CH3 C-O-CCH3 + H2 NCH2 CH3
Acetic anhdyride
O
O
CH3 C-NHCH2 CH3 + CH3 COH
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”.
O O
CH3 C-O-CCH3
Acetic an hydrid e
Reaction with Alcohols
Anhydrides react with alcohols and phenols to
give an ester and a carboxylic acid.
O O
CH3 COCCH3 + HOCH2 CH3
Acetic anhydride Ethanol
O
O
CH3 COCH 2 CH 3 + HOCCH3
Ethyl acetate
Acetic acid
Aspirin is prepared by the reaction of salicylic
acid with acetic anhydride.
COOH
OH
Salicylic acid
+
O
O
CH3 C- O-CCH3
Acetic anhyd rid e
COOH
OCCH 3
O
Acetylsalicylic acid
(Asp irin)
+
O
CH3 C- OH
Acetic acid
Phosphoric Anhydrides
The functional group of a phosphoric anhydride is
two phosphoryl (P=O) groups bonded to the same
oxygen atom.
O O
HO-P-O-P-OH
OH OH
D iphosph oric acid
(Pyroph os phoric acid)
O O
O-P-O-P-OO- OD iphosph ate ion
(Pyroph os phate ion)
O O O
HO-P-O-P-O-P-OH
OH OH OH
Triphosp horic acid
O O O
O-P-O-P-O-P-OO- O- OTriph os phate ion
ATP
Adenosine Triphosphate
Polyamides
Nylon-66 was the first purely synthetic fiber.
– It is synthesized from two six-carbon monomers.
remove H 2O
H
N
O
H
N
H
OH +
O
H
Hexanedioic acid
1,6-Hexanediamine
(Adipic acid)
(Hexamethyle nediami ne)
HO
heat
- H2 O
O
O
N
H
Nylon-66
(a polyamide)
H
N
n
Polyamides
The polyaromatic amide known as Kevlar is
made from an aromatic dicarboxylic acid and
an aromatic diamine.
remove H 2O
O
nHOC
O
COH
H
H
heat
+
N
N
-H2 O
H
H
1,4-Benzen edicarboxylic 1,4-Benzen ediamine
acid
(p-Phen ylened iamin e)
(Terep hthalic acid)
O
C
O
CNH
NH
Kevlar
(a p olyaromatic amide)
n
Polyesters
The first polyester involved polymerization of
this diester and diol.
remove CH 3 OH
O
OCH3
HO
+
CH3 O
O
Dimethyl terephthalate
OH
1,2-Ethaned iol
(Ethylene glycol)
O
heat
-CH3 OH
O
O
O
n
Poly(eth ylene tereph thalate)
(D acron , Mylar)
Polycarbonates
Lexan, the most familiar polycarbonate, is formed
by reaction between the disodium salt of bisphenol
A and phosgene.
remove N a+ ClO
CH3
+
Na-O
O- Na+ + Cl
CH3
D isodium salt of Bis phenol A
Cl
-NaCl
Phosgen e
O
CH3
O
CH3
Lexan
(a p olycarbonate)
O
n