Transcript Chemistry 2100

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
O
RC O H
A carboxylic acid
O
O
RC O C R'
RC O R'
RC N H 2
A n ester
An anhydride
O
RC - O H H - O CR '
A n amide
- H2 O
- H2 O
O
O
O
RC - O H H - O R'
- H2 O
O
RC - O H H - N H 2
O
C
R
[
Y
acyl
acetyl = Ac: R = CH3 ]
Y =
O
OH
Cl
CO R'
OR'
NR 2
carboxylic acid
acid chloride
anhydride
ester
amide
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
O
CH3 COCH2 CH3
Ethyl ethanoate
(Ethyl acetate)
O
O
Diethyl pentanedioate
(Di ethyl glutarate)
O
O
O
A f ive-membered
lactone
O
O
C
R
+
Y
H
C
Z
R
+
Z
H
Y
O
C
R
O


Y
+

H

C
Z
R
+
Z
H
Y
O
C
R
O


Y
+

H

C
Z
R
+
Z
H
Y
O
C
R
O


Y
+

H

C
Z
R
+
Z
H
Y
O
C
R
O


Y
+

H

C
Z
R
+
Z
OR'
H
Y
O
C
R
O


Y
+

H

Z
OR'
C
R
+
Z
OR'
H
Y
O
C
R
O


Y
OH
+

H

Z
OR'
C
R
+
Z
OR'
H
Y
O
C
R
O


Y
OH
+

H

Z
OR'
C
R
+
Z
OR'
H
OH
Y
Fischer esterification
O

C
R
O

Y
OH
+

H

Z
OR'
H
+
C
R
+
Z
OR'
H
OH
Y
Hydrolysis of Esters
O
CH 3 CO CH 2 CH 3
Eth yl ace tate
H
+
H2 O
+
O
CH 3 CO H
A ce ti c ac i d
+
CH 3 CH 2 O H
Eth an o l
Saponification
O
C H 3 C O C H 2 C H 3+ N a O H
Ethyl acetate
Sodium
hydroxide
H2 O
heat
O
C H 3 C O - N a ++ C H 3 C H 2 O H
Sodium
acetate
Ethanol
Properties of Esters
ethyl butyrate
pineapple
octyl acetate
orange
O
C
OH
coumarin
clover
methyl salicylate
methyl anthranilate
OCH
3
NH
NH22
wintergreen
grape
methyl anthranilate
grape
Triglycerides & Waxess
O
CH
O
C
(oleic)
O
2
O
CH
CH
C
O
2
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
Ethyl 2-phenyl acetate
+ NH
3
N H2
2-Phenylacetami de
+
CH3 CH2 OH
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
O
O
CH 3 CNH 2
CH 3 CNH CH 3
HCN ( CH 3 ) 2
A ce tam i d e
(a 1° am i d e )
N -M e th y l ace tam i d e
(a 2° am i d e )
N ,N - D im e th y l f orm am i d e
(a 3° am i d e )
•
• •
O
•
•
•
R'
••
O
•
•
R'
••
R
C
R
N
R"
C
N
R"
•
• •
O
•
•
•
R'
••
O
•
•
R'
••
R
C
R
N
R"
C
N
R"
•
• •
O
•
•
•
R'
••
O
•
•
R'
••
R
C
R
N
R"
C
N
R"
•
• •
O
•
•
•
R'
••
O
•
•
R'
••
R
C
R
N
R"
C
N
R"
•
• •
O
•
•
•
R'
••
O
•
•
R'
••
R
C
R
N
R"
C
N
R"
Amides
A cyclic amide is called a lactam.

b
O
O
NH
NH
A fo u r-m e m b e re d l ac tam
(a b -l actam )
A s e v e n -m e m b e re d l ac ta m
– The penicillins are referred to as b-lactam
antibiotics.
HO
T h e p e n i ci l l i n s
d i f f e r i n th e gro u p
b o n d e d to th e
carb o n y l carb o n
T h e b -l actam ri n g
O
N H2
N
H
O
A m o xi ci l l i n
S
N
CH 3
CH 3
COO H
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
O
CH 3 C-O H + H 2 NCH 2 CH 3
A c e ti c
aci d
Eth an am i n e
(Eth y l am i n e )
-
+
CH 3 C-O H 3 NCH 2 CH 3
A n am m o n i u m
s al t
O
h e at
CH 3 C-N HCH 2 CH 3 + H 2 O
A n am i d e
Preparation of Amides
• It is much more common, however, to
prepare amides by treating an
anhydride with an amine.
O
O
CH 3 C- O-CCH 3 + H 2 N CH 2 CH 3
A ce ti c an h d y ri d e
O
O
CH 3 C-N HCH 2 CH 3 + CH 3 COH
A n am id e
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
CH 3 C- O -CCH 3
A ce ti c a n h y d rid e
Reaction with Alcohols
Anhydrides react with alcohols and phenols to
give an ester and a carboxylic acid.
O O
O
CH3 COCCH3 + HOCH2 CH3
Acetic anhydride
O
C H 3 C O CH 2 CH 3 + H O C C H 3
Ethyl acetate
Ethanol
Acetic acid
Aspirin is prepared by the reaction of salicylic
acid with acetic anhydride.
C O OH
O
OH
Sali cylic acid
+
O
CH3 C- O -CCH3
Acetic anh ydride
C O OH
O C CH 3
O
Acetylsalicylic aci d
(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
O
-
H O- P- O- P- OH
O -P- O -P- O
OH O H
D i p h o s p h o ri c ac id
(Py rop h os p h o ri c aci d )
O
O
O
OH OH OH
T ri p h o s p h o ri c ac i d
-
O
-
-
D i p h o s p h ate i on
(Py rop h os p h ate i o n )
O
HO -P -O -P -O -P -O H
O
O
-
O
O
O - P-O - P-O - P-O
O
-
O
-
O
-
-
T ri p h os p h ate i o n
ATP
Adenosine Triphosphate
Polyamides
Nylon-66 was the first purely synthetic fiber.
– It is synthesized from two six-carbon monomers.
remove H
2O
H
O
HO
O
Hexanedi oic acid
(Adi pic acid)
H
N
OH +
H
N
H
heat
- H2 O
1,6-Hexane diamine
(Hexamethylene diamine)
H
O
N
O
H
Nylon-66
(a pol yamide)
N
n
Polyamides
The polyaromatic amide known as Kevlar is
made from an aromatic dicarboxylic acid and
an aromatic diamine.
re m o v e H 2 O
O
nHO C
O
CO H
H
H
N
+
h e at
N
H
-H 2 O
H
1,4-B e n z e n e d i carb o xyl i c 1,4-B e n z e n e d i am i n e
aci d
(p - Ph e n yl e n e d i am i n e )
(T e re p h th al i c ac i d )
O
O
C
CN H
NH
n
K e v l ar
(a p ol y arom ati c am i d e )
Polyesters
The first polyester involved polymerization of
this diester and diol.
re m o v e CH 3 O H
O
OCH 3
HO
h e at
+
CH 3 O
O
D i m e th y l te re p h th al ate
OH
-CH 3 O H
1,2-E th an e d i ol
(E th y l e n e g l yco l )
O
O
O
O
n
Po l y(e th yl e n e te re p h th al ate )
(D acron , M yl ar)
Polycarbonates
Lexan, the most familiar polycarbonate, is formed
by reaction between the disodium salt of bisphenol
A and phosgene.
+
re m o v e N a C l
-
O
CH 3
+
-
Na O
-
O Na
+
CH 3
D i s o d i u m s al t o f B i s p h e n o l A
+ Cl
Cl
- Na Cl
P h o s ge n e
O
CH 3
O
CH 3
Le xan
(a p ol y carb o n ate )
O
n