Announcements & Agenda (03/30/07)
Quiz on Wednesday (Chirality & Ch 13)
Will hand out HW practice on Monday
Schedule for rest of semester on M or W
<10 people at review on Wed 

Great place for help!
Today
 Fisher projections (12.6)
 Carboxylic acids (13.1, 13.2)
 Esters (13.3)
1
Fischer Projections of Chiral Molecules
(12.6)
• are a 2-dimensional representation of a 3-D
molecule.
• places the most oxidized group at the top.
• uses vertical lines in place of dashes for
bonds that go back.
• uses horizontal lines in place of wedges for
bonds that come forward.
2
Drawing Fischer Projections
3
D and L Notations
• By convention, the letter L is assigned to the
structure with the —OH on the left.
• The letter D is assigned to the structure with the
—OH on the right.
• FYI: Other conventions exist too…
4
Learning Check
Indicate whether each pair is a mirror image
that cannot be superimposed (enantiomers).
CH2OH
A.
B.
H
H
C
CH3
CH2OH
and
CH3 C
Br
Br
Cl
Cl
C
H
CH3
and
CH3 C
H
Yes
H
No
H
5
Carboxylic Acids (13.1)
6
Ch 13 Practice Problems
13.01, 13.07, 13.09, 13.11, 13.13,
13.15, 13.17, 13.19, 13.21, 13.25,
13.29, 13.31, 13.33, 13.37, 13.39,
13.41, 13.43, 13.49, 13.55, 13.57,
13.59, 13.63, 13.65, 13.67, 13.69,
13.71, 13.73, 13.74, 13.75, 13.76
7
Carboxylic Acids
A carboxylic acid contains a carboxyl group, which
• is a carbonyl group (C=O) attached to a hydroxyl
group (—OH).
O

CH3 — C—OH
hydroxyl group
carbonyl group
Will also see a carboxylic acid written as CH3COOH
8
Recognizing Carboxylic Acids from Names
The IUPAC names of carboxylic acids:
• Replace the -e in the alkane name with -oic acid.
CH4
methane HCOOH
CH3—CH3 ethane
methanoic acid
CH3—COOH ethanoic acid
• Number substituents from the carboxyl carbon 1.
CH3
O
|
║
Don’t need to
CH3—CH—CH2—C—OH
know numbering
4
3
2
1
rules!!!
3-methylbutanoic acid
9
Names & Sources of Some Carboxylic Acids
(Know These)
By the way, very common in nature:
Citric acid, tartaric acid, lactic acid, fatty acids, etc.
10
Polarity of Carboxylic Acids
• strongly polar because they have two polar groups:
[hydroxyl (−OH) and carbonyl (C=O)]
• form dimers in which hydrogen bonds form
between two carboxyl groups.
O … H—O
||
|
CH3—C
C—CH3
|
||
O—H … O
A dimer of acetic acid
• have higher boiling points than alcohols, ketones,
and aldehydes of similar mass.
11
Comparison of Boiling Points
Compound
O
║
CH3−CH2−C−H
Molar Mass
Boiling Point
58
49°C
CH3−CH2−CH2−OH
60
97°C
O
║
CH3−C−OH
60
118°C
12
Solubility in Water
Carboxylic acids:
• form hydrogen
bonds with many
water molecules.
Water molecules
• with 1-4 carbon
atoms are very
soluble in water.
13
Boiling Points and Solubility
14
Acidity of Carboxylic Acids
Carboxylic acids
• are weak acids.
• ionize in water to produce carboxylate
ions and hydronium ions.
O
║
CH3−C−OH + H2O
O
║
CH3−C−O– + H3O+
~1%
15
Neutralization of Carboxylic Acids
Carboxylic acid salts
• are a product of the neutralization of a carboxylic acid
with a strong base.
CH3—COOH + NaOH
CH3—COO– Na+ + H2O
acetic acid
sodium acetate
(carboxylic acid salt)
• are used as preservatives and flavor enhancers.
16
Learning Check
Write the equation for the reaction of propanoic acid with
A. water
CH3—CH2—COOH + H2O
CH3—CH2—COO– + H3O+
B. KOH
CH3—CH2—COOH + KOH
CH3—CH2—COO– K+ + H2O
17
Esters (13.3)
18
Esters
In an ester, the H in the carboxyl group is replaced
with an alkyl group.
O

CH3 — C—O —CH3
ester group
19
Esterification
Esterification: reaction of a carboxylic acid &
alcohol in the presence of an acid catalyst to
produce an ester.
O

CH3—C—OH + H—O—CH2—CH3
H+
O
Also called a condensation reaction!

CH3—C—O—CH2—CH3 + H2O
ethyl acetate (an ester)
FYI: The acid half of an ester is called an “acyl” group
20
Learning Check
Write the equation for the reaction of propanoic
acid and methanol in the presence of an acid
catalyst.
O

H+
CH3—CH2—C—OH + H—O—CH3
propanoic acid
methanol
O

CH3—CH2—C—O—CH3 + H2O
21
Ester Products
Aspirin
• is used to relieve pain
and reduce inflammation.
• is an ester of salicylic
acid and acetic acid.
Oil of wintergreen
• is used to soothe sore
muscles.
• is an ester of salicylic
acid and methanol.
O
C OH
O
O C CH3
O
C O CH3
OH
22
Naming Esters
The name of an ester contains the names of
• the alkyl group from the alcohol.
• the carbon chain from the acid with –ate ending.
methyl
ethanoate (acetate)
O

-oate: means
CH3— O—C —CH3
ester present
IUPAC: methyl ethanoate
common: methyl acetate
23
Esters in Plants
Esters give flowers and fruits their
pleasant fragrances and flavors.
24
Acid Hydrolysis of Esters
• an ester reacts with water to produce a
carboxylic acid and an alcohol.
• an acid catalyst is required.
O

H+
H—C—O—CH2—CH3 + H2O
O

H—C—OH
+ H—O—CH2—CH3
25
Base Hydrolysis (Saponification)
• is the reaction of an ester with a strong base.
• produces the salt of the carboxylic acid and an
alcohol.
O
||
CH3—C—O—CH2—CH3 + NaOH
O

CH3—C—O– Na+ + HO—CH2—CH3
salt of carboxylic acid
alcohol
26
Base Hydrolysis of Fatty Acids
Produces Soaps
27
Carboxylic acids with lots of carbons are fatty
acids (usually even #, 10, 12, 14, 16, 18)
Sodium salts of fatty
acids are soaps.
28
Cleaning Action of Soap
A soap
• contains a nonpolar
end that dissolves in
nonpolar fats and oils,
and a polar end that
dissolves in water.
• forms groups of soap
molecules called
micelles that dissolve in
water and are washed
away.
29
Learning Check
Write the organic products when methyl acetate
reacts with
A. water and an acid catalyst.
O

CH3—C—OH + HO—CH3
B. KOH.
O

CH3—C—O– K+
+ HO—CH3
30