Carboxylic Acids and Esters,
Carboxylic Acids
Properties of Carboxylic Acids
Esters
Esterification and Hydrolysis
1
Carboxyl Group
Carboxylic acids contain the carboxyl
group on carbon 1. It will be the first
carbon of the parent chain.
O

CH3 — C—OH =
CH3—COOH
carboxyl group
2
Naming Carboxylic Acids
Formula
IUPAC
alkan -oic acid
Common
prefix – ic acid
HCOOH
methanoic acid
formic acid
CH3COOH
ethanoic acid
acetic acid
CH3CH2COOH
propanoic acid
propionic acid
CH3CH2CH2COOH butanoic acid
butyric acid
3
Naming Rules
• Identify longest chain
• (IUPAC) Number carboxyl carbon as 1
• Name side chains alphabetically
CH3
|
CH3 — CH—CH2 —COOH
IUPAC
3-methylbutanoic acid
4
Naming Practice
Give IUPAC and common names:
A.
CH3COOH
CH3
|
B.
CH3CHCOOH
5
Solution
A.
CH3COOH
ethanoic acid; acetic acid
CH3
|
B.
CH3CHCOOH
2-methylpropanoic acid
6
Draw the Structures
• 3-methyl-4-phenylhexanoic acid
• pentanedioic acid
7
Properties
• Carboxylic acids are weak acids. They can be found in citrus
fruits and others with a sour taste. Vitamin C and ASA are other
common carboxylic acids.
CH3COOH + H2O
• Neutralized by a base
CH3COOH + NaOH
CH3COO– + H3O+
CH3COO– Na+ + H2O
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Properties
• The carboxyl groups consists of a polar hydroxyl group
bonded to the carbon of a carbonyl group. The presence of the
polar carbonyl and polar hydroxyl groups makes carboxylic
acids able to hydrogen bond with themselves and water.
• The smallest members (carbons 1-4) are soluble in water. As
the alkyl group (CH) becomes longer, the polarity of the
molecule decreases as does the solubility in water.
• Melting point increases with the size of the molecule. Analogous
acids with multiple carboxyl groups have higher melting points.
9
Learning Check
• Compare the melting point and solubility
in water of:
1-butanol
• butanal
• butane
• butanoic acid
10
Solution
• Lowest to highest melting point and
solubility:
• Butane (nonpolar, LDF only)
• Butanal (polar, LDF, DDF, no hydrogen bonding with self )
• 1-Butanol (polar, LDF, DDF, hydrogen bonding with self
and water)
• Butanoic Acid (most polar functional group, LDF, DDF,
hydrogen bonding with self and water)
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Reactions of Carboxylic Acids
• Oxidation of a Primary Alcohol to Aldehyde
• Further Oxidation to a Carboxylic Acid
•
*Ketones are not oxidized further
12
Esters
In and ester, the H in the carboxyl group is
replaced with an alkyl group (COO)
O

CH3 — C—O —CH3 = CH3—COO —CH3
ester group
13
Esters in Plants
Esters give flowers and fruits their
pleasant fragances and flavours.
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Naming Esters
• Name the alkyl from the alcohol –O• Name the acid with the C=O with –ate (drop “ic”
from acid name and and “ate)
acid
alcohol
O

methyl
CH3 — C—O —CH3
Ethanoate
(acetate)
methyl ethanoate (IUPAC)
methyl acetate (common)
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Some Esters and Their Names
Flavor/Odour
Raspberries
HCOOCH2CH3
ethyl methanoate (IUPAC)
ethyl formate (common)
Pineapples
CH3CH2CH2 COOCH2CH3
ethyl butanoate (IUPAC)
ethyl butyrate (common)
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Practice
Give the IUPAC and common names of
the following compound, which is
responsible for the flavor and odour of
pears.
O

CH3 — C—O —CH2CH2CH3
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Solution
O
ethanoic acid

propyl (propanol)
CH3 — C—O —CH2CH2CH3
propyl ethanoate (IUPAC)
propyl acetate (common)
18
Practice
Draw the structure of the following compounds
and name the alcohol and acid used to
synthesize the ester:
A. 3-bromobutanoic acid
B. Ethyl propanoate
19
Solution CA 3
A. 3-bromobutanoic acid
Br
|
CH3CHCH2COOH
B. Ethyl propanoate (ethanol and propanoic acid)
O

CH3 CH2 COCH2CH3 CH3CH2COOCH2CH3
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Esterification
• Reaction of a carboxylic acid and alcohol
• Acid catalyst and heat
O

H+
CH3 — C—OH + HO—CH2CH3
O

CH3 — C—O—CH2CH3 + H2O
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Ester Practice
• Illustrate the reaction between the acids
and alcohols listed and name the ester
• (i) 3-methylbutanoic acid and methanol
• (ii) benzoic acid and ethanol
22
Solution
• (i)
• (ii)
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Hydrolysis
• Esters react with water and acid catalyst
• Split into carboxylic acid and alcohol
O

H+
H — C—O—CH2CH3 + H2O
O

H — C—OH
+ HO—CH2CH3
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Saponification
• Esters react with a bases
• Produce the salt of the carboxylic acid and
alcohol
O

CH3C—OCH2CH3 + NaOH
O

CH3C—O– Na+
+
HOCH2CH3
salt of carboxylic acid
25
More Practice
Write the equation for the reaction of
pentanol and 3-chlorobutanoic acid in the
presence of an acid catalyst.
26
Solution
27
Reaction Practice
What are the organic products when
methylacetate (ethanoate) reacts with
A. Water and an acid catalyst?
B. KOH?
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Solution
A.
O

CH3COH
+
HOCH3
O

B.
CH3CO– K+
+ HOCH3
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POLYESTERS
• Esters can form long chain polymers
called polyesters.
• Examples
30
Properties of Esters
• The loss of the polar OH group in the
esterification rxn results in esters being less
polar, less soluble in water than their parent
carboxylic acids and alcohols.
Lower mass esters are detected by scents
because they are gases at room temperature.
Larger, heavier esters tend to be waxy solids.
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