Carboxylic acids, esters, amines, and amides

Esters
C.I. 13.5

What are they?
How are they made?

Formed when an alcohol reacts with a
carboxylic acid.

Very
slow
reaction, unless! an acid catalyst
used (usually sulphuric acid)

A condensation reaction

The condensation reaction between the
hydroxyl group and the carboxylic acid
known as
esterification
.

Reverse reaction =
ester hydrolysis

Naming
Named after alcohol & carboxylic acid from
which they are derived.
Names of esters
end in –oate.

CH
3
C
CH
2
O
O
CH
3
ethyl ethanoate
this part from the acid
and is named after it
this part comes from the
alcohol & is named after it
let’s name
some esters!

Structural formulae
Although the previous structural formula are the clearest
way of showing esters, they can draw out in a
shortened form.
ethyl ethanoate
CH
3
C
CH
2
O
O
CH

3
Either…
Or…
CH
3
C
CH
2
O
O
CH
3
In this version
the acid part
has been
written first

Identify the group attached to the C=O – this is from
the acid

The group attached to the –O- is from the alcohol.

Wait! What’s that smell?
•
Esters have strong, sweet smells.
•
Their bouquet is often floral or fruity.
•
This means they are used in food flavourings &
perfumes.

•
Also, very good at dissolving organic compounds so
often used as solvents.
ester fragrance
ethyl methanoate raspberries
3-methylbutyl ethanoate pears
ethyl 2-methylbutanoate apples
phenylmethyl ethanoate jasmine

Esters from phenols
•
-OH group in phenol less reactive
to esterification, requires a more
vigourous reagent.
•
Use of ethanoic acid in
esterification is also known as
ethanoylation.
•
Ethanoic anhydride is a more
vigourous ethanoylating agent
OH

Esters from phenols
•
Ethanoic anhydride used as it is reactive
but not too dangerous.
•
Ethanoyl chloride is much more reactive,
but, also toxic and hazardous to

use.
•
Ethanoic anhydride & ethanoyl chloride
are described as acylating agents

using an acylating agent is the only way to esterify a
phenol

alcohols can be esterified using acylating agents or by
reacting with a carboxylic acid.

Ester hydrolysis

Breakdown of an ester by water.

Process sped up by catalysis

Can use an acid to catalyse (H
2
SO
4
)

Alkali catalysts (e.g. sodium hydroxide) can
also be used but instead of producing
carboxylic acid a carboxylate salt is
formed.

Alkaline hydrolysis goes to completion &
hence is usually preferred.

This is why it is a
condensation reaction
because water is produced!
R
R’C
H
2
O
+
O H
H O
O
R’C
R O
O
+
⇋
Definition of a condensation reaction =
two molecules reacting to form a larger
molecule with the elimination of a
small molecule such as water

CH
3
CH
CH
2
O
O

CH
3
CH
2
C
CH
3
O
O
CH
CH
3
O
O
ethyl methanoate
methyl propanoate
methyl methanoate

R
R’C
H
2
O
+
O H
H O
O
R’C
R O
O

+
⇌
FORWARD REACTION = condensation reaction,
the esterification of an alcohol using
acid catalyst under reflux.
REVERSE REACTION = ester hydrolysis, same
catalyst works for both forward & reverse
reactions.

+
OH
OH
-
→
CH
3
C
CH
2
O
O
CH
3
ethyl ethanoate
+
CH
2
CH
3
CH

3
C
-
O
O
ethanol
ethanoate ion
not a reaction that exists
in equilibrium (unlike
using acid catalyst)