Esterification

Allahyar ( Shahzaib ) Shar
QUEST Nawabshah
Chemical Engineering

1. QUEST Nawabshah

2. 2
Esterification is The reaction of a carboxylic acid
(Ethanoic acid)and alcohol in the presence of an
acid catalyst to produce an ester.
O
|| H
+
CH
3
—C—OH + H—O—CH
2
—CH
3
O
||
CH
3
—C—O—CH
2
—CH
3
+

H
2
O
ethyl acetate (an ester)

3. Esterification is the general name for a chemical reaction in which
two reactants (typically an alcohol and an acid) form an ester as
the reaction product.
For example:
Acetic acid in excess ethanol (possibly as the solvent) in the
presence of concentrated sulfuric acid as a catalyst results in an
ester (ethyl acetate).

4. The esterification reaction is both slow and reversible.
The equation for the reaction between ethanoic acid
and ethanol is:
118
0
C 78
0
C 54
0
C 100
0
C

Q1 What does reversible mean?
DH of the forward reaction is -20kJ.mol-1
Q2 How can we favour the forward reaction and make more Ester?
Q3 Why do we warm the reaction mixture?

5. 5
In an ester,
•The H in the carboxyl group is
replaced
with an alkyl group.
O
||
CH
3
—

C—O—CH
3

ester group

6. 6
The name of an ester contains the names of
•The alkyl group from the alcohol.
•The carbon chain from the acid with –ate ending.
O
||
CH
3
—

O—C —CH
3
ethanoate (acetate)
IUPAC: methyl ethanoate
common: methyl acetate

10. Diagram to show the bonds broken during
esterification

12. Simple laboratory preparation of an ester
Making Pentyl Ethanoate
2cm
3
of Pentan-1-ol,
2cm
3
of glacial
ethanoic acid. Add a
few drops of
concentrated
sulfuric acid.
HAZARDOUS

13. •Pembrokeshire has a vineyard which produces wines with fine
flavours produced by esters.
•Research has identified 11 different esters in grape juice, but
wine can have up to 83; this affects the wine’s flavour and
complexity in proportion
to their presence. Esters are formed when an acid reacts with
alcohol, eliminating a water molecule in the process.
Ethyl esters have a strong influence on a wine’s aroma here are
three examples;
•ethyl hexanoate, fruity, strawberry, green apple and anise
•ethyl octanoate, with sweet, fruity, ripe fruit, burned and beer
characteristics
•ethyl decanoate, which imparts an oily, fruity and floral
character.

14. Sweet-smelling esters
Explain how you would make Octyl Ethanoate

15. •Esterification is a reversible reaction
•The reversed reaction is called Hydrolysis.
•As a result of this reversibility, many
Esterification reactions are equilibrium
reactions.
•Esterifications are among the simplest and
most often performed organic
transformations.

16. 16
Esters in Plants
Esters give
flowers and
fruits their
pleasant
fragrances
and flavors.
TABLE 16.4
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

17. 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

18. 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!

19. Structural formulae
Although the previous structural formula are the clearest
way of showing esters, they can draw out in a
shortened form.
ethylethanoate
CH
3
CCH
2
O
O
CH
3
Either…
Or…
CH
3
C CH
2O
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.

20. 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

21. 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.

22. 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.

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

24. 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

25. R
R’C
H
2
O
+
OH
HO
O
R’C
RO
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.

26. +
OH
OH
-→
CH
3
C
CH
2
O
O
CH
3
ethylethanoate
+
CH
2
CH
3
CH
3
C
-
O
O
ethanol
ethanoate ionnot a reaction that exists
in equilibrium (unlike
using acid catalyst)