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+
CH3—C—OH + H—O—CH2—CH3
O
||
CH3—C—O—CH2—CH3 + H2O
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:
1180
C 780
C 540
C 1000
C
Q1 What does reversible mean?
∆H 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
||
CH3 —C—O—CH3
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
||
CH3—O—C —CH3
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
2cm3
of Pentan-1-ol,
2cm3
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.
CH3C
CH2 O
O
CH3
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.
ethyl ethanoate
CH3CCH2 O
O
CH3
Either…
Or…
CH3C CH2O
O
CH3
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 (H2SO4)
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
H2O
+
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

24. CH3
CH
CH2 O
O
CH3
CH2C
CH3 O
O
CH
CH3 O
O
ethyl methanoate
methyl propanoate
methyl methanoate

25. R
R’C
H2O
+
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.

26. +
OH
OH- →
CH3C
CH2 O
O
CH3
ethyl ethanoate
+
CH2CH3
CH3C
-
O
O
ethanol
ethanoate ionnot a reaction that exists
in equilibrium (unlike
using acid catalyst)