4. Esterification and dehydration of alcohols

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Esterification
and
dehydration
of alcohols
Keywords:
Esterification,
elimination, ester,
dehydration
Starter:
Use molecular models to
make various alcohol
molecules
Learning Objectives
A
B
C
 Model the esterification of
alcohols with carboxylic acids
 Describe the elimination of H2O
from alcohols to form alkenes.
 Name the esters formed by
esterification reactions
Esterification – the reaction of an alcohol
with a carboxylic acid to produce an ester
and water
Elimination – breaking up 1 molecule into 2
molecules
Dehydration – an elimination reaction in
which water is removed from a saturated
molecule to make an unsaturated molecule
Esterification
An ester is formed when an alcohol is
warmed with a carboxylic acid in the
presence of an acid catalyst
The reaction is known as esterification
Concentrated sulfuric acid is often used as
the acid catalyst
The esterification reaction between
Propanoic acid and Methanol
In the reaction, the O-H bond in the alcohol
is broken and water is formed. The water
molecule comes from the OH of the
carboxylic acid group and the H in the
alcohol group
Naming esters
X-yl X-anoate
Alcohol
Carboxylic acid
Choose an alcohol and a carboxylic acid card.
Name the ester and draw its structure.
Esters are used as adhesives and solvents in
the chemical industry. The flavours and
fragrances of different esters are widely
used to produce food flavourings and
perfumes.
Preparing an ester
1. In a boiling tube add
1cm3 carboxylic acid to
1cm3 alcohol and add
the catalyst (H2SO4)
2. Place tube in a water
bath (80C) for 5 mins
3. Pour the product into a
beaker of cold water
4. The oil on the surface
will be the ester
Dehydration of an alcohol
An alcohol can be dehydrated to form an
alkene in the presence of an acid catalyst
(Conc phosphoric acid or conc sulphuric acid)
This is an elimination reaction
Alcohol is heated under reflux with the
catalyst for 40 minutes.
The dehydration of cyclohexanol is seen
below. What is the product?
Plenary
Pg 155
Questions 1, 2 and 3
Methanol
Methanoic acid
Ethanol
Ethanoic acid
Propanol
Propanoic acid
Butanol
Butanoic acid
Pentanol
Pentanoic acid
Hexanol
Hexanoic acid
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