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More to Know! Sugarcane plants are one of the most efficient convertors of sunlight into chemical
as a fuel
Alcohol
fuel
a
Alcohol as a fuelas a fuel
Alcohol as
Alcohol
Alcohol as a fuel
energy. Sugarcane juice can be used to prepare molasses which is fermented to give
alcohol (ethanol). Some countries now use alcohol as an additive in petrol since it is a
cleaner fuel which gives rise to only carbon dioxide and water on burning in sufficient
air (oxygen).
4.4.2 Properties of Ethanoic Acid

Ethanoic acid is commonly called acetic acid and
Activity
Activity 4.74.7
Activity 4.7
Activity 4.7
belongs to a group of acids called carboxylic Activity 4.7
acids. 5-8% solution of acetic acid in water is
n Compare the pH of dilute acetic acid
called vinegar and is used widely as a preservative
and dilute hydrochloric acid using
in pickles. The melting point of pure ethanoic acid
is 290 K and hence it often freezes during winter both litmus paper and universal
indicator.
in cold climates. This gave rise to its name glacial
n Are both acids indicated by the
acetic acid.
litmus test?
The group of organic compounds called n Does the universal indicator show
carboxylic acids are obviously characterised by them as equally strong acids?
their acidic nature. However, unlike mineral acids
like HCl, which are completely ionised, carboxylic
acids are weak acids.
Activity
Activity
Activity 4.8
4.8
Activity 4.8
Activity 4.84.8
n Take 1 mL ethanol (absolute alcohol)
and 1 mL glacial acetic acid along
with a few drops of concentrated
sulphuric acid in a test tube.
n Warm in a water-bath for at least five
minutes as shown in Fig. 4.11.
n Pour into a beaker containing
20-50 mL of water and smell the
resulting mixture.
acid:
Reactions
Reactions of ethanoic acid:
Reactions
Reactions of ethanoic acid:of ethanoic acid:
ethanoic
Reactions of of ethanoic acid:
(i) Esterification reaction: Esters are most commonly
formed by reaction of an acid and an alcohol.
Ethanoic acid reacts with absolute ethanol in the
presence of an acid catalyst to give an ester –
Figure
Figure 4.11
Figure
4.11
Figure 4.114.11
Figure 4.11
Acid Formation of ester
O
− −
CH − COOH CH − CH OH CH − C C CH − CH + H O
+
3 3 2 3 2 3 2
11
O
(Ethanoic acid) (Ethanol) (Ester)
t
Generally, esters are sweet-smelling substances. These are used in
making perfumes and as flavouring agents. On treating with sodium
hydroxide, which is an alkali, the ester is converted back to alcohol
and sodium salt of carboxylic acid. This reaction is known as
saponification because it is used in the preparation of soap. Soaps
are sodium or potassium salts of long chain carboxylic acid.
Carbon and its Compounds 73
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