Transcript Carboxylic Acids and Esters

1 of 31
© Boardworks Ltd 2009
2 of 31
© Boardworks Ltd 2009
Where are carboxylic acids found?
3 of 31
© Boardworks Ltd 2009
What are carboxylic acids?
Carboxylic acids contain a functional group of carbon,
hydrogen and oxygen atoms arranged like this...
...which is written as –COOH.
E.g.
methanoic acid (HCOOH)
ethanoic acid (CH3COOH)
What do you think the carboxylic acid with three carbon atoms
is called?
4 of 31
© Boardworks Ltd 2009
Naming carboxylic acids
5 of 31
© Boardworks Ltd 2009
Making carboxylic acids
If you leave wine standing open to the air, oxygen from the air
will oxidize the ethanol to ethanoic acid, forming vinegar.

+
ethanol
oxygen
+
ethanoic acid
water
In fact, any carboxylic acid can be made by oxidizing the
corresponding alcohol.
Q) Which carboxylic acid is made when methanol is oxidized?
A) Methanoic acid.
6 of 31
© Boardworks Ltd 2009
Properties of carboxylic acids
Carboxylic acids:
 have relatively high melting and boiling points
 are very soluble in water
 are weak acids
 have a characteristic smell!
Examples of everyday carboxylic acids include:
 citric acid (found in citrus fruits)
 lactic acid (found in tired muscles)
 malic acid (found in sour and tart foods).
7 of 31
© Boardworks Ltd 2009
Match the properties
8 of 31
© Boardworks Ltd 2009
Chemical properties of carboxylic acids
Carboxylic acids are typical weak acids.
What would happen if you added a few cm3 of dilute ethanoic
acid to each of these substances?
 A few drops of universal
indicator.
 3 cm3 sodium hydroxide
solution.
 Half a spatula of sodium
carbonate.
 A piece of magnesium
ribbon.
9 of 31
© Boardworks Ltd 2009
Reactions of carboxylic acids
10 of 31
© Boardworks Ltd 2009
Reactions of carboxylic acids
Carboxylic acids react like any other type of acid, forming
salts when they react with alkalis, carbonates and metals:
ethanoic acid +
CH3COOH
ethanoic acid +
2CH3COOH
+
+
11 of 31
NaOH
sodium

carbonate
Na2CO3
ethanoic acid +
2CH3COOH
sodium

hydroxide
+
+
water
CH3COONa
+
H 2O
sodium
ethanoate
+
carbon
+ water
dioxide
 2CH3COONa +
sodium
2Na

sodium
ethanoate

sodium
ethanoate
CO2
+
H 2O
+ hydrogen
 2CH3COONa +
H2
© Boardworks Ltd 2009
Reactions of carboxylic acids
12 of 31
© Boardworks Ltd 2009
Reactions of carboxylic acids
13 of 31
© Boardworks Ltd 2009
14 of 31
© Boardworks Ltd 2009
Carboxylic acids in descalers
In hard water areas, limescale (calcium carbonate) builds up
in kettles and water pipes.
To remove the limescale, a
descaler can be used, which
contains ethanoic acid.
What reaction takes place
between the ethanoic acid
and limescale?
ethanoic acid +
2CH3COOH
15 of 31
+
calcium

carbonate
CaCO3
calcium
ethanoate
+
 (CH3COO)2Ca +
carbon
+ water
dioxide
CO2
+
H 2O
© Boardworks Ltd 2009
Carboxylic acids in soaps
Fatty acids are carboxylic acids with very long carbon chains.
The sodium and potassium salts of fatty acids can be used
as soaps.
For example, reacting octadecanoic acid with sodium
hydroxide produces sodium octadecanoate, a common soap.
+
(octadecanoic acid)
+
(sodium octadecanoate)
16 of 31
© Boardworks Ltd 2009
Carboxylic acids: summary
17 of 31
© Boardworks Ltd 2009
18 of 31
© Boardworks Ltd 2009
What are esters?
Esters have characteristic smells, and are
often used in flavourings and perfumes.
For example:
 propyl ethanoate smells of pears
 butyl butanoate smells of pineapple
 methyl butanoate smells of apple.
19 of 31
© Boardworks Ltd 2009
Esters
Esters contain this group of atoms:
...which is written as –COO–.
Esters are made from the reaction of a carboxylic acid with an
alcohol:
carboxylic acid + alcohol  ester + water
propanoic acid + methanol  methyl propanoate + water
CH3CH2COOH +
+
20 of 31
CH3OH


CH3CH2COOCH3
+ H2O
+
© Boardworks Ltd 2009
Naming esters
Esters are named after the alcohol and the carboxylic acid
from which they are made. The alcohol gives the first part
of the name, and the carboxylic acid gives the second.
Esters always end in “–anoate”.
For example:
ethanoic acid
methanol
methyl ethanoate
21 of 31
© Boardworks Ltd 2009
Matching carboxylic acids to their esters
22 of 31
© Boardworks Ltd 2009
Practising naming esters
23 of 31
© Boardworks Ltd 2009
24 of 31
© Boardworks Ltd 2009
How are esters made?
Esters are made by reacting a
carboxylic acid with an alcohol.
However, the reaction is very
slow at room temperature.
How could you speed it up?
 The reactants could be
heated in order to make the
reaction faster.
 A catalyst of concentrated
sulfuric acid could be added.
25 of 31
© Boardworks Ltd 2009
Making esters
26 of 31
© Boardworks Ltd 2009
What are the stages in making an ester?
27 of 31
© Boardworks Ltd 2009
28 of 31
© Boardworks Ltd 2009
Glossary
29 of 31
© Boardworks Ltd 2009
Anagrams
30 of 31
© Boardworks Ltd 2009
Multiple-choice quiz
31 of 31
© Boardworks Ltd 2009