Carboxylic acids contain the carboxyl functional group.
The hydroxyl group –OH, and the carbonyl group, C=O, make the carboxylic acid more
polar than either an alcohol or a carbonyl.
Naming of carboxylic acids

Remove the final –e from the alkane and add the ending -oic acid
Examples
CH3CH2CH2CH2CH2CH2CH2COOH
Name:
octanoic acid
Name:
propanoic acid
O
C2H5
C
OH
Like the aldehydes, the carboxylic acid carbon is always number one in the chain although
again the number one is not included in the name.
H
H
4
C
3
H
Cl
H
C
2
C
H
H
CH3
O
1
C
Name:
3-chlorobutanoic acid
Name:
3-methylhexanoic acid
OH
O
OH
Student activity 1
1. Name each of the following molecules
O
C4H9
C
OH
………………………………………………………………………………
1
CH3
H3C
C
O
C
………………………………………………………………………………
OH
H
O
C2H5
C
………………………………………………………………………………
OH
O
OH
………………………………………………………………………………
O
OH
………………………………………………………………………………
2. Draw each of the following structures, using full displayed formula
2-methylnonanoic acid
methanoic acid
butan-1,4-dioic acid
3-methylbutanoic acid
Reactions of Carboxylic acids
Carboxylic acids are like any other acid, only they are weak in comparison to acids such as
They will carry out the typical reactions of acids, reacting with metals, bases and
carbonates.
How is the term acid defined?
………………………………………………………………………………
Why are carboxylic acids defined as weak acids?
……………………………………………………………………………………………….
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Reactions of carboxylic acids
Write fully balanced equations for the reaction between a carboxylic acid (ethanoic acid)
and a:(a) Base (Sodium Hydroxide)
……………………………………………………………………………………………….
The product formed in the reaction above is a salt because an acid reacts with a base to
produce salt and water. In the above reaction we call the salt a carboxylate. Because the
acid is ethanoic acid, the product is an ethanoate.
(b) Metal (Sodium)
……………………………………………………………………………………………….
(c) Carbonate (Sodium carbonate)
……………………………………………………………………………………………….
Note that although carboxylic acids do react with carbonates and Mg at room temperature-phenols don’t
The carboxylate ion
The carboxylate ion is formed whenever a carboxylic acid is added to an alkali:
Ionic Bonding
H
H
O
O
H
C
C
+
OH-
H
OH
H
C
H2O
O-
H
Carboxylic acids exist
in acid conditions.
+
C
Carboxylates exist
in alkali conditions.
d) Esterification
i) The reaction between an alcohol and a carboxylic acid.
The reaction requires the use of a sulphuric acid catalyst. The reaction is reversible and
reaches equilibrium.
Write the equation for the reaction between ethanoic acid and methanol.
………………………………………………………………………………………………………….
It is sometimes easier to draw out the structures in order to work out the product. If you
draw them this way you should always get the answer correct.
H
H
C
H
O
+
C
H
H
O
H
O
H
ethanoic acid
C
CH3
H
methanol
3
O
C
+
O
H2O
CH3
methylethanoate
water
i) The reaction between an alcohol and an acid anhydride. Below is ethanoic anhydride
(acetic anhydride).
Write the equation for the reaction between ethanoic anhydride and methanol. It produces
an ethanoic acid molecule as well as the ester.
………………………………………………………………………………………………………….
………………………………………………………………………………………………………….
Student activity 2
1. What are the forces in between the molecules (vdw, pd or H-bonding)? Would you expect
the acid to be soluble in water?
2. Draw a diagram to show the interaction between ethanoic acid and water.
There are a number of other organic materials which can be made directly from a carboxylic
acid, some of which have been discussed above. These include: Carboxylate salts
 Esters
 Acyl chlorides
 Amides
 Acid Anydrides
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Carboxylates are ionic compounds that are bonded together by strong electrostatic forces
of attraction.
Properties: 
O
C4H9

C

O-Na+
Esters contain the following functional group:
They are made when a carboxylic acid, in the presence of an acid catalyst, or an acid
anhydride, reacts with an alcohol.
Naming Esters
Propanoate from propanoic acid
H
H3C
O
C
Name :………………………………….
C
…………………………………………..
O
H
C2H5
ethyl from ethanol


The alcohol part comes first as the ………….yl
The carboxylic acid part comes next as the …………..oate
Student activity 3
1. Name each of the following esters
H
O
Name:…………………………………………………………………..
H
C
H
C
O
C3H7
5
H3C
H
H
C
C
H
H
O
O
H
H
C
H
Name:…………………………………………………………………..
C
C3H7
O
Name:…………………………………………………………………..
C
O
C2H5
2. Name the products formed between each of the following carboxylic acids and alcohols
in the presence of sulphuric acid. Draw the full displayed formula for each of the products.
Write a fully balanced equation for each reaction
a) Ethanol and Ethanoic acid
………………………………………………………………………………………………………..
………………………………………………………………………………………………………….
………………………………………………………………………………………………………….
b) Pentan-1-ol and butanoic acid
………………………………………………………………………………………………………….
………………………………………………………………………………………………………….
………………………………………………………………………………………………………….
c) Butan-1-ol and propanoic acid
………………………………………………………………………………………………………….
…………………………………………………………………………………………………………..
…………………………………………………………………………………………………………..
Remember - an anhydride has the functional group shown. When it reacts
with an alcohol R’OH, as well as the ester RCOOR’, we also make a
molecule of carboxylic acid RCOOH.
d) Ethanoic anhydride and propan-1-ol
………………………………………………………………………………………………………….
………………………………………………………………………………………………………….
………………………………………………………………………………………………………….
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e) Propanoic anhydride and methanol
………………………………………………………………………………………………………….
………………………………………………………………………………………………………….
………………………………………………………………………………………………………….
1.
2.
3.
4.
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Reactions of Esters
1. Acid Hydrolysis
Hydrolysis is the reverse of esterification. Esters are unreactive with water and an acid
catalyst is required to catalyse the reaction. Hydrolyis breaks down an ester to produce a
carboxylic acid and an alcohol. It literally means the splitting of water by reaction with the
ester.
Equation for the hydrolysis of propylethanoate.
………………………………………………………………………………………………………..
2. Base Hydrolysis (alkaline hydrolysis)
http://estream.loreto.ac.uk/view.aspx?id=4755~4v~6cmREL7c
The reaction with a base is called saponification (soap making). The reaction cannot be
reversed.
Equation:
………………………………………………………………………………………………………..
Uses of esters
Esters are used as solvents in the chemical industry and as adhesives. Nail varnish
remover and board pens contain ethylethanoate as a solvent. The flavours and fragrances
of different esters are widely used to produce food flavours and perfumes.
Ester
Octyl Ethanoate
flavour
Orange
Methyl benzoate
Marzipan
Methyl butanoate
Pineapple
Ethyl deca-2,4-dienoate
Pears
structure
Extension
Using radioactive oxygen atoms 18O and a Geiger Muller tube, describe how you could
work out whether it is the C-O bond of the acid end of the ester or the O-R’ of the alcohol
end of the ester which breaks during hydrolysis. This should lead you to think about the
mechanism of hydrolysis which involves a nucleophilic attack on the carbonyl carbon.
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Student activity 4
Read the passage below and underline the words which have the following meanings:
a)
b)
c)
d)
e)
a particle which contains covalent bonding;
propane-1,2,3-triol
a carbon with four different groups attached;
a molecule which contains double or multiple bonds;
blood vessels which take blood away from the heart.
Triglycerides, saturated and unsaturated fats
What are triglycerides?
Triglycerides are formed from a single molecule of glycerol, combined with three fatty acids
on each of the OH groups, and make up most of fats digested by humans. Ester bonds form
between each fatty acid and the glycerol molecule.
Below is the general structure of a triglyceride.
How are trans-fatty acids linked to heart disease?
Unsaturated fat is a fat molecule containing one or more double bonds between the carbon
atoms. The process of hydrogenation is intended to add hydrogen atoms to cis-unsaturated
fats, eliminating a double bond and making them more saturated. These saturated fats
have a higher melting point, which makes them attractive for baking and extends their shelflife. However, the process frequently has a side effect that turns some cis-isomers into
trans-unsaturated fats instead of hydrogenating them completely. This is another class trans fats, e.g vaccenic acid, which occurs naturally in trace amounts in meat and dairy
products from ruminants. Unlike other dietary fats, trans fats are not essential, and they do
not promote good health. The consumption of trans fats increases one's risk of coronary
heart disease by raising levels of "bad" LDL (low-density lipoprotein) cholesterol and
lowering levels of "good" HDL (high-density lipoprotein) cholesterol. It is the fact that the
HDLs remove cholesterol from the blood whereas LDLs do not which leads to a build up of
cholesterol in the arteries and their thickening. Health authorities worldwide recommend
that consumption of trans fat be reduced to trace amounts. Trans fats from partially
hydrogenated oils are more harmful than naturally occurring oils.
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Cardiovascular disease involves the heart or blood vessels (arteries and veins). While the
term technically refers to any disease that affects the cardiovascular system, it is usually
used to refer to those related to atherosclerosis (arterial disease).
Biodiesel refers to a vegetable oil or animal fat based diesel fuel consisting of long-chain
alkyl (methyl, propyl or ethyl) esters. Biodiesel is typically made by chemically-reacting
lipids (e.g., vegetable oil, animal fat (tallow)) and alcohol (or glycerol). These types of fuel
are becoming increasingly important as the world’s reserves of fossil fuels are being
depleted.
Student activity 5
1. Show the triglyceride formed when glycerol reacts with dodecanoic acid (12 C atoms)
2. Show the triglyceride formed from the reaction of oleic acid and glycerol.
|Oleic Acid
3. Label the following as cis or trans.
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4. How might the melting points of the cis and trans (Z and E) isomers of a fatty acid differ?
By looking at their shapes, you should be able to see that trans isomers will be able to pack
closer together so their will be more Vd W forces so the melting points will be higher.
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