1 of 15
© Boardworks Ltd 2010
What are esters?
Esters are carboxylic acid derivatives with
the hydrogen of the hydroxyl group replaced
by an alkyl group (hydrocarbon chain)
or an aryl group (an aromatic ring).
ethyl ethanoate
(contains an alkyl
group)
2 of 15
methyl benzoate
(contains an aryl
group)
© Boardworks Ltd 2010
Esterification
3 of 15
© Boardworks Ltd 2010
Naming esters
The names of esters are based on the carboxylic acid and
alcohol from which they are produced.
The first component of this ester
name, the methyl, is derived
from the alcohol methanol.
methylethanoate
The second component of the name,
the ethanoate, is derived from the
carboxylic acid ethanoic acid.
ethylmethanoate
propylethanoate
ethanol + methanoic acid
propanol + ethanoic acid
4 of 15
© Boardworks Ltd 2010
Naming esters
5 of 15
© Boardworks Ltd 2010
Hydrolysis of esters
6 of 15
© Boardworks Ltd 2010
Uses of esters
Shorter chain esters have fruity smells and tastes, which
makes them useful as solvents in perfumes and flavourings.
For example, ethyl butanoate smells of
pineapple; pentyl ethanoate smells of pears,
and octyl ethanoate smells of oranges.
Esters are used as artificial
fragrances and flavours as
synthesizing the ester is
often cheaper than extraction
from the natural source.
7 of 15
© Boardworks Ltd 2010
Uses of esters
Esters are also useful as
glues, such as those used for
constructing plastic model
aircraft kits, and as plasticizers
to increase the flexibility of
plastics.
Esters have low boiling points and evaporate readily. This
makes them useful as industrial solvents, for example in paints.
Ethyl ethanoate is one such common solvent, being used in
the decaffeination of tea, as well as a laboratory solvent for
chromatography.
8 of 15
© Boardworks Ltd 2010
Esters in fats and oils
9 of 15
© Boardworks Ltd 2010
Naming fatty acids
Fatty acids have systematic names as well as common names.
For example, the systematic name for oleic acid is octadec-9enoic acid. Some common fatty acids are explained below.
Common
Formula and systematic name
name
stearic
acid
palmitic
acid
oleic
acid
linoleic
acid
10 of 15
CH3(CH2)16COOH
(octadecanoic acid)
CH3(CH2)14COOH
(hexadecanoic acid)
CH3(CH2)7CH═CH(CH2)7COOH
(octadec-9-enoic acid)
CH3(CH2)4(CH═CHCH2)2(CH2)6COOH
(octadec-9,12-dienoic acid)
Description
saturated, found in
most animal fats
saturated, used for
making soaps
monounsaturated, found
in most fats and olive oil
polyunsaturated, found
in vegetable oils
© Boardworks Ltd 2010
Saturated and unsaturated
11 of 15
© Boardworks Ltd 2010
Esters: true or false?
12 of 15
© Boardworks Ltd 2010
TRANS-ESTERIFICATION
• ONE ESTER CONVERTED INTO
ANOTHER ESTER
RCO-OR’ + R’’OH
RCO-OR’’ + R’OH
different alkoxy group
13 of 15
© Boardworks Ltd 2010
Trans fats and health
Most naturally occurring isomers of unsaturated fatty acids are
the cis form, such as cis-octadec-9-enoic acid, found in olive
oil, avocados and nuts.
In the partial hydrogenation of vegetable oils, the trans form of
the fatty acid, such as trans-octadec-9-enoic acid, may be
formed.
A diet high in trans fats, along with saturated fats, can lead to
an increased risk of coronary heart disease (CHD).
14 of 15
© Boardworks Ltd 2010
Cholesterol and lipoproteins
Cholesterol is a lipid that regulates
fluidity in cell membranes. It is
transported in lipoproteins.
Low-density lipoprotein (LDL) transports
cholesterol from the liver to body tissues,
depositing it on the walls of blood vessels.
It increases the risk of CHD.
A diet high in saturated/trans fats is the biggest cause of high
LDL cholesterol levels.
High-density lipoprotein (HDL) transports cholesterol away
from the tissues to the liver, where cholesterol is metabolized.
High HDL levels are linked to a lower risk of CHD.
15 of 15
© Boardworks Ltd 2010
Making soap and biodiesel
16 of 15
© Boardworks Ltd 2010
SOAPS
• Mixture of animal fat and coconut palm oil;
• If mainly animal fat
Less soluble
Longer lasting
• If mainly palm oil
More soluble
Lather quickly
Wash away quickly
**antioxidants added to stop soap and air combining
to make irritant chamicals**
17 of 15
© Boardworks Ltd 2010