1. Higher Chemistry Unit 2 – Natures Chemistry
Section 5 - Alcohols, Carboxylic Acids and Esters

2. 2.5 Alcohols, Carboxylic Acids and Esters Learning Intentions
Learning Outcomes/Success Criteria Unit 2 CfE Higher Chemistry
I can name, draw full structural formulae and write shortened structural formulae for alcohols.
I can name, draw full structural formulae and write shortened structural formulae for carboxylic acids.
I can name, draw full structural formulae and write shortened structural formulae for esters.
I can name the functional groups in alcohols, carboxylic acids and esters
I can describe how to prepare an ester
I can name and predict the products produced and vice versa name and predict the esters in the reverse reaction.
I can state describe characteristics and name uses of esters
I can describe how esters are formed in a condensation reaction
I can describe the process of hydrolysis of esters and predict the products of this.

3. Uses of Alcohols
Ethanol can be produced on a large scale by catalytic hydration of ethene.
This ethanol can be used as a fuel solvents, making medicines, printing inks and cosmetic products.

4. What makes a molecule an Alcohol?
The chemical structure of an alcohol can be obtained by replacing one of the hydrogen atoms of an alkane with an –OH group, the hydroxyl functional group as shown below.
ethane

5. Shortened Structural Formula Full Structural Formula
Alcohols
Alcohol
(Carbon Atoms)
Molecular Formula
Shortened Structural Formula
Full Structural Formula
Boiling
Point
Methanol
(1)
CH3OH
Ethanol
(2)
C2H5OH
CH3CH2OH
Propanol
(3)
C3H7OH
CH3CH2CH2OH

6. Shortened Structural Formula Full Structural Formula
Alcohols
Alcohol
(Carbon Atoms)
Molecular Formula
Shortened Structural Formula
Full Structural Formula
Butanol
(4)
C4H9OH
CH3CH2CH2CH2OH
Pentanol
(5)
C5H11OH
CH3CH2CH2CH2CH2OH
Hexanol
(6)
C6H13OH
CH3CH2CH2CH2CH2CH2OH

7. Alcohol General Formula
The number of Hydrogen atoms = 2 times the number of Carbon atoms plus 1 plus OH on the end
General Formula for alcohols is CnH2n+1OH

8. What are Isomers?
Isomers have the same molecular formula but different structural formula.

9. Questions Draw the full structural formula of:
Hexan-2-ol
Pentan-2-ol
Draw as many isomers of hexan-2-ol

10. What makes a molecule a Carboxylic Acid?
The chemical structure of a carboxylic acid can be obtained by removing all of the hydrogen atoms of an alkane and replacing it with the carboxyl functional group - COOH as shown below.
ethane
Ethanoic Acid

11. Shortened Structural Formula Full Structural Formula
Carboxylic Acids
Carboxylic acid
(Carbon Atoms)
Molecular Formula
Shortened Structural Formula
Full Structural Formula
Methanoic Acid
(1)
HCOOH
Ethanoic Acid
(2)
CH3COOH
Propanoic Acid
(3)
C2H5COOH
CH3CH2COOH

12. Shortened Structural Formula Full Structural Formula
Carboxylic Acids
Carboxylic acid
(Carbon Atoms)
Molecular Formula
Shortened Structural Formula
Full Structural Formula
Butanoic Acid
(4)
C3H7COOH
CH3CH2CH2 COOH
Pentanoic Acid
(5)
C4H9COOH
CH3CH2CH2CH2COOH
Hexanoic Acid
(6)
C5H11COOH
CH3CH2CH2CH2CH2COOH

13. Carboxylic Acid General Formula
The number of Hydrogen atoms = 2 times the number of Carbon atoms plus 1 plus COOH on the end
General Formula for carboxylic acids is CnH2n+1COOH

14. Learning Check Give names of the following: A. CH3COOH|
B. CH3CHCOOH
ethanoic acid (acetic acid)
2-methylpropanoic acid

15. Organic Chemistry
Originally, chemical compounds were divided into 2 classes:
Inorganic or Organic
Organic compounds were derived from living things. It
was believed that they contained a ‘vital force’ and could
not be made from inorganic compounds (non-living sources).
Organic chemistry is the study of carbon compounds

16. Organic Chemistry
Organic chemistry is basically the study of compounds containing carbon (with the exclusion of oxides and carbonates).
There are so many compounds containing carbon that a whole branch of chemistry is devoted to their study.
Organic molecules may be as simple as methane, CH4 HO
or as complicated as cholesterol

17. Esters

18. Esters Esterification, Alkanoic acids reacting with Alkanols.
Alcohol Carboxylic Acid  Ester + Water H+
Esters have sweet smells and are more volatile than carboxylic acids.
They are responsible for sweet fruit smells.
280 aromas make up a strawberry smell!!
3-methylbutyl ethanoate in bananas.
2-aminobenzoate is found in grapes.
We imitate these smells by manufacturing flavourings.
Esters are also used in perfumes.
Esters can also be used as solvents in glues.
Polyesters are used to make plasticisers.
Methyl ester is a biodiesel.

19. Naming Esters R-OH + R’-COOH  R’-COOR + Water ethyl propanoate R-yl
R’-oate
First, the 1st word comes from
the alcohol. The name ends in –yl.
Second, find the C=O in the
carboxylate group, this gives the
2nd word with the ending –oate.
This comes from the acid.
Second
First
C2H5 C O
CH3 CH2 COO CH2 CH3
Naming carboxylic acids and esters
Advice from the BBC on naming organic compounds.
ethyl propanoate

20. Learning Check
Give the name of the following compound, which is responsible for the flavour and odour of pears. O 
CH3 — C—O —CH2CH2CH3
propyl ethanoate

21. Naming esters. A B C D
The ester in box D is made from ………………………… and …………………………………. acid
and is called …………………………………………………
ethylmethanoate?
Which box shows
propylethanoate?
methylethanoate?
Box B
Box A
Box C
methanol
propanoic
methylpropanoate

22. Making Esters
One way of preparing esters is to condense an alcohol with a carboxylic acid:
The reaction is slow at room temperature and the yield of ester is low. The rate can be increased by heating the reaction mixture and by using concentrated sulphuric acid as a catalyst. The presence of the concentrated sulphuric acid also increases the yield of ester.
The aim of this experiment is to prepare an ester and to identify some of the characteristic properties of esters.

23. Ester formation Condensation Reaction + + CH3OH CH3COOH +
Ester link H O + + R H O R C O H
CH3OH
CH3COOH +
ethanoic acid
methanol
CH3COOCH H20
methyl ethanoate
The reaction is brought about by heating a mixture of a carboxylic acid
and an alcohol with a little concentrated sulphuric acid. (which acts as a
Catalyst and absorbs the water produced).

24. Making esters Procedure
Decide which alcohol and carboxylic acid you need to make each ester in the table.
1. Before collecting the alcohol and carboxylic acid set up a water bath using the larger beaker and heat the water until it boils. Turn off the Bunsen.
2. Add the alcohol to a test tube to a depth of about 1 cm. To this add about the same volume of carboxylic acid. If the acid is a solid then use a spatulaful.
3.In the interests of safety your teacher/lecturer may carry out the next step.
Add about 5 drops of concentrated sulphuric acid to the reaction mixture.

25. Making esters
4. Soak the paper towel in cold water, fold it up and wrap it round the neck of the test tube. Secure it with a rubber band. This arrangement acts as a condenser when the reaction mixture is being heated.
5. Place a loose plug of cotton wool in the mouth of the test tube. This will contain any chemicals which may spurt out of the reaction mixture when it is heated.
6.Place the test tube in the hot water bath

26. Making esters
7. While the reaction mixture is being heated add about 20 cm3 of sodium hydrogencarbonate solution to the small beaker.
8. After about 10 minutes, take the test tube from the water bath and remove the plug of cotton wool. Slowly pour the reaction mixture into the sodium hydrogencarbonate solution. This neutralises the sulphuric acid and any remaining carboxylic acid and so removes the smell of the carboxylic acid.
9. Gently swirl the contents of the beaker and look to see if there is any sign of the ester separating from the aqueous mixture.
10. To smell the ester with your nose at least 30 cm from the mouth of the beaker gently waft the vapour towards your nose and take just a sniff.

28. Uses of esters Esters are also used as non-polar industrial solvents.
Esters are oily liquids with generally very pleasant fruity smells and have a range of uses.
Many esters are used as flavourings and in perfumes.
Natural fruit flavours contain subtle blends of some of the esters in the table below:
Name
Shortened Structural Formula
Odour/Flavour
CH3(CH2)4CH3
Banana
CH3(CH)7CH3
Methyl Butanoate
Pineapple
3-Methylbutyl Butanoate
CH3(CH2)2(CH2)2CH(CH3)2
Apple
CH3COOC3H7
Pear
Methyl-1-butyl ethanoate
CH3COOCH(CH3)C4H9
2-Methylpropyl methanoate
Raspberry
C3H7COOC5H11
Apricot, Strawberry
Benzyl ethanoate
CH3COOCH2C6H5
Peach, flowers
Ethyl methanoate
Methyl 2-aminobenzoate
C6H4(NH2)COOCH3
Grapes
Benzyl butanoate
C3H7COOCH2C6H5
Cherry
Esters are also used as non-polar industrial solvents.

29. Uses of esters Factors affecting perfume design e.g. using esters:
Designing a perfume - several issues to address by way of design factors.
The perfume needs to be a mixture of compounds to give a prolonged perfumery effect.
The perfumer chemist has to design the mixture to give a particular fragrance which includes ...
 the top note - the first fragrant molecule to be released,
and the low note, the last molecule to be vapourised.

30. Uses of esters Esters are also used as non-polar industrial solvents.
Some of the smaller esters are quite volatile and are used as solvents in adhesives, inks and paints – pentyl ethanoate is used in nail varnish for example.

31. Uses of esters
Ethyl ethanoate is one of a number of solvents used to extract caffeine from coffee and tea.
De-caffeinated products produced with ethyl ethanoate are often described on the packaging as "naturally decaffeinated" because ethyl ethanoate is a chemical found naturally in many fruits.

32. Uses of esters
Caffeine (C8H10N4O2) is an example of a class of compounds called alkaloids which are produced by plants.
The name alkaloid means “alkali-like”, where alkali is a base and hence refers to these basic properties.
Carryout the experiment to extract caffeine from tea.

33. Uses of esters
Caffeine is more soluble in the organic solvent ethyl ethanoate than in water, so we will extract caffeine into the organic solvent to separate it from glucose, tannins, and other water soluble compounds using a separating funnel.
The ethyl ethanoate portions can be combined and the ethyl ethanoate removed by evaporation to leave the caffeine .

34. Hydrolysis of Esters Alcohol + Carboxylic Acid  Ester + Water
Condensation
Alcohol Carboxylic Acid  Ester + Water
Hydrolysis
Alcohol Carboxylic Acid  Ester + Water
The ester is split up by the chemical action of water, hydrolysis.
The hydrolysis and formation of an ester is a reversible reaction. R C O H +
Bonds broken
Ester + Water + R C O H
Bonds formed
Carboxylic Acid + Alcohol

35. Learning Check Draw the structure of the following compounds:
3-bromobutanoic acid
Ethyl propanoate Br |
CH3CHCH2COOH

36. Learning Check
Write the equation for the reaction of propanoic acid and methanol in the presence of an acid catalyst.
O O
 H 
CH3CH2COH HOCH3 CH3CH2COCH H2O

37. Name the compound below
Butyl butanoate

38. Learning Check
What are the organic products when methyl ethanoate reacts with
A. Water and an acid catalyst?
B. KOH? O 
CH3COH HOCH3 O 
CH3CO– K HOCH3

39. Percentage yields
CH3COOH + CH3CH2CH2OH <=> CH3COOCH2CH2CH3 + H2O
4.3 g of propyl ethanoate was produced when 6 g of ethanoic
acid was reacted with propan-1-ol.
What is the percentage yield of the ester?
Percentage yield = actual yield/theoretical yield x 100%