2.7 Alcohols and Carboxylic Acids

Question 1

State the functional group of alcohols.

Answer 1

Alcohols contain an -OH functional group.

Question 2

State the general formula of alcohols.

Answer 2

follow the general formula CnH2n+1OH

Question 3

What are the two main production methods of alcohols?

Answer 3

Hydration
Fermentation

Question 4

What is hydration?

Answer 4

This method produces alcohols from alkenes in the presence of an acid catalyst.

Question 5

List the conditions for hydration.

Answer 5

Phosphoric acid is commonly used as the catalyst under aqueous conditions at 300 degrees C and high pressures.

Question 6

Why is hydration favoured in industrial processes?

Answer 6

This process has a very high percentage yield as ethanol is the only product. Therefore the hydration method is favoured as an industrial process.

Question 7

Write the equation for hydration of ethene.

Answer 7

Question 8

What is fermentation?

Answer 8

In this process, enzymes break down starch from crops into sugars which can then be fermented and distilled to form alcohol.

Question 9

List the benefits of fermentation.

Answer 9

1. This method is cheaper than hydration as it can be carried out at a lower temperature
2. It is considered to be carbon neutral as the carbon given out when it is burned is equal to the carbon taken in by the crops during the growing process.

Question 10

State the disadvantage of fermentation.

Answer 10

it has to be fermented in batches, meaning it is a much slower process with a lower percentage yield.

Question 11

Write the equation for fermentation.

Answer 11

Question 12

How can alkenes be formed?

Answer 12

By the dehydration of alcohols.

Question 13

What is the dehydration of alcohols?

Answer 13

Alkenes can be formed from the dehydration of alcohols, where a molecule of water is eliminated from the molecule.

In order to do this, concentrated sulfuric acid is used as a catalyst.

CnH2n+1OH → CnH2n + H2O

This reaction means that addition polymers can be produced from fermentation without the need for crude oil, a non-renewable resource.

Fermentation produces the primary alcohol which is then dehydrated to produce an alkene used in the production of addition polymers.

Question 14

What is a primary alcohol?

Answer 14

One where the OH group is joined to one carbon

Question 15

What is a secondary alcohol?

Answer 15

One where the OH group is joined to 2 carbons

Question 16

What is a tertiary alcohol?

Answer 16

One where the OH group is joined to 3 carbons

Question 17

What types of alcohols can be oxidised?

Answer 17

Primary and Secondary alcohols

Question 18

Can tertiary alcohols be easily oxidised?

Answer 18

No

Question 19

How are aldehydes formed?

Answer 19

A primary alcohol, in the presence of a potassium dichromate catalyst, is heated and distilled to form an aldehyde

Question 20

Draw the displayed formula for the formation of aldehydes.

Answer 20

Question 21

How are carboxylic acids formed?

Answer 21

When heated further under reflux conditions, primary alcohols will oxidise further to form carboxylic acids.

Aldehyde produced from primary alcohol will oxidise further to form carboxylic acids.

Question 22

Draw the displayed formula for the formation of carboxylic acids.

Answer 22

Question 23

How are ketones formed?

Answer 23

When secondary alcohols are heated in the presence of potassium dichromate (VI), they are oxidised to form ketones.

Question 24

Draw the displayed formula for the formation of ketones.

Answer 24

Question 25

How do you test for alcohols?

Answer 25

Potassium dichromate (VI) is used to test for alcohols as it is used as an oxidising agent. If primary or secondary alcohols are present, a colour change from orange to green can be observed. Tertiary alcohols will remain orange as they are not easily oxidised.

Question 26

How do you test for carboxylic acids?

Answer 26

Carboxylic acids act as acids when sodium hydrogencarbonate is added to it, producing CO2 gas. The gas produced can be bubbled through lime water and if CO2 is present, solution turns cloudy.

Question 27

State the functional group of carboxylic acids.

Answer 27

-COOH They have a carbonyl group (C double bond O) and a hydroxyl group - OH

Question 28

Are carboxylic weak acids?

Answer 28

Yes

Question 29

Why are carboxylic acids weak acids?

Answer 29

Because they only slightly dissociate in solution, forming a H+ ion and a carboxylate ion RCOO- ion

Question 30

How do carboxylic acids react with carbonates?

Answer 30

They produce a carboxylate salt, water and CO2

Question 31

Write an equation for the reaction of carboxylic acids with carbonates

Answer 31

Question 32

How do carboxylic acids react with bases?

Answer 32

They produce a carboxylate salt and water

Question 33

Write an equation for the reaction of carboxylic acids with bases

Answer 33

Question 34

Describe the process of esterification.

Answer 34

Carboxylic acids can react with alcohols in the presence of a strong acid catalyst, under reflux, to form esters. Concentrated sulfuric acid is often used as the acid catalyst. These are carbon compounds with a C=O carbonyl group and a C-O-C bond which joins together the two reactants.

Question 35

Write the general eqn for esterification.

Answer 35

Question 36

What are esters?

Answer 36

Sweet smelling compounds often used in food flavourings and perfumes

Question 37

List the properties of esters.

Answer 37

Low boiling points and also make good solvents for other polar molecules

Question 38

Glycerol undergoes esterification ________

Answer 38

to form triglyceride esters

Question 39

What is biodiesel?

Answer 39

ester produced from vegetable oils and methanol in the presence of a strong acid catalyst

Question 40

How can different carbon compounds be separated?

Answer 40

By distillation

Question 41

What is distillation process most useful for?

Answer 41

separation of alcohols and their oxidised forms as they have differing boiling points due to various types of intermolecular forces