Alcohols

Question 1

What is the functional group of an alcohol?

Answer 1

-OH

Question 2

How should you name alcohols?

Answer 2

alkan-?-ol

Question 3

What are 2 uses of ethanol and methanol? (of interest only)

Answer 3

Ethanol:
1 - In alcoholic drinks
2 - As a solvent (e.g. in methylated spirits)

Methanol:
1 - Petrol additive (to improve combustion)
2 - Chemical feedstock to make organic products

Question 4

Name the 2 ways it is possible to make ethanol

Answer 4

1 - Hydration of ethene

2 - Fermentation of sugars

Question 5

What are the reagents used in hydration of ethene?

Answer 5

H20 (g)/steam

use alcohols booklet to see equation of hydration of ethene in displayed formula

Question 6

What are the conditions of hydration of ethene

Answer 6

• Phosphoric acid (H3PO4) catalyst
• High temperature
• High pressure

Question 7

What is the use of ethanol when made from hydration of ethene?

Answer 7

As a solvent and a chemical feedstock

Question 8

What is the atom economy of hydration of ethene? How do you know?

Answer 8

100% atom economy
This is because in the reaction there is only 1 product made and it is useful so 100% of the atoms in the reactants are reacted into the useful product

Question 9

What is the yield of ethanol when made from hydration of ethene?

Answer 9

100% yield (eventually)

Question 10

Where does ethene come from?

Answer 10

Catalytic cracking of crude oil

Question 11

What is the reagent in fermentation of sugars?

Answer 11

Glucose, C6H12O6

Question 12

What must the conditions of fermentation of sugars be?

Answer 12

• Enzyme (in yeast)

- 37 degrees

Question 13

What is the use of ethanol produced from the fermentation of sugars?

Answer 13

in alcoholic drinks

Question 14

What observations can be made from the fermentation of sugars?

Answer 14

Bubbles of gas (from the carbon dioxide produced)

Question 15

What is the atom economy of fermentation of sugars?

Answer 15

51%

Question 16

What is the yield of ethanol from fermentation of sugars?

Answer 16

7-14%

Question 17

How does the solubility of alcohols change when chain length is increased? Why?

Answer 17

Solubility decreases as the chain length increases because:

• A larger part of the molecule is made up of a non-polar hydrocarbon chain
• The hydrocarbon chain does not form hydrogen bonds with water molecules

Question 18

Get a piece of paper and show an illustration of hydrogen bonding between water and ethanol

Answer 18

Check answer on pg 3 of alcohols booklet

Question 19

How does the boiling point of an alcohol and an alkane differ? Why is this?

Answer 19

Alcohols have higher boiling points than alkanes (of similar Mr)
This is because a significant amount of heat energy is needed to overcome the hydrogen bonds in alcohols whereas the intermolecular forces in alkanes are London forces - alcohols have a lower volatility than alkanes

Question 20

What is a primary alcohol?

Answer 20

The -OH group is attached to a carbon with only one alkyl group

Question 21

What is a secondary alcohol?

Answer 21

The -OH group is attached to a carbon with two alkyl groups

Question 22

What is a tertiary alcohol?

Answer 22

The -OH group is attached to a carbon with three alkyl groups

Question 23

What are the reagents in the elimination of H20 from an alcohol?

Answer 23

Concentrated phosphoric acid/sulfuric acid (+ alcohol)

Question 24

What is a dehydration reaction?

Answer 24

A H2O molecule is removed from a saturated molecule (alcohol) to form an unsaturated molecule (alkene)

Question 25

What types of alcohols can be oxidised using an oxidising agent?

Answer 25

Primary and secondary alcohols

Question 26

Which type of alcohol cannot be oxidised?

Answer 26

Tertiary alcohols

Question 27

What is a suitable oxidising agent for alcohols?

Answer 27

Acidified dichromate Cr2O72-/H+

Question 28

What is the symbol for the oxidising agent in an equation?

Answer 28

[O]

Question 29

During the reaction, what colour does the oxidising agent change from?

Answer 29

From orange to green

Question 30

What does partial oxidation of a primary alcohol produce?

Answer 30

Aldehydes

Question 31

What conditions must there be to undergo partial oxidation?

Answer 31

Heat by distillation

Question 32

Why can you not heat under reflux to make an aldehyde?

Answer 32

If possible then heating under reflux will make a carboxylic acid

Question 33

What does further/complete oxidation of a primary alcohol produce?

Answer 33

Carboxylic acids

Question 34

What does the oxidation of secondary alcohols produce?

Answer 34

Ketones

Question 35

What can’t ketones be oxidised?

Answer 35

The carbon attached to the ketone functional group had no hydrogen bonded (to the C=O carbon) so cannot be oxidised

Question 36

Why can’t a tertiary alcohol be oxidised?

Answer 36

Doesn’t have a H atom on the C to which the OH is attached

Question 37

What do alcohols react with to form haloalkanes?

Answer 37

Hydrogen halides

Question 38

What condition is needed to make an alcohol into a haloalkane?

Answer 38

Heat under reflux

Question 39

What reagents are needed to make an alcohol into a haloalkane?

Answer 39

Metal halide and concentrated sulfuric acid (to make hydrogen halide) + alcohol