Alcohols

Question 1

Give two ways ethanol can be manufactured

Answer 1

Fermentation and hydration of Ethene

Question 2

What occurs in fermentation

Answer 2

Glucose is fermented by yeast and turned into ethanol and carbon dioxide

C6H12O6->2C2H5OH +2CO2

Question 3

Give advantages and disadvantages of fermentation

Answer 3

Advantages
Dosent require much energy
Low tech process
Renewable

Disadvantage
Slow process
Produces mainly impure ethanol
Batch process

Question 4

What happens ins hydration of ethene and give the catalyst used and conditions involved

Answer 4

Water is added to ethene to make ethanol

At 300 degrees 60 atmospheres
H3Po4 catalyst

Question 5

Give advantages of hydration and disadvantages

Answer 5

Advantages
Relatively fast process
Produces pure ethanol
Continuous flow process

Disadvantages
Uses lots of energy
Requires fairly high technology
Non renewable

Question 6

When is ethanol considered a biofuel

Answer 6

When it undergo fermentation and it’s carbon neutral

Question 7

What 3 types of reactions can alcohols undergo

Answer 7

Elimination
Nucleophillic substitution
Oxidation

Question 8

Give 3 types of alcohols

Answer 8

Primary alcohols-2 Hydrogens attached

Secondary alcohols- 1 hydrogen attached

Tertiary- no hydrogen

Question 9

When is alcohols undergo Elimination what is it called and give the conditions involved and what is produced

Answer 9

It’s called dehydration

180 reflux conc sulphuric acid

Alkenes

Question 10

What is produced when a primary alcohol is oxidised

Answer 10

Aldehydes and water

[O]

Question 11

What is produced when an secondary alcohol is oxidised

Answer 11

A ketone and water

Question 12

What is produced when a aldehyde is oxidised further and what else is needed for this too happen

Answer 12

Carboxylic acid is produced reflux 2[O]

Question 13

What is the oxidising agent used in oxidation reactions with alcohols

Answer 13

Potassium dichromate in sulphuric acid

Question 14

What colour change the oxidising agent undergo

Answer 14

It’s goes from orange to green

Question 15

Give two tests used to distinguish between aldehydes and ketones

Answer 15

Feelings solution

Tollens reagent

Question 16

What happens when tollens reagent reacts with aldehydes or ketone

Answer 16

No reaction with ketone

Ia sliver mirror forms when it reacts with aldehyde

Question 17

What happens when fehlings solution react with a aldehyde or ketone

Answer 17

It reduces from blue to red when reacted with an aldehyde

No reaction with ketone

Question 18

Why is air kept out of fermentation vessels

Answer 18

To prevent oxidation of ethanol to ethanoic acid

Question 19

State four essential conditions for fermentation of glucose

Answer 19

Yeast
Absence of water
Temperature of 30-40
Anaerobic conditions

Question 20

State how you would distinguish between a primary alcohol and secondary alcohol/tertiary

Answer 20

Add potassium dichromate

Primary alcohol will cause it to change from orange to green

Secondary alcohol will result in no change

Question 21

What is dehydration and state what is formed and the condtions needed for this reaction

Answer 21

It’s the removal of water from a compound and the condtions are conc H2SO4 at 180

Alkene

Question 22

State how in an experiment a carboxylic acids form

Answer 22

We heat it the aldehyde under reflux

Question 23

What is the mechanism for the formation of an Alkene from alcohol

Answer 23

Elimination conc H2SO4

Question 24

What happens when a reaction mixture its refluxed

Answer 24

A mixture of liquids is heated to boiling point for a long time

Vapours are formed which escape from the liquid mixture and return back

It means any alcohol that initially evaporates is oxidised