Alcohols

Question 1

Naming OH groups as side chain

Answer 1

2-hydroxyethanenitrile

2-hydroxyethylamine

Question 2

Aldehyde

Answer 2

RCHO
e.g. ethanal, propanal

Question 3

Ketone

Answer 3

RCOR
e.g. propanone, pentan-2-one

Question 4

Carboxylic Acid

Answer 4

RCOOH
e.g ethanoic acid, propanoic acid

Question 5

Classification

Answer 5

Question 6

Producing ethanol

Answer 6

Key reaction: anaerobic respiration
Reaction name: fermentation
C6H12O6(aq) → 2CH3CH2OH(aq) + 2CO2
Conditions: yeast enzymes, temp 35℃, no O2

No O2 as ethanol formed may oxidise to ethanoic acid

Question 7

Hydration of ethene advantages and disadvantages

Answer 7

advantages:
large scale production method, high purity product made

disadvantage:
high temp/ pressure needed increasing cost, crude oil is non-renewable

Question 8

Fermentation

Answer 8

advantages:
uses renewable sources, low cost

disadvantages:
slow RoR, impure ethanol made needs distilling

Question 9

Biofuels

Answer 9

advantages:
considered carbon neutral, come from renewable raw materials

disadvantages:
many other carbon costs in production, so not carbon neutral ( CO2 released during transport), food prices rise as crops used for biofuels

Question 10

Elimination reaction

Answer 10

reaction name: dehydration
CH3CH2OH → CH2=CH2 + H2O
conditions: hot conc. H2SO4

Question 11

Oxidation of Primary Alcohols to an Aldehyde

Answer 11

Reagent: Acidified K2Cr2O7
Observations: Orange → Green
Conditions: Heat under distillation

Question 12

Oxidation of Aldehyde to a Carboxylic Acid

Answer 12

Reagent: Acidified K2Cr2O7
Conditions: Heat under reflux

Question 13

Oxidation of Primary Alcohols to a Carboxylic Acid

Answer 13

Reagent: Acidified K2Cr2O7
Observations: Orange → Green
Conditions: Heat under reflux, excess oxidising agent

Question 14

Oxidation of Secondary Alcohols to a Ketone

Answer 14

Reagent: Acidified K2Cr2O7
Observations: Orange → Green
Conditions: Heat under reflux or distillation

Question 15

What type of alcohol cannot be oxidised?

Answer 15

tertiary

Question 16

Oxidation of propane-1,2,3- triol under distillation and reflux

Answer 16

Question 17

Distillation

Answer 17

• turn water supply on to condenser
• heat flask
• use thermometer to maintain temp at BP of ethanal
• ethanol vapours condense back to liquid in condenser
• ethanol collected in cooled container to avoid vaporising

Question 18

Reflux

Answer 18

• connect condenser vertically and turn on water supply on
• heat flask
• ethanal will form by oxidation and will vaporise
• ethanal will condense on side of condenser and fall back into reaction container
• ethanal will oxidise again to form ethanoic acid

Question 19

Why is reflux used to oxidise a primary alcohol to a carboxylic acid?

Answer 19

• Reflux doesn’t allow any reactant vapour to escape

Question 20

What happens to the aldehyde as it is produced during distillation?

Answer 20

• The aldehyde forms as a vapour and escapes from the reaction mixture into the condenser

Question 21

Why is distillation used when producing an aldehyde from a primary alcohol?

Answer 21

• Distillation allows the aldehyde to escape the reaction mixture and prevents further oxidation

Question 22

Ethanol can be oxidised to ethanal or ethanoic acid. Describe how ethanal can be made in high yield, as opposed to ethanoic acid

Answer 22

• Use distillation
• Heat at the boiling point of ethanal
• Collect ethanal as it is distilled off

Question 23

Silver mirror test

Answer 23

reagent- tollen’s reagent
condition- warm gently
aldehyde- silver mirror forms
ketone- NVC

Question 24

Fehlings test

Answer 24

reagent- fehlings solution
condition- warm gently
aldehyde- blue solution to brick red ppt
ketone- NVC

Question 25

Test for carboxylic acid

Answer 25

reagent- sodium carbonate (Na2CO3)
condition- room temp
observation- effervescence