Alcohols: Oxidation of Alcohols

Question 1

What makes an alcohol primary?

Answer 1

• C bonded to OH is only bonded to 1 other C atom

Question 2

What makes an alcohol secondary?

Answer 2

• C bonded to OH is bonded to 2 other C atoms

Question 3

What makes an alcohol tertiary?

Answer 3

• C bonded to OH is bonded to 3 other C atoms

Question 4

What type of organic compounds can primary alcohols be oxidised into?

Answer 4

• Can be oxidised into aldehydes by distillation

- Primary alcohols can be further oxidised into carboxylic acids under reflux

Question 5

How can primary alcohols be oxidised into aldehydes?

Answer 5

• Gently heat primary alcohol (e.g ethanol) with potassium dichromate (VI) solution and sulfuric acid in a test tube
• Aldehyde is distilled off immediately to avoid further oxidation

Question 6

What apparatus would be used to oxidise primary alcohols into aldehydes?

Answer 6

• Fractionating column
• Thermometer
• Condenser
• Beaker to contain liquid

Question 7

How can primary alcohols be oxidised into carboxylic acids?

Answer 7

• Alcohol (e.g ethanol) is mixed with excess oxidising agent and heated under reflux
• Aldehyde stays in reaction mixture and is oxidised to carboxylic acid

Question 8

What apparatus would be used to oxidise primary alcohols into carboxylic acids?

Answer 8

• Round bottomed flask

- Liebig condenser (water in at bottom, water out at top)

Question 9

What type of organic compounds can secondary alcohols be oxidised into?

Answer 9

• Can be oxidised into ketones under reflux

Question 10

How can secondary alcohols be oxidised into ketones?

Answer 10

• Refluxing a secondary alcohol with acidified potassium dichromate (VI) will produce a ketone

Question 11

What does heating under reflux mean?

Answer 11

• Heating under reflux - can increase temperature of organic reaction to boiling without losing volatile reactants or products
• Any vapourised compounds are cooled, condense and drip back into reaction mixture

Question 12

Can tertiary alcohols be oxidised?

Answer 12

• In tertiary alcohols there are no hydrogen atoms attached to the carbon bonded to the OH group.
• Therefore, tertiary alcohols cannot be easily oxidised (except under extreme conditions, when C–C bonds are broken)
• Cannot be oxidised with potassium dichromate (VI), can be oxidised by burning