Oxidising alcohols Flashcards
What oxidising agent is used?
Acidified potassium dichromate
What does a primary alcohol oxidise to?
Aldehyde
What does further oxidation of a primary alcohol lead to?
Carboxylic acid
What does a secondary alcohol oxidise to?
Ketone
What does a tertiary alcohol oxidise to?
Dont oxidise
What colour change will occur with acidified potassium dichromate when primary and secondary alcohols are oxidised?
Orange to green
How do you oxidise a primary alcohol to an aldehyde?
Heat alcohol with potassium dichromate solution and sulphuric acid
The aldehyde has a lower boiling temperature than the alcohol so it is distilled off the distillation apparatus first
How do you oxidise primary alcohols to a carboxylic acid?
Oxidise vigorously
Mix with excess oxidising agent and heated under reflux
Aldehyde stays in the reaction mixture and is oxidised to carboxylic acid
What does heating under reflux do?
Heats the temperature of an organic reaction to boiling without losing volatile solvents, reactants or products.
Any vaporised compounds are cooled, condense and drip back into the reaction mixture
What do anti-bumping granules do?
Make boiling smoother
How do you oxidise a secondary alcohol to a ketone?
Heat under reflux
Acidic conditions - acidified potassium dichromate
What colour change will occur when acidified potassium dichromate oxidises tertiary alcohols?
Stays orange
What three oxidising agents can be used to distinguish between aldehydes and ketones?
- Fehlings
- Tollens
- Benedicts
How can you distinguish between aldehydes and ketones using Fehlings?
Add to both
If aldehyde, the colour will change from deep blue to brick red
If ketone, the colour will remain deep blue
How can you distinguish between aldehydes and ketones using Tollen’s reagent?
Add to both
If aldehyde, silver mirror will form
If ketone, it will remain colourless
