Carbonyl compounds Flashcards
Test for carboxylic acids
Add aqueous sodium carbonate = effervescence
Fats and oils are hydrolysed
in acidic solutions and by boiling with sodium hydroxide
Formation of an ester 1
Carboxylic acid + alcohol
Catalyst used in the formation of esters 1
Strong acid
Another catalyst used in the formation of esters 1
Sodium hydroxide
When sodium hydroxide is used
The salt of the acid and water is produced rather than just the acid itself. But the reaction goes to completion
Acylation
process by which the acyl group is introduced to another molecule
How readily the reaction occurs depends on three factors:
- The magnitude of the δ positive charge on the carbonyl carbon, which in turn depends on the electron releasing or attracting power of Z
- How easily Z is lost
- How good the nucleophile is
Mechanism of the reaction of acylating agents and nucleophiles
Addition Elimination reaction
Ethanoic anhydride is manufactured on a large scale. Its advantages over ethanoyl chloride as an acylating agent are:
- Cheaper
- Less corrosive
- Does not react with water readily
- Safer, as the by-product of its reaction is ethanoic acid rather than hydrogen chloride
Suggest one reason why Tollens’ reagent is used as the oxidising agent in the specific test
for aldehydes rather than the less expensive acidified potassium dichromate(VI).
Dichromate(VI) will also oxidise / give a positive test with alcohols
Allow ‘dichromate’.
Allow ‘dichromate(VI) will oxidise other organic molecules /
functional groups’.
In order to ensure that the oxidation to ethanoic acid is complete, the reaction is
carried out under reflux.
Describe what happens when a reaction mixture is refluxed and why it is necessary,
in this case, for complete oxidation to ethanoic acid
A mixture of liquids is heated to boiling point for a prolonged time
Vapour is formed which escapes from the liquid mixture, is changed back into
liquid and returned to the liquid mixture
Any ethanal and ethanol that initially evaporates can then be oxidised
