Carbonyls And Carboxylic Acids

Question 1

How to test for carbonyl group in ketones and aldehydes

Answer 1

1. Add 5cm of 2,4-DNP to test tube in excess
2. Pipette in 3 drops of soloution and leave to stand
3. if no crystals form add sulfuric acid
4. Yellow/ornage ppt indicated aldegydeor ketone

Question 2

How to make up tollems reagent?

Answer 2

1. AgNO3 then add NaOH (aq) until brown ppt formed to make Ag2O
2. Add dilute NH3 until ppt dissolves to be colourless

Question 3

How to test for aldehydes?

Answer 3

1. Add equal maoint of tollens agent to soloution
2. Leave to stand in warm water
3. Silver mirror indicates aldehyde as Ag^+ reduced to Ag(s) formimg silver precipitate and aldehyde oxidised to carboxylic adic