Organic Functional Group Tests

Question 1

How to test for an Alkene

Answer 1

1) shake the compound with bromine water in a test tube.

2) if a double bond is present, an addition reaction occurs and the solution will decolourise.

Question 2

How to test for an alcohol

Answer 2

1) add a small amount of the substance to a test tube using a Pipette.

2) add a small amount of the oxidising agent (acidified potassium dichromate) to the test tube.

3) add a stopper to the test tube and shake well

4) place in hot water bath. If primary and secondary alcohol is present, the colour will change from orange to green. If tertiary alcohol present, nothing will happen.

Question 3

How to test for an aldehyde

Answer 3

1) to a test tube containing tollen reagent, add a small sample of the solution and place in a water bath.

2) leave to stand for 5-10 minutes.

3) if an aldehyde is present, a Silver mirror will Form.

Question 4

How to form tollens’ reagent

Answer 4

1) add 0.5 cm3 of silver nitrate.
2) add 1cm3 of sodium hydroxide solution (a brown precipitate is formed)
3) add 2.5 cm3 of ammonia solution. Gently agitate until the brown precipitate dissolves.

Question 5

How to identify a carboxylic acid

Answer 5

1) add the solution to a spotting tile.
2) using a spatula add a small mass of sodium carbonate .
3) if an aldehyde is present, effervescence will be produced. Stop adding sodium carbonate when the bubbling stops.