RP 6 - Organic tests

Question 1

How do you test for an alcohol?

Answer 1

1) Add 1cm3 of alcohol to a test tube, add a small piece of sodium.
2) Presence of alcohol is indicated by white precipitate and effervescence

Question 2

How do you distinguish between different alcohol types?

Answer 2

1) Heat under reflux with acidified potassium dichromate.
2) Primary and secondary alcohols will be oxidised shown by a colour change from orange to green
3) Tertiary alcohols cannot be oxidised and will remain orange

Question 3

How do you test for an aldehyde?

Answer 3

1) Add fehling’s solution to the sample
2) If an aldehyde is present, a red precipitate will form

Question 4

How do you test for an alkene (unsaturation)?

Answer 4

1) Add bromine water to the sample.
2) If an alkene is present the bromine water will decolourise.

Question 5

How do you test for a carboxylic acid?

Answer 5

1) Add sodium carbonate to the sample.
2) If a carboxylic acid is present, carbon dioxide will be given off.

Question 6

How do you test for a haloalkane?

Answer 6

1) Add five drops of haloalkane to about 1 cm³ of sodium hydroxide solution in a test tube.
2) Warm the contents of the test tube at 60°C for a few minutes.
3) Then add 2 cm³ of dilute nitric acid and 1 cm³ of silver nitrate solution.
4) If a halo alkane is present a precipitate forms, the colour of the precipitate that forms depends on the halide ion present in solution:
- White = chloride ions
- Cream = bromide ions
- Yellow = iodide ions