Organic test tube reactions: Alkenes, Alcohols and Esters

Question 1

describe the test tube test for alkenes

Answer 1

• in a fume cupboard add about 1cm^3 of cyclohexane
• add 5 drops of bromine water
• stopper the tube and shake gently
• two layers will form if an alkene is present

Question 2

describe the test where you use acidified dichromate to oxidise alcohols

Answer 2

• label a test tube primary and add ethanol, label a test tube secondary and add propan-2-ol, label a test tube tertiary and add 2-methylpropan-2-ol
• to each add dilute sulphuric acid, then 10 drops of acidified dichromate and swirl gently
• leave in a warm water bath and observe colour changes
• the primary and secondary should change to a green colour, tertiary will remain orange

Question 3

describe the test tube test where you can make an ester

Answer 3

• add pentan-1-ol to a test tube
• add glacial ethanoic acid to this
• carefully add 5 drops of sulphuric acid
• leave in a warm water bath
• fill a beaker with 50cm^3 of sodium carbonate solution
• add warm test tube contents and cautiously smell
• if an ester has formed it should smell fruity