Organic Analysis Tests And Mechanisms

Question 1

How do you test for a primary or secondary alcohol?

Answer 1

Add acidified potassium dichromate to test tubes and place the test tubes in warm water. If the solution turns from orange to green, it is a primary or secondary alcohol as the chemicals react to form an aldehyde(1°) or a ketone(2°). Tertiary alcohols don’t react

Question 2

How do you test for an aldehyde or ketone?

Answer 2

Add DNHP and if a yellow, orange or reddish-orange precipitate forms then it’s an aldehyde or ketone

Question 3

How do you distinguish between an aldehyde and a ketone?

Answer 3

Test 1: Add tollen’s reagent and heat for a few minutes. The aldehyde is the compound that forms a silver mirror on the side of the test tube
Test 2: Add Fehling’s solution and heat for a few minutes. The aldehyde is the solution that forms a red precipitate

Question 4

What is the test for alkenes?

Answer 4

Alkenes decolourise bromine water

Question 5

How do you test for a carboxylic acid?

Answer 5

React with a carbonate and if it’s a carboxylic acid, it will effervesce indicating carbon dioxide is being produced

Question 6

What are the conditions for a group/atom to be a leaving group?

Answer 6

It must be attached to an electrophilic carbon, it must be more electronegative than the carbon, it must be positively charged or neutral and its bond enthalpy with the carbon cannot be too high