18C - organic Synthesis

Question 1

What’s the test for Alkenes

Answer 1

Bromine water
Orange to colourless

KMnO4
Pink to colourless

Question 2

Test for carboxylic acids

Answer 2

Sodium carbonate
Fizzing
CO₂ gas should be produced (turns limewater cloudy)

Question 3

Test for aldehyde

Answer 3

Warm Tollens reagent

Silver mirror forms

Question 4

Test for acyl chlorides

Answer 4

Add water

Steamy fumes of HCl

Question 5

How does recrystallisation work

Answer 5

-dissolve impure solid in minimum of hot solvent
-remove insoluble purities by filtration
-allow solution to cool and form crystals and filter with Büchner funnel
-wash solid with cold solvent
Dry solid

Question 6

Why is a minimum of hot solvent used in recrystallisation

Answer 6

If too much solvent is used then not all crystals would form when solvent cools

Question 7

What is drying

Answer 7

When an organic compound is separated from a reaction mixture by distillation and the dry oil is obtained

Question 8

Test for both Ketones and Aldehydes

Answer 8

2,4 DNP and an orange precipitate should form