Organic Tests

Question 1

How to test for alkenes

Answer 1

Add bromine water and substance to test tube
Shake
+ = orange -> colourless
- = stays orange

Question 2

How to test for haloalkanes

Answer 2

Add 5 drops of substance 
Add 1cm3 of ethanol 
Add 1cm3 aqueous silver nitrate 
Put In water bath 
\+ = 
chloro = white precipitate 
Bromo = cream precipitate 
Iodo = yellow precipitate

Question 3

How to test for phenols

Answer 3

Testing using a strong base (any acid inc phenol will react)
1. Add naoh
+ = naoh solid dissolves and its colourless
- = no change

Testing with a weak base (phenol won’t react)
1. Add Na2CO3
+ = no reaction
- = effervescence

Question 4

How to test for carboxylic acid

Answer 4

Add Na2CO3
Bubble gas through limewater
+ = solution will fizz and the CO2 produced turns the limewater cloudy
- = nothing happens

Question 5

How to test for carbonyl groups

Answer 5

Dissolve 0.2g of 2,4-DNP in 1cm sulfuric acid, 2cm of water, 5cm methanol = Brady’s reagent
Add 5cm of unknown sol to 2cm of Brady’s
Shake
+ = orange precipitate
- = nothing happens

Crystallise precipitate and compare mp to data base

Question 6

How to test for aldehydes

Answer 6

Make tollens reagent

1. Silver nitrate
2. Sodium hydroxide
3. Add ammonia

Put in hot water bath
Add unknown solution to tolléns

\+ = silver mirror
- = no change

Question 7

How to test for primary and secondary alcohols

Answer 7

Add Acidified potassium dichromate
Warm in hot water bath
Primary and green = orange -> green
Tertiary = nothing