PRACTICAL5 

AIM :- To detect the presence of unknown Halogens (like Cl,Br,I) in a given organic compound 'B'.

Materials Required :-

given organic compound Na piece ferrous sulphate dil.sulphuric aciddil.acetic acidlead acetatedil.nitric acid  silver nitrate ignition tube burner wire gaugechina dish filter paper funnel glass rodtest tubes AgNO3 solution 

Concentrated sulphuric acid

CHCl₃ or CCl₄ or CS₂

Theory :-

The detection of extra elements in organic compounds is crucial in its investigation. Carbon is included in all organic molecules. Hydrogen is also found in most organic molecules (the few exceptions are the compounds such as CCl₄, CS₂, etc.). Other elements included in organic molecules include oxygen, nitrogen, sulfur, and halogens, in addition to carbon and hydrogen.Because virtually all organic substances include carbon and hydrogen, procedures to identify them are frequently unnecessary, and their existence may be presumed without testing. The tests for detecting nitrogen, sulfur, and halogens will be discussed here.? What is the Lassaigne’s Test, and how does it work ?Lassaigne’s test can identify nitrogen, sulfur, and halogens organic molecules. A little bit of Na metal is heated with the organic compound in a fusion tube.The idea is that Na changes all of the elements present into ionic form.Na + C + N → NaCN2Na + S → Na₂SNa + X → NaX ( X= Cl, Br, or I)By boiling the fused mixture with distilled water, the produced ionic salts are removed. Sodium fusion extract is called Lassaigne’s Test

Halogen Testing

For the halogens test, the sodium fusion extract is first acidified with HNO₃ and then treated with AgNO₃ . The appearance of a white precipitate soluble in NH₄OH signifies the presence of Cl. A yellowish precipitate sparingly soluble in NH₄OH maybe Br and while a yellow precipitate insoluble in NH₄OH maybe I.

AgNO₃ + NaX → AgX ↓ + NaNO₃

Confirmatory Test for Br and I  (Layer Test)

 Layer's test is the test that is used to detect in the presence of 'bromide' and 'iodide ions' in a compound.(To be performed if the AgNO₃ test is positive and doesn't show White precipitate. )For the layer test, the sodium fusion extract is first treated with CHCl₃ or CCl₄ or CS₂ and then slowly along the sides of test tube Concentrated sulphuric acid is added .If this gives an yellowish orangish colour layer Br is confirmed whereas if a violet colour is formed I is confirmed in the compound. 

Procedure:-

Preparation of sodium Fusion Extract for Lassaigne's Test:

1. Firstly, take a little piece of sodium metal in the ignition tube and tape it a bit to make the metal settle down in the tube.

2. Heat the ignition tube until sodium metal  becomes circular in shape.

3. Put 1 pinch of compound in the tube and gently heat it .Heat it for 2 minutes continously.

 4. Now, take 20 ml of distilled water in the china dish and place the tube in the china dish. 

5. Do the same process for 4-5 times.

6. Crush the tube and heat it to let the water evaporate into half of the quantity.

7. Then filter it to remove the insoluble materials. Lassaigne's extract is the name given to filtrate.

Observation:-

violet colour was observed after the Layer's Test.

Result:-

VIOLET colour is observed thus presence of IODINE is confirmed

Precautions:-

1. Safety: Wear appropriate personal protective equipment, such as gloves and goggles, to protect yourself from any potential hazards.2. Handling sodium: Sodium is a highly reactive metal that reacts violently with water. Handle sodium with caution, using dry forceps or spatula, and keep it away from moisture.3. Fusion process: Carefully add a small amount of the organic compound to the fusion tube, followed by a small piece of sodium metal. Avoid adding excessive amounts of sodium, as it may lead to violent reactions.4. Heating: Heat the fusion tube gently and gradually to avoid any sudden reactions or splattering. Use a Bunsen burner or a heating mantle for controlled heating.