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Organic compounds
After the discovery of an organic compound, it undergoes a series of chemical tests to find the elements present in it. The chemical tests to check the presence of some elements like carbon, hydrogen, sulphur, nitrogen and halogens are discussed below.
TEST FOR CARBON AND HYDROGEN
The presence of carbon and hydrogen is tested together by the following test.
Principle: The organic compound is oxidized to convert carbon and hydrogen into carbon dioxide and water respectively.
Procedure: A small amount of organic compound is heated with dry copper (II) oxide nearly in the ratio of 1:3 in a dry test tube. As a result the carbon present in the compound change into carbon dioxide and hydrogen in water. Now, this mixture is allowed to pass through a bulb filled with anhydrous copper sulfate to a container filled with lime water.
Inference: (i) If copper sulfate
turns white to blue, then water is present. Hence, hydrogen is confirmed.
turns white to blue, then water is present. Hence, hydrogen is confirmed.
(ii) If lime water turns milky, then carbon dioxide is present. Hence, carbon is confirmed.
The involved chemical equations are as follows
A TEST FOR NITROGEN, SULPHUR AND HALOGENS
PREPARATION OF SODIUM FUSION EXTRACT FOR LASSAIGNE’S TEST
For the detection of the rest of the elements, first, we need to prepare a sodium fusion extract. This extract can be prepared in the following way:
(i) Heat a freshly cut piece of sodium metal in a fusion tube.
(ii) Add a small quantity of organic compound into fusion tube and heat strongly till red hot.
(iii) Plunge this red hot tube in a china dish containing distilled water.
(iv) The fusion tubes break as a result and then boil this mixture for some time.
(v) Filter the solution. The filtrate is called sodium fusion extract or lassaigne’s extract.
The involved chemical equations for detection of sulphur are as follows
The involved chemical equations for detection of nitrogen and sulphur are as follows
The involved chemical equations for detection for nitrogen are as follows
