Sunday, December 9, 2007

TMH Ch. 34 Exercises in Organic Chemistry

Practical organic chemistry:

JEE Syllabus

Detection of elements (N, S, halogens);
Detection and identification of the following functional groups:
hydroxyl (alcoholic and phenolic),
carbonyl (aldehyde and ketone),
carboxyl, amino and nitro;
Chemical methods of separation of mono-functional organic compounds from binary mixtures.

Detection of Elements (N,S, halogens)

Lassaigne test is used for this.

First sodium extract of the given organic compound is prepared.
A pea sized dry piece of sodium metal (freshly cut) is taken in an ignition tube and the tube is heated to melt the sodium metal piece to shining globule. Then a pinch of the organic compound is introduced in the tube. Then the tube is further heated first gently and strongly till the lower end of the tube becomes red hot. The tube is then plunged and broken in about 20 ml. of distilled water taken in porcelain dish. The solution is boiled for about 5 minutes and filtered. The filtrate obtained is known as sodium extract.

Test for Nitrogen

To 2ml of sodium extract, a little ferrous sulphate is added. The solution is boiled and a little dilute sulphuric acid is added. Appearance of prussian blue or green colouration indicates the presence of nitrogen in the compound.

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