Tests for Amines – MeitY OLabs

Tests for Amines – MeitY OLabs


Tests for Amines Amines are derivatives of ammonia in which
one or more hydrogen atoms are replaced by alkyl or aryl groups. When one of the three
hydrogen atoms is replaced by alkyl or aryl group, primary amine is formed. When two of
the three hydrogen atoms are replaced by alkyl or aryl group, secondary anime is formed.
When all the three hydrogen atoms are replaced by alkyl or aryl substituents, tertiary amine
is formed. Nicotine, present in tobacco leaves, and caffeine,
present in seeds of coffee plants, are amine containing compounds.
Our aim here is to identify amines using some simple tests. They are: Solubility test
Litmus test Azo – dye test
Nitrous acid test Hinsberg Test Solubility test Materials required: Organic compound, dilute hydrochloric acid
and dropper. Procedure: Take a small quantity of dilute hydrochloric
acid using the dropper. Add it to the test tube containing organic
compound. Shake the test tube well.
Amines have appreciable basicity, so they dissolve in mineral acids. Litmus test Materials required: Organic compound, moist red litmus paper and
dropper. Procedure: Take a small quantity of organic compound
using a dropper. Put 1 or 2 drops of the compound onto the
moist red litmus paper. Amines turn red litmus blue, indicating it
is basic in nature. Azo-dye test Materials required: Organic compound, sodium nitrite, beta-naphthol,
distilled water, dilute hydrochloric acid, dilute sodium hydroxide, ice cold water, test
tubes and droppers. Procedure: Take small quantities of organic compound,
sodium nitrite and beta-naphthol in tests tubes A, B and C respectively.
Using a dropper, add a small quantity of dilute hydrochloric acid to test tube A.
Shake the test tube well to dissolve the compound in hydrochloric acid.
Now, add a small quantity of distilled water to test tube B.
Shake the test tube well to dissolve sodium nitrite in distilled water to get sodium nitrite
solution. Using another dropper, add a small quantity
of dilute sodium hydroxide solution to test tube C.
Shake the test tube well to dissolve beta-naphthol in dilute sodium hydroxide solution.
Cool the test tubes in a beaker containing ice cold water for some time.
Now, add sodium nitrite solution to the organic compound.
Primary amine, on reaction with nitrous acid formed from sodium nitrite and hydrochloric
acid, gives diazonium salt. Then, add the resulting solution to test tube
C containing beta-naphthol solution. The diazonium salt undergoes coupling reaction
with beta-naphthol to form a scarlet red coloured compound called azo dye. Nitrous acid test Materials required Primary, secondary and tertiary amines, sodium
nitrite, distilled water, concentrated hydrochloric acid, ice cold water, test tubes, droppers
and spatula. Procedure: Take small quantities of primary, secondary
and tertiary amines in test tubes A, B and C respectively.
Using a spatula, take a small quantity of sodium nitrite in a test tube.
To this add a small quantity of distilled water.
Shake the test tube well to dissolve sodium nitrite in distilled water to get sodium nitrite
solution. Cool the solution in ice cold water for some
time. Now, using a dropper, add a small quantity
of concentrated hydrochloric acid to test tubes A, B and C.
Shake the test tubes well to dissolve the compounds in concentrated hydrochloric acid.
Cool the test tubes in ice cold water for some time.
Now, add sodium nitrite solution to test tubes A, B and C.
In test tube A, primary aliphatic amine reacts with nitrous acid, formed from sodium nitrite
and hydrochloric acid, to produce nitrogen gas which is seen as bubbles.
In test tube B, secondary amine reacts with nitrous acid to form a yellow oily layer of
nitrosamine. In test tube C, tertiary amine reacts with
nitrous acid to form soluble nitrite salts. Hinsberg test Materials required: Primary, secondary and tertiary amines, 25%
sodium hydroxide solution, distilled water, benzene sulphonyl chloride, concentrated hydrochloric
acid, water in a beaker, test tubes and droppers. Procedure: Take small quantities of primary, secondary
and tertiary amines in test tubes A, B and C respectively.
Using a dropper, add a small quantity of 25% sodium hydroxide solution to test tubes A,
B and C. Now, add a small quantity of distilled water
to each test tube. Using another dropper, add a small quantity
of benzene sulphonyl chloride solution to each test tube.
Shake the mixture in each test tube for some time.
Cool the test tubes in a beaker containing water.
Primary amine reacts with sodium hydroxide and benzene sulphonyl chloride to form soluble
sulphonamide salt. Secondary amine reacts with sodium hydroxide
and benzene sulphonyl chloride to form insoluble sulphonamide.
Tertiary amine will not react with benzene sulphonyl chloride, but it is insoluble in
sodium hydoxide. Using a dropper, add a small quantity of concentrated
hydrochloric acid to test tube A. Soluble sulphonamide salt formed will react
with hydrochloric acid to form insoluble sulphonamide. Now, add a small quantity of concentrated
hydrochloric acid to test tube B. The insoluble sulphonamide formed in test
tube B will not react with hydrochloric acid. Finally, add a small quantity of concentrated
hydrochloric acid to test tube C. The insoluble amine reacts with hydrochloric
acid to form soluble ammonium salt. Precautions: Handle the organic compound with proper care.
Handle hydrochloric acid with proper care because it is highly hazardous.

5 thoughts on “Tests for Amines – MeitY OLabs

  1. Could please suggest me a concentration for dilute HCl and NaOH?
    I want practice in the lab again. Tnank you.

Leave a Reply

Your email address will not be published. Required fields are marked *