NITROUS ACID TEST Sample Clauses

NITROUS ACID TEST. Add 0.5 mL or 0.5 g of the amine to 1.5 mL concentrated HCl diluted with 2.5 mL water and cool the solution to 0 oC. Dissolve 0.5 g of sodium nitrite in 2.5 mL water and add this solution dropwise, with shaking, to the cold solution of the amine hydrochloride. Continue the addition until the mixture gives a positive test for nitrous acid. The test is carried out by placing a drop of the solution on starch-iodide paper; a blue color indicates the presence of nitrous acid. If the test is positive, transfer 2 mL of the solution to a clean test tube, warm gently, and examine for evolution of gas. The presence of a primary aliphatic amine is indicated by a rapid bubbling or frothing as the aqueous sodium nitrate is added at 0 oC. Primary aromatic amines from diazonium salt with the evolution of gas only upon warming. The solution from the primary aromatic amine should be subjected further to the coupling reaction as follows: Add 2 mL of the cold diazonium solution to a solution of 0.1 g 2-naphthol in 2 mL 10% sodium hydroxide solution and 5 mL water. The formation of an orange-red dye with the evolution of gas upon warming indicates the presence of a primary aromatic amine. A secondary amine will give a pale-yellow oil or low-melting solid without any evolution of gas. An immediate positive test for nitrous acid (as indicated by the blue color on a starch-iodide paper) with no evolution of gas indicates a tertiary aliphatic amine. Tertiary aromatic amines will react with nitrous acid to produce a dark-orange solution of the C- nitrosoamine hydrochloric salt. Treating 2 mL of this solution with 10% sodium hydroxide or sodium carbonate solution will give a bright-green or blue nitrosoamine base which can be purified and characterized. Perform the above test with propylamine, diethylamine, aniline, N-methylaniline and N,N- dimethylaniline.