List of organic compounds for analysis: · Part 2

  llic silver (Silver mirror) R COONH + H O + 3NH  Tollen’s reagent preparation: Tollen’s reagent is ammoniacal silver nitrate. It is prepared as follows. About g of silver nitrate crystals are dissolved in distilled water in a clean dry test tube. To this aqueous solution of silver nitrate, add ml of dilute NaOH solution to it. A brown precipitate of silver oxide is formed. This precipitate is dissolved by adding dilute ammonia solution drop wise. . Fehling’s Test Fehling’s solution A is an aqueous solution of copper sulphate. Fehling’s solution B is a clear solution of sodium potassium tartrate (Rochelle salt) and strong alkali (NaOH). The Fehling’s solution is obtained by mixing equal volumes of both Fehling’s solution A and Fehling’s solution B that has a deep blue colour. In Fehling’s solution, copper (II) ions form a complex with tartrate ions in alkali. Aldehydes reduces the Cu(II) ions in the Fehling’s solution to red precipitate of cuprous oxide(copper (I) oxide). RCHO + 2Cu OH Aldehyde Fehling's solution (Cuprous ox Cu O  ide) (Red colour) RCOO 3H O Note: Benzaldehyde may not give this test as the reaction is very slow. organic organic - - - - . Sodium nitroprusside Test The anion of the ketone formed by a alkali reacts with nitroprusside ion to form a red coloured complex.this test is not given by aldehydes. CH COCH CH COCH H O [Fe CN NO] sodium nitro prus   OH side (Red coloured com CH COCH [Fe CN NO.CH COCH ]   plex) . Azo-Dye Test This test is given by aromatic primary amines. Aromatic primary amines react with nitrous acid to form diazonium salts. These diazonium salts undergo coupling reaction with β-naphthol to form orange coloured azo dye. NH aniline + HNO + HCl N N benzenediazonium chloride Cl N N benzenediazonium chloride Cl OH β -naphthol HO N N Azo dye (Orange red ) C . Biuret test On strong heating diamide (like urea) forms biuret, which forms