Pyrroles, color test

Pictet and Rotschy (259) and later Noga (261) described a base which they obtained from an aqueous extract of tobacco and named nicoteine. It is a colorless oil, b.p. 266-267°, miscible with water and soluble in ether, [ ]d 46.41°. It forms a dihydrochloride which is amorphous and has [ Id 8.27°, a chloroplatinate, which does not melt at 280°, an aurichloride which is discolored at 150° and melts at 180° (dec) and a picrate, m.p. 165°. It was assigned the formula C10H12N2. On oxidation, it yields nicotinic acid and its acid solution shows a pyrrole color test. As it has the empirical formula of dihydronicotyrine and it is identical neither with the dihydro-... 

Color test for pyrroles. One drop of an aqueous, ethereal, or alkaline test solution is mixed on a spot plate with one or two drops of a 5% solution of p-dimethylamino-benzaldehyde. If pyrrole or a substance capable of forming pyrrole is present, a violet color will appear. The aldehyde condenses with a tautomeric form of pyrrole (3) to give (4), which is converted by hydrogen ion into the colored quinonoid ion... 

The pyridine used must be free of pyrrole since as little as 0.001% of pyrrole will markedly decrease the yield. The checkers found it most satisfactory to use spectroquality pyridine supplied by Matheson, Coleman and Bell. The submitters purified their pyridine by distillation from potassium hydroxide. To test for the presence of pyrrole, a 0.5-ml. sample of pyridine is diluted with 2.5 ml. of water, and 2 ml. of concentrated hydrochloric acid is added followed by 0.5 ml. of a 5% solution of -dimethyl-aminobenzaldehyde in dilute hydrochloric acid (1 10 dilution of concentrated hydrochloric acid). If pyrrole is present, a red-purple color appears. Spectroquality pyridine gives a negative result in this test. 

Color reactions Boric acid (hydroxyquinones). Dimethylaminobenzaldehyde (pyrroles). Ferric chloride (enols, phenols). Haloform test. Phenylhydrazine (Porter-Silber reaction). Sulfoacetic acid (Liebermann-Burchard test). Tetranitromethane (unsaturation). Condensation catalysts /3-Alanine. Ammonium acetate (formate). Ammonium nitrate. Benzyltrimethylammonium chloride. Boric acid. Boron trilluoride. Calcium hydride. Cesium fluoride. Glycine. Ion-exchange resins. Lead oxide. Lithium amide. Mercuric cyanide. 3-Methyl-l-ethyl-2-phosphoiene-l-oxlde. 3-Methyl-1-phenyi-3-phoipholene-1-oxide. Oxalic acid. Perchloric acid. Piperidine. Potaiaium r-butoxIde. Potassium fluoride. Potassium... 

When the ammonium salt of saccharic acid or of mucic acid is heated, pyrrole is formed (SECTION 658). The latter imparts a carmine-red coloration to a pine-wood shaving which has been moistened with hydrochloric acid. Test the mucic acid obtained in this way as follows Mix 0.1 gram of the acid with 2 cc. of ammonia and evaporate to dryness. Heat the residue strongly in a test-tube during the heating suspend in the tube a soft pine splinter which has been soaked in concentrated hydrochloric acid for a minute or two. 

The first observation on the reactions of glycosylamines with 3-dicarbonyl compounds is due to Elson and Morgan, who found that D-glucosylamine and 2,4-pentanedione, when heated in slightly alkaline solution, give a positive Ehrlich pyrrole test. They considered that 3-acetyl-2-methyl-4-(D-ara6wo-tetrahydroxybutyl)pyrrole (20) was formed and was responsible for the color reaction. 

Initial qualitative evidence that copolymer 54, which contains both calix[4]pyrrole and crown ether subunits, could extract chloride salts into organic media came from a visual test involving a water-soluble dye, 57, that contains a chloride counteranion. Treatment of an aqueous solution of the dye (25.5 mM) with a CH2CI2 solution of copolymer 54 (effective concentration of the calix[4]pyrrole and crown ether repeat units was 1.56 and 1.22 mm, respectively) resulted in a colored organic phase. 

Procedure. A drop of a 6 % solution of ferric chloride and 7 drops of syrupy phosphoric acid are added to a drop of the test solution. The mixture is well stirred, A drop of the pyrrole reagent is then added and the mixture stirred again. A green-blue color indicates the presence of selenious acid. A blank test should be carried out when small amounts of selenious acid are suspected. 

I Ehrlich test is the coupling, in the cold, of p-dimethylaminoben dehyde in hydrochloric acid solution with a free a>potition of a pyrrole, ft Zinc salts are formed in alcoholic solution with zinc acetate. In some cases, oxidation with iodine, denoted by (It), is required to form a colored sine complex. Overoxidation produces green fluorescing compounds... 

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