Liebermann’s reaction

Formation of nitrosaminey RgN NO. (a) From monomethylaniline. Dissolve I ml. of monomethylaniline in about 3 ml. of dil. HCl and add sodium nitrite solution gradually with shaking until the yellow oil separates out at the bottom of the solution. Transfer completely to a smdl separating-funnel, add about 20 ml. of ether and sh e. Run off the lower layer and wash the ethereal extract first with water, then with dil. NaOH solution, and finally with w ter to free it completely from nitrous acid. Evaporate the ether in a basin over a previously warmed water-bath, in a fume cupboard with no flames near. Apply Liebermann s reaction to the residual oil (p. 340). 

Liebermann s reaction. Most phenols that have a position para to a hydroxyl group free, respond to this test. Heat a crystal of the phenol with a crystal of sodium nitrite in a dry test-tube for 20 sec. Cool and add 1 ml of concentrated sulphuric add. An intense green-blue colour is produced, which changes to red when the mixture is poured carefully into an excess of water, and becomes blue when the solution is made alkaline. 

Aromatic tertiary nitroso compounds and compounds containing an —NO group bound to oxygen or nitrogen liberate nitrous acid under the influence of cone, sulfuric acid. In the presence of phenols Liebermann s reaction takes place (p. 195). Free nitrous acid can also be detected on the basis of its reaction with diphenylamine. The latter reaction is also given by nitroesters. 

Reaction of Diphenylnitrosoamine. Carry out Liebermann s Nitroso Reaction as described for phenol (p. 340), but use about 0 05 g. of the nitrosamine instead of the one crystal of sodium nitrite, and finally add only 3-4 drops of sulphuric acid. The deep greenish-blue colour is obtained, becoming red on dilution and reverting to blue on being made alkaline. 

Reactions, (i) ) >-Nitrosodimethyianiline docs not give Liebermann s Nitroso Reaction with phenol and sulphuric acid (see footnote, p. 340). 

Dissolve 1 g. of the secondary amine in 3-5 ml. of dilute hydrochloric acid or of alcohol (in the latter case, add 1 ml. of concentrated hydrochloric acid). Cool to about 5° and add 4-5 ml. of 10 per cent, sodium nitrite solution, and allow to stand for 5 minutes. Add 10 ml. of water, transfer to a small separatory funnel and extract the oil with about 20 ml. of ether. Wash the ethereal extract successively with water, dilute sodium hydroxide solution and water. Remove the ether on a previously warmed water bath no flames should be present in the vicinity. Apply Liebermann s nitroso reaction to the residual oil or solid thus. Place 1 drop or 0 01-0 02 g. of the nitroso compovmd in a dry test-tube, add 0 05 g. of phenol and warm together for 20 seconds cool, and add 1 ml. of concentrated sulphuric acid. An intense green (or greenish-blue) colouration will be developed, which changes to pale red upon pouring into 30-50 ml. of cold water the colour becomes deep blue or green upon adding excess of sodium hydroxide solution. 

The p-nitroso compounds do not give Liebermann s nitroso reaction. 

The presence of a nitmso-coinpound may be detected as follows. Melt together a niiniite quantity of nitrosophenol and a few crystals of [ilienol. Add ahout 2 c.c. concentrated sulphuric acid and waiin ciy gently. A blue solution is obtained, which changes to red on dilution with water, and back to blue on adding alkali (Liebermann s nitioso reaction sec Reaction, p. 180). Sec AppL Hiiix, ]). 280. 

The action of bromine water (p. 180), Liebermann s nitroso-reaction (p. 180) and the phenolphthalein reaction (p. 186), using rone, sulphuric acid or zinc chloride, may also be applied. 

In the case of a secondary base, the above treatmemt with hydrochloric acid and sodium nitrite will give an insoluble nitrosaminc (licpiid or solid), which is frcc(ueutly 3 cllow. It may be separated by ether tind, after removing the ether, tested l y Liebermann s nitroso-reaction (sec Reaction 3, p. 159). Niti Sus. acid has no action on tertiary aliphatic amines, hut fornrs nitroso-... 

Some reference to the use of nitrous acid merits mention here. Primary aromatic amines yield diazonium compounds, which may be coupled with phenols to yield highly-coloured azo dyes (see Section IV, 100,(iii)). Secondary aromatic amines afford nitroso compounds, which give Liebermann s nitroso reaction Section IV,100,(v). Tertiary aromatic amines, of the type of dimethylaniline, yield p-nitroso derivatives see Section IV,100,(vii). ... 

Liebermann s Nitroso Reaction.—When phenol in sulphuric acid, phenyl sulphuric acid, is treated with a nitrite or with nitroso amine a daj k green, red or brown color is obtained which changes to blue or green on addition of an alkali. The test is known as Liebermann s nitroso reaction, and may be used in testing for a phenoly a nitrite or a nitroso amine. 

A part of the specimen N-93 was extracted with chloroform, and a glycoside fi action (S-chf) was obtained. The residue was extracted with methanol. For the reference, the chloroform extracts of the roots of C. caudatum and C. wilfordii were prepared and named A-chf and B-chf, respectively. All the chloroform extracts, S-chf, A-chf and B-chf, gave positive Keller-Kiliani reaction and Liebermann-Burchard reaction, showing the presence of 2,6-dideoxysugar and steroidal skeleton in their structures, respectively. However, the HPTLC pattern of S-chf on a silica gel plate developed by CHCl3-Me0H-H20 (65 35 10, lower layer) was different fi om those of A-chf and B-chf (Fig. 1)... 

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