Liebermann nitroso reaction

Certain phenols give the Liebermann Nitroso Reaction. 

Lassaigne test, 1039, 1040 defects in, 1043 Lead dioxide, 199 Lead tetracetate, 199, 951 Lessing rings, 92 Leuckart reaction, 561, 567 Liebermann nitroso reaction, 649 Light petroleum, purification of, 174 Ligroin, 174 Linseed oil, 445... 

The formation of Af-nitrosamines which usually separate as orange-yellow oils or low melting solids indicates the presence of a secondary amine. Confirm the formation of the nitrosamine by the Liebermann nitroso reaction. This consists in warming the nitrosamine with phenol and concentrated sulphuric acid. The sulphuric acid liberates nitrous acid from the nitrosamine, and the nitrous acid reacts with the phenol to form p-nitrosophenol, which then combines with another molecule of phenol to give red indophenol. In alkaline solution the red indophenol yields a blue indophenol anion. 

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. 

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 a nitroso reaction Section IV,100,(v). Tertiary aromatic amines, of the type of dimethylaniline, yield p-nitroso derivatives see Section IV,100,(vii). ... 

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-... 

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. 

The Uebermann Test The Liebermann test, also known as the liebermann nitroso test (Figure 7.17), is another presumptive test that incorporates a coupling reaction... 

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. 

---