Liebermann test

NOTE In the nitroso compound literature, frequent reference is made to the Liebermann test. This test may very well have been one for identifying phenols by the dyes which are formed in the presence of nitrous acid. 

Since many, but not all, C-nitroso and A-nitroso compounds are decomposed by concentrated sulfuric acid to give nitrous acid, the Liebermann test has been used frequently to demonstrate the presence of a nitroso group. 

N-(Phenyl-p-arsinic acid) - nitrosoglycineamide, AsO OH)2. CgH4.N(NO).CHa.CO.NH2. is obtained from the sodium. salt of N-(phenyI-jp-arsinic acid )-glyeineaniide by the action of sodium nitrite and hydrochloric acid. It crystallises in rosettes and sheaves of silky needles, becoming yellow at 180° C. and melting at 182° to 188° C. It is readily soluble in hot acetic add, and dissolves to an almost colourless solution in sulphuric acid, which solution gives a brownish-red Liebermann test. 

Liebermann test A presumptive test sometimes used for cocaine and morphine. 

A soln. of N,N -dimethyl-N,N -dinitroso6xamide in methanol added dropwise with stirring and cooling to a mixture of cyclohexanone, K-carbonate, Na-sulfate, and methanol, the product isolated after 1 hr. when the Liebermann test is negative cycloheptanone. Y 71.5%. Also prepn. of diazomethane, as gas and in soln., as well as other diazoalkanes, by adding an ethereal soln. of N,N -dialkyl-N.N -dinitroso6xamide to a soln. of Na in butanol, s. H. Reimlin-ger, B. 94, 2547 (1961) prepn. of diazomethane from bis-(N-methyl-N-nitroso)-terephthalamide cf. J. A. Moore and D. E. Reed, Org. Synth. 47, 16 (1961) from N-methyl-N-nitrosourethan cf. P. Gourtot, Bl. 1962, 1493. 

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... 

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. 

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-... 

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... 

K. Liebermann s Reagent is prepd by mixing phenol with coned sulfuric acid. The test consists in warming a small amt of the unknown substance with few drops of the reagent and observing the color produced. Aromatic nitroso compds and aliphatic nitroso- and isonitroso compds produce a red color which, turns blue... 

Nitroso-0-selenopyrine is obtained when nitrous gases are passed into an ice-cold hydrochloric acid solution of the selenopyrine. It forms dark green crystals, melting without decomposition at 117 5° C., readily soluble in ether, chloroform, alcohol or ethyl acetate, insoluble in water or dilute acids. It responds to Liebermann s nitroso test. 

In addition, many odier tests described on pp. 129-147 may be used for pesticides, especially Aromat-icity (Method 2), Diphenylamine Test, Fujiwara Test, Koppanyi-Zwikker Test, Liebermann s Test, Marquis Test, Methanolic Potassium Hydroxide, Palladiiun Chloride, Sodium Nihoprusside (Method 2), md Sulphuric Acid. Certain pesticides are included in die Tables of colours, where appropriate. A test for the presence of cholinesterase inhibitors... 

Strong Acid Fraction Aromaticity Ferric Chloride Folin-Ciocalteu Reagent Liebermann s Test Millon s Reagent Nessler s Reagent... 

Neutral Fraction Aromaticity Furfuraldehyde Koppanyi-Zwikker Test Liebermann s Test Mercurous Nitrate Nessler s Reagent... 

Forrest Reagent FPN Reagent Liebermann s Test Mandelin s Test Marquis Test Nessler s Reagent Sulphuric Acid... 

Indications. When interpreting the result of this test, account should be taken of the colour given by Sulphuric Acid and by Liebermann s Test. Hydrochlorides give a red colour with this reagent. When the colours differ from those given with Sulphuric... 

Colour Tests. Liebermann s Test—brown Mandelin s Test— green — blue. 

Colour Tests. Ferric Chloride—brown Folin-Ciocalteu Reagent—blue Liebermann s Test—black Millon s Reagent— pink— red. 

Colour Tests. Liebermann s Test—red Mandelin s Test— brown-violet Marquis Test—red Sulphuric Acid—orange. 

Colour Tests. Liebermann s Test—orange Mandelin s Test— grey-green Marquis Test—orange-red. 

Colour Test. Liebermann s Test—brown-orange. 

Colour Tests. Aromaticity (Method 2)—yellow/red Liebermann s Test (100°)—blue. 

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