Amines Hinsberg test

There are complications in applying the Hinsberg test to certain amines containing hydroxyl, nitro and carboxyl groups, e.g., p-N-methylamiiiobenzoic acid CHjNHC.HjCOOH (I 4) may behave in this test as a primary amine (soluble in alkali) so that it is essential to consider the properties of the original compound in conjunction with the results of the test. 

Feebly basic amines, e.g., the nitroanilines, generally react so slowly with benzenesulphonyl chloride that most of the acid chloride is hydrolysed by the aqueous alkali before a reasonable yield of the sulphonamide is produced indeed, o-nitroaniline gives little or no sulphonamide under the conditions of the Hinsberg test. Excellent results are obtained by carrying out the reaction in pyridine solution ... 

The treatment of sulfonyl chlorides with ammonia or amines is the usual way of preparing sulfonamides. Primary amines give N-alkyl sulfonamides, and secondary amines give N,N-dialkyl sulfonamides. The reaction is the basis of the Hinsberg test for distinguishing between primary, secondary, and tertiary amines. N-Alkyl sulfonamides, having an acidic hydrogen, are soluble in alkali, while N,N-dialkyl sulfon-... 

Amines are easily identified because they re readily soluble in dilute acid. Sodium fusion converts the cimine to the cyanide ion, which is detectable by a Vciriety of methods. The ready formation and decomposition of diazonium salts (discussed in the earlier section Reactions with nitrous acid ) leads to the identification of primary amines. The Hinsberg test (see the nearby sidebcir) is useful in identifying amines. 

Though it has largely been replaced by spectroscopic methods, at one time the Hinsberg test was useful in the characterization of amines. The first step in the test was the reaction of the amine with a benzenesulfonyl chloride in base. 

Sulfonylation of amines can be a useful way of differentiating (chemically) between primary, secondary, and tertiary amines by what is known as the Hinsberg test. Primary and secondary amines both react with a sulfonyl chloride, but only the sulfonamide from the primary amines has an N—H hydrogen. The sulfonyl group makes this hydrogen relatively acidic and the sulfonamide therefore dissolves readily in sodium hydroxide solutions. The secondary amine does not give a base-soluble amide, whereas the tertiary amine gives no sulfonamide ... 

The Hinsberg test, which can distinguish primary, secondary, and tertiary amines, is based upon sulfonamide formation. In the Hinsberg test, an amine is reacted with benzene sulfonyl chloride. If a product forms, the amine is either a primary or secondary amine, because tertiary amines do not form stable sulfonamides. If the sulfonamide that forms dissolves in aqueous sodium hydroxide solution, it is a primary amine. If the sulfonamide is insoluble in aqueous sodium hydroxide, it is a secondary amine. The sulfonamide of a primary amine is soluble in an aqueous base because it still possesses an acidic hydrogen on the nitrogen, which can be lost to form a sodium salt. 

Hinsberg test To 0.5 ml of the amine (0.5 g, if solid) in a test tube add 1 ml of benzenesulfonyl chloride and 8 ml of 10% NaOH. Stopper the tube and shake for 3 to 5 min. Remove the stopper and warm the tube while shaking in a hot water bath ( 7CPC) for about 1 min. No reaction is indicative of a 3° amine the amine becomes soluble upon acidification (pH = 2 to 4) with 10% HC1. If a precipitate is present in the alkaline solution, dilute with 5 to 8 ml of H20 and shake. If the precipitate does not dissolve, the original amine is probably a 2° one. If the solution is clear, acidify (pH = 4) with 10% HC1. The formation of a precipitate is indicative of a 1° amine (detection limit, 100 mg compounds tested, C, to C10). 

Amines Diazotization Hinsberg test Solubility in dilute HCI All 1° amines give red azodyes with [i-naphthol Distinguishes between 1°, 2°, and 3° All amines are soluble... 

Section 2 presents the Hinsberg test, a test for distinguishing between primary, secondary, and tertiary amines Section 3 gives procedures for preparation of solid derivatives for melting point characterizations and Section 4 gives spectral characteristics. Apply the procedures to known substances along with the unknown. 

The free amine can be liberated by addition of base and extraction into ether. Following evaporation of the ether the Hinsberg test. Group 1(d), can be applied to determine if the compound is a primary, secondary, or tertiary amine. 

Whether an amine is primary, secondary, or tertiary is best shown by the Hinsberg test. The amine is shaken with benzenesulfonyl chloride in the presence of aqueous potassium hydroxide (Sec. 23.6). Primary and secondary amines form substituted sulfonamides tertiary amines do not—if the test is carried out properly. 

Problem 23.24 The sulfonamides of big primary amines are only partially soluble in aqueous KOH. (a) In the Hinsberg test, what incorrect conclusion might you draw about such an amine (b) How might you modify the procedure to avoid this mistake ... 

Deamination of primary amines. The conversion of primary amines into N-sulfonamides under Schotten-Baumann conditions is the basis for the classical Hinsberg test. Baumgarten et aO have found that N-sulfonamides can be converted into N,N-disulfonimides, usually in high yield, by conversion into the sodium salt (NaH) and subsequent reaction with a sulfonyl chloride in DMF as solvent ... 

It does not react with benzene-sulfonyl chloride/ therefore it is a tertiary amine. This analysis is known as the Hinsberg test ... 

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