Hinsberg test for

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-... 

What observations would be made for the Hinsberg test for each of the following amines ... 

Karaman, R. Leader, H. Goldblum, A. Breuer, E. Chem. Irui. (London), 1987, 857. 2046For directions for performing and interpreting the Hinsberg test, see Gambill, C.R. ... 

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). 

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. 

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 ... 

Sulfonamide formation is the basis for a chemical test, called the Hinsberg test, that can be used to demonstrate whether an amine is primary, secondary, or tertiary. 

A Hinsberg test involves two steps. First, a mixture containing a small amount of the amine and benzenesulfonyl chloride is shaken with excess potassium hydroxide. Next, after allowing time for a reaction to take place, the mixture is acidified. Each type of amine—primary, secondary, or tertiary—gives a different set of visible results after each of these two stages of the test. 

Amines are characterized by their basicity and, thus, by their ability to dissolve in dilute aqueous acid (Sections 20.3A, 20.3E). Moist pH paper can be used to test for the presence of an amine functional group in an unknown compound. If the compound is an amine, the pH paper shows the presence of a base. The unknown amine can then readily be classified as 1°, 2°, or 3° by IR spectroscopy (see below). Primary, secondary, and tertiary amines can also be distinguished from each other on the basis of the Hinsberg test (Section 20.9A). Primary aromatic amines are often detected through diazonium salt formation and subsequent coupling with 2-naphthol to form a brightly colored azo dye (Section 20.8). 

A traditional method for classifying amines is the Hinsberg test. A discussion of this test can be found in the comprehensive textbooks listed prior to Section 52A. We have found that infrared spectroscopy is a more reliable method for distinguishing between primary, secondary, and tertiary amines. 

Two common qualitative tests for amines are the Hinsberg test and the nitrous acid test. The nitrous acid test is not included here because the N-nitroso derivatives of some secondary amines are carcinogenic. The risk of producing an as-yet-unrecognized carcinogenic material in this procedure outweighs any possible benefit of a test that can also be misleading and difficult to interpret. The modified sodium nitroprusside test has been included as an alternative. 

The procedure for the Hinsberg test must be followed as closely as possible, because it is designed to minimize compHcations that arise because of side reactions that may occur between tertiary amines and benzenesulfonyl chloride. For example, 23, the initial adduct between the chloride and the amine, is subject to an S[,j2 reaction (Secs. 14.2 and 14.4) with another molecule of amine to produce the benzenesulfonamide of a secondary amine and a quaternary ammonium salt (Eq. 25.54). Although this process is normally unimportant, particularly when excess amine is avoided, the observation of small amounts of an insoluble product formed by this pathway may erroneously cause designation of a tertiary amine as secondary. 

To summarize the discussion, tertiary amines may produce small amounts of insoluble products if the concentration of the amine in the test solution is too high and if the reaction time is too long. If the directions of the procedure are followed and care is taken not to interpret small amounts of insoluble product as a positive test for secondary amines, the Hinsberg test may be used with confidence to designate an amine as primary, secondary, or tertiary. 

B. Benzenesuifonamides. The method for preparing the benzenesulfonamides is discussed with the Hinsberg test (Sec. 25.14A). The derivatives may be prepared using that method, but sufficient amounts of material should be used so that the final product may be purified by recrystallization from 95% ethanol. If the derivative is obtained as an oil. it maybe induced to crystallize by scratching at the liquid-liquid or air-liquid interface with a stirring rod. If the oil cannot be made to crystallize, separate it. dissolve it in a minimum quantity of hot ethanol, and allow the solution to cool. Note that some amines do not give solid benzenesulfonamide derivatives. 

In reference to the Hinsberg test used to distinguish between primaiy, secondary, and tertiary amines (see Chapter 9), primary amines yield a sulfonamide that is soluble in aqueous sodium hydroxide, whereas secondary amines give a sulfonamide that is not soluble in this reagent. Offer an explanation for this observation. 

A classical method of distinguishing between the types of amines is based on the difference in the reactivity of amines with benzenesulfonyl chloride followed by reaction vyith sodium hydroxide. The procedure is called the Hinsberg test. First, benzenesulfonyl chloride is shaken with a mixture of an amine and aqueous base. Then, the reaction mixture is examined to determine which of three possible events occurred. If the amine was tertiary, no precipitate appears, and there is no evidence of any reaction. If the amine was secondary, a water-insoluble sulfonamide forms and appears as a precipitate. Primary amines also give no evidence of a reaction because the sulfonamide is soluble in the base, but if the solution is neutralized with an acid, the neutral water-insoluble sulfonamide precipitates. Thus, the experimental results are unique for each class of amine. Infrared spectroscopy and NMR allow us to identify classes of amines (Section 23.14). 

The results of the Hinsberg test indicate that compound W is a tertiary amine. The H NMR provides evidence for the following ... 

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