Sulphonamides benzene

Choice of solvent for recrystallisation. Obtain small samples (about 0 5 g.) of the following compounds from the storeroom (i) salicylic acid, (Li) acetanilide, (iii) m-dinitrobenzene, (iv) naphthalene, and (v) p-toluene-sulphonamide. Use the following solvents distilled water, methylated spirit, rectified spirit, acetone, benzene and glacial acetic acid. 

Amine B.P. M.P < 20 Benzene- sulphonamide />-Toluene- sulphonamide Phenyl- thiourea ot-Naphthyl- thiourea Picrate A-Substltuted Phthallmlde Benzamide... 

The following give abnormal results when treated with chlorosulphonio acid alone, preferably at 50° for 30-60 minutes —fluobenzene (4 4 -difluorodiplienyl-sulphone, m.p. 98°) j iodobenzene (4 4 -di-iododiphenylsulplione, m.p. 202°) o-diclilorobenzene (3 4 3. -4 -tetrachlorodiphenylsulphone, m.p. 176°) and o-dibromobenzene (3 4 3 4 -tetrabromodiphenylsulphone, m.p. 176-177°). The resulting sulphones may be crystallised from glacial acetic acid, benzene or alcohol, and are satisfactory for identification of the original aryl halide. In some cases sulphones accompany the sulphonyl chloride they are readily separated from the final sulphonamide by their insolubility in cold 6N sodium hydroxide solution the sulphonamides dissolve readily and are reprecipitated by 6iV hydrochloric acid. 

Procedure 1. Dissolve 1 g. of the compound in 5 ml. of chloroform in a test-tube and cool in ice. Add 5 ml. of chlorosulphonic acid CA UTION in handhng) dropwise and with shaking. When the initial evolution of hydrogen chloride subsides, remove the reaction mixture from the ice and, after 20 minutes, pour it into a 50 ml. beaker filled with crushed ice. Separate the chloroform layer, wash it well with water, and evaporate the solvent. Recrystallise the residual aryl sulphonyl chloride from light petroleum (b.p. 40-60°), chloroform or benzene this is not essential for conversion into the sulphonamide. 

Sulphonamides. Mix together 1 0 g. of the dry acid or 1 - 2 g. of the anhydrous salt with 2 5 g. of phosphorus pentachloride f and heat under a reflux condenser in an oil bath at 150° for 30 minutes. Cool the mixture, add 20 ml. of dry benzene, warm on a steam bath and stir the solid mass well to extract the sulphonyl chloride filter. Add the benzene solution slowly and with stirring to 10 ml. of concentrated ammonia solution. If the sulphonamide precipitates, separate it by filtration if no solid is obtained, evaporate the benzene on a steam bath. Wash the sulphonamide with a little cold water, and recrystallise from water, aqueous ethanol or ethanol to constant m.p. 

The rate of decomposition of benzenesulphonyl azide to benzene-sulphonamide is said to be accelerated appreciably by thiophenol 18> in a radical-catalyzed process probably not involving a free nitrene intermediate. 

The success of this reaction was ascribed to the solubility of the chlorozinc intermediate, whereas other chloramine-T derivatives (e.g. the sodium salt) are insoluble. An alternative non-nitrene pathway was not eliminated from consideration. On the other hand, no aromatic substitution or addition, characteristic of a free sulphonyl nitrene (see below), took place on treatment of jV,lV-dichloromethanesulphonamides with zinc powder in benzene in the cold or on heating. The only product isolated was that of hydrogen-abstraction, methanesulphonamide 42>, which appears to be more characteristic of the behaviour of a sulphonyl nitrene-metal complex 36,37). Photolysis of iV.iV-dichloromethanesulphonamide, or dichloramine-B, or dichloramine-T in benzene solution led to the formation of some unsubstituted sulphonamide and some chlorobenzene but no product of addition of a nitrene to benzene 19>. 

On Sulphonyl Chlorides and Sulphonamides.—The conversion of benzenesulphonic acid into its chloride and amide shows that derivatives of sulphonic acids, analogous to those of carboxylic acids, can be obtained. The sulpho-chlorides are much less reactive than are the chlorides of the carboxylic acids benzene sulphochloride, for example, can be dis-stilled in steam almost without decomposition. 

It has been shown that the thermolysis of arenesulphonyl azides with benzene to yield A-arenesuIphonylazepines (44-80%) is aided by the addition of Adogen [30], Sulphonylazepines have also been obtained from the reaction of tetra-n-butylammo-nium salts of sulphonamides with benzene in the presence of xenon difluoride the reaction probably proceeds via the intermediate nitrene [31 ]. 

Mixtures of primary, secondary and tertiary amines can usually be separated by Hinsberg s method. This is based on the fact that reaction with benzene-sulphonyl (or toluene-p-sulphonyl) chloride converts primary amines into alkali-soluble sulphonamides, secondary amines into alkali-insoluble sulphon-amides and leaves tertiary amines unaffected. 

Although ylides coming from sulphonamides can be obtained through the above general method, an alternative procedure has been developed using (dimethoxyiodo)benzene. 

Iodosylbenzene (1.1 g, 5 mmol) was stirred for 15 min in methanol (40 ml), under nitrogen. About 3 g of powdered Linde 3A molecular sieves were added (heated previously at 400°C and 0.01 torr for 15 h) and the suspension was stirred in a capped Schlenk tube for 2 h. The molecular sieves were removed and the drying process was repeated with a fresh portion of molecular sieves. A small loss of iodosylbenzene (44 mg) was indicated by iodometric titration. To the filtrate, after removal of the solid phase, was added the sulphonamide (1 g, 4.95 mmol) portionwise the solution turned yellow and a precipitate separated. After concentration to a small volume, dichloromethane (5 ml) was added and the solid mass was collected, washed with dichloromethane and dried affording [(2-nitrophenylsulpho-nylimino)iodo]benzene (1.8 g, 92%), as an amorphous powder, decomposing on heating. 

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