Benzenesulphonyl chloride

Preparation of Benzenesulphonyl Chloride (SECTION 473).—Convert all of the salt of benzenesulphonic acid obtained in experiment 173 above into benzenesulphonyl chloride as follows HOOD. Place the dry salt in a flask and add phosphorus pentachloride, which should be weighed in the hood, in the proportion of 3 parts by weight of the salt to 4 parts by weight of the chloride. Heat the mixture on the steam-bath, with occasional shaking, for half an hour. Cool, and add to the liquid about ten times its volume of ice-water. Shake about every 10 minutes in order to facilitate the reaction of the phosphorus oxychloride present with water. At the end of an hour 

The chloride can be used without further purification for the experiments given below. If it is desired to preserve the chloride for future use (see experiment 186, page 157), it should be taken up in ether, dried over calcium chloride and distilled under reduced pressure ( 24, page 15) after the ether has been removed. 

Benzenesulphonyl chloride is a colorless liquid which distils at 246°-247° with decomposition, and undecomposed at 120° under a pressure of 10 mm. It melts at 14.5°. 

Method 1. Equip a 1 litre three-necked flask (or bolt-head flask) with a separatory funnel, a mechanical stirrer (Fig. II, 7, 10), a thermometer (with bulb within 2 cm. of the bottom) and an exit tube leading to a gas absorption device (Fig. II, 8, 1, c). Place 700 g. (400 ml.) of chloro-sulphonic acid in the flask and add slowly, with stirring, 156 g. (176 ml.) of pure benzene (1) maintain the temperature between 20 and 25° by immersing the flask in cold water, if necessary. After the addition is complete (about 2 5 hours), stir the mixture for 1 hour, and then pour it on to 1500 g. of crushed ice. Add 200 ml. of carbon tetrachloride, stir, and separate the oil as soon as possible (otherwise appreciable hydrolysis occurs) extract the aqueous layer with 100 ml. of carbon tetrachloride. Wash the combined extracts with dilute sodium carbonate solution, distO off most of the solvent under atmospheric pressure (2), and distil the residue under reduced pressure. Collect the benzenesulphonyl chloride at 118-120°/15 mm. it solidifies to a colourless sohd, m.p. 13-14°, when cooled in ice. The yield is 270 g. A small amount (10-20 g.) of diphenylsulphone, b.p. 225°/10 mm., m.p. 128°, remains in the flask. 

Method 2. Place 90 g. of sodium benzenesulphonate (Section IV.29) (previously dried at 130-140° for 3 hours) and 50 g. of powdered phosphorus pentacliloride (1) in a 500 ml. round-bottomed flask furnished with a reflux condenser heat the mixture in an oil bath at 170-180° for 12-15 hours. Every 3 hours remove the flask from the oil bath, allow to cool for 15-20 minutes, stopper and shake thoroughly until the mass becomes pasty. At the end of the heating period, allow the reaction mixture to cool. Pour on to 1 kilo of crushed ice. Extract the crude benzenesulphonyl chloride with 150 ml. of carbon tetrachloride and the aqueous layer with 75 ml. of the same solvent. Remove the solvent under atmospheric pressure and proceed as in Method 1. The yield is about 170 g., but depends upon the purity of the original sodium benzenesulphonate. 

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The acidic properties of sulphonamides and their mono-substitution derivatives are particularly well illustrated in the alkyl ubstitution compounds, which by reason of these properties can be prepared by two distinct methods. Thus mono- and di-ethylamine, when subjected to the Schotten-Baumann reaction using benzenesulphonyl chloride, gi e benzenesulphonethylamide, and bcnzenesulphondiethylamide respectively. These compounds can also... 

Although benzenesulphonyl chloride has for simplicity been used in the above discussion, tolucne-/>- sulphonyl chloride, CHaCeH SO Cl, is more frequently used in the laboratory, owing to its much lower cost, the latter being due in turn to the fact that toluene-p-sulphonyl chloride is a by-product in the commercial preparation of saccharin. Toluene-p sulphonyl chloride is a crystalline substance, of m.p. 68° the finely powdered chloride will, however, usually react readily with amines in the Schotten-Baumann reaction it does not react so readily with alcohols, but the reaction may be promoted considerably by first dissolving the chloride in some inert water-soluble solvent such as acetone. 

Method 2. Place a 3 0 g. sample of the mixture of amines in a flask, add 6g. (4-5 ml.) of benzenesulphonyl chloride (or 6 g. of p-toluenesulphonyl chloride) and 100 ml. of a 5 per cent, solution of sodium hydroxide. Stopper the flask and shake vigorously until the odour of the acid chloride has disappeared open the flask occasionally to release the pressure developed by the heat of the reaction. AUow the mixture to cool, and dissolve any insoluble material in 60-75 ml. of ether. If a solid insoluble in both the aqueous and ether layer appears at this point (it is probably the sparingly soluble salt of a primary amine, e.g., a long chain compound of the type CjH5(CH2) NHj), add 25 ml. of water and shake if it does not dissolve, filter it off. Separate the ether and aqueous layers. The ether layer will contain the unchanged tertiary amine and the sulphonamide of the secondary amine. Acidify the alkaline aqueous layer with dilute hydrochloric acid, filter off the sulphonamide of the primary amine, and recrystaUise it from dilute alcohol. Extract the ether layer with sufficient 5 per cent, hydrochloric acid to remove all the tertiary amine present. Evaporate the ether to obtain the sulphonamide of the secondary amine recrystaUise it from alcohol or dilute alcohol. FinaUy, render the hydrochloric acid extract alkaline by the addition of dilute sodium hydroxide solution, and isolate the tertiary amine. 

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 ... 

Reflux a mixture of 1 g. (1 ml.) of the amine, 2-3 g. of benzenesulphonyl chloride and 6 ml. of pyridine for 30 minutes. Pour the reaction mixture into 10 ml. of cold water and stir until the product crystallises. Filter off the solid and recrystaUise it from alcohol or dilute alcohol. 

Tile use of benzenesulphonyl chloride or of p-toluenesulphonyl chloride in the separation and identification of amines is described in Section IV,100. 

Method 2. The procedure described under Benzenesulphonyl Chloride, Method 2 (Section IV,206) may be used with suitable adjustment for the difierence in molecular weights between sodium p-toluenesulphonate (Section IV,30) and sodium benzenesulphonate. When the reaction product is poured on to ice, the p-toluenesulphonyl chloride separates as a sohd. This is filtered with suction it may be recrystaUised from hght petroleum (b.p. 40-60°) and then melts at 69°. 

Benzenesulphonyl chloride reacts with primary and secondary, but not with tertiary, amines to yield substituted sulphonamides (for full discussion, see Section IV,100,3). The substituted sulphonamide formed from a primary amine dissolves in the alkaline medium, whilst that produced from a secondary amine is insoluble in alkali tertiary amines do not react. Upon acidifying the solution produced with a primary amine, the substituted sulphonamide is precipitated. The reactions form the basis of the Hinsberg procedure for the separation of amines see Section IV,100,(viii) for details. Feebly basic amines, such as o-nitroaniline, react slowly in the presence of allcali in such cases it is best to carry out the reaction in pyridine solution see Section IV,100,3. ... 

Benzenesulphonyl chloride test. Proceed as in the benzoyl chloride test, but use 15-20 ml. of 5 per cent, sodium hydroxide solution. Examine the product when the odour of the sulphonyl chloride has disappeared. (If no reaction has occurred, the substance is probably a tertiary amine.) If a precipitate appears in the alkaline solution, dilute with about 10 ml. of water and shake if the precipitate does not dissolve, a secondary amine is indicated. If the solution is clear, acidify it cautioiosly to Congo red with dilute hydrochloric acid a precipitate is indicative of a primary amine. 

The order of reaction with respect to aluminium chloride was ill-defined. Since nitrobenzene and aluminium chloride form a 1 1 complex which exhibits the simple monomeric molecular weight in nitrobenzene solution185, and since even in solutions of aluminium chloride and benzoyl chloride in nitrobenzene the aluminium chloride is preferentially associated with the solvent184, then in nitrobenzene solutions of aluminium chloride and benzenesulphonyl chloride the lesser basicity of the latter relative to benzoyl chloride means that the aluminium chloride must be mainly associated with nitrobenzene and in equilibrium with aluminium chloride associated with the sulphonyl chloride184. By analogy with... 

Jensen and Brown184 have also reinvestigated the kinetics of benzenesulphonyl-ation using benzenesulphonyl chloride as solvent. They found that for toluene,... 

In arriving at the mechanism of sulphonylation under these conditions account was taken of the facts that (a) Olivier183 had shown that aluminium chloride and benzenesulphonyl chloride forms a 1 1 complex so that the rate equations (82) and (83) become (84) and (85), respectively, viz. 

Alkylation reactions. In a laboratory procedure for the alkylation of benzene with benzyl chloride using the catalyst EPZIO at room temperature 100% conversion of the alkylating agent in less than 15 minutes was obtained (Envirocats, 1990). EPZE was efficiently used in the sulphonation of o-xylene with benzenesulphonyl chloride to give 3,4-... 

It is generally more convenient to employ the solid p-toluenesulphonyl chloride (m.p. 69°) rather than the liquid benzenesulphonyl chloride. More-ova-, the benzenesulphonamides of certain secondary amines are oils or low melthig point solids that may be difficult to crystallise the p-toluenesulphon-amides usually have higher melting points and are more satisfactory as derivatives. Technical p-toluenesulphonyl chloride may be purified by dissolving it in benzene and precipitating with light petroleum (b.p. 40-60°). 

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