Chlorosulphonic acid

C7H7CIO1S, p-CHjCjsH SOjCI. Colourless crystals, m.p. 7l°C, formed by the action of chlorosulphonic acid on toluene. Esters of toluenesulphonic acid are frequently called tosylatesand their formation tosylation. Many tosylates are easily obtained crystalline, and the reaction is thus of considerable importance. 

A further difference between aliphatic and aromatic hydrocarbons is that only the latter are capable of direct sulphonation. Thus benzene when heated with concentrated sulphuric acid gives benzenesulphonic acid, a reaction which proceeds more readily, however, if chlorosulphonic acid is used instead of sulphuric acid an excess of chlorosulphonic acid however may convert the sul phonic acid into the sulphonyl chloride (c/. p. 181). 

Sulphanilamide, the simplest member of a large series of bacteriostatic drugs, can readily be prepared by the following reactions. Acetanilide, when treated v ith an excess of chlorosulphonic acid, gives p-acetaniidobenzencsulphonyl chloride (Reaction A), w hich readily reacts with ammonia to give p-acetamido-benzenesulphonamide (Reaction H). The acetamido-group in the latter... 

The chlorosulphonic acid should he handled ucith great care, and always in a fumcTCUpboard. The technical acid is usually pure enough for the above preparation. If it is dark in colour, it can be further purified by care/yJ distilla- tion (preferably in an all-glass apparatus) and the fraction of b.p. 149-152" collected for use. 

Alkyl sulphates. The dimethyl and diethyl esters may be prepared infer alia by the interaction of chlorosulphonic acid with the anhydrous alcohol, followed by distillation of the resulting alkyl sulphuric acid under diminished pressure, for example ... 

Reaction with chlorosulphonic acid ( chlorosulphonyl-ation ). Sulphonamides. Many aryl hahdes, either alone or in chloroform solution, when treated with excess of chlorosulphonic acid afford the corresponding sulphonyl chlorides in good yield (compare Section IV.106) the latter may be readily converted into the aryl sulphonamides by reaction with concentrated ammonia solution or with sohd ammonium carbonate. 

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. 

The procedure is not usually applicable to aminosulphonic acids owing to the interaction between the amino group and the phosphorus pentachloride. If, however, the chlorosulphonic acid is prepared by diazotisation and treatment with a solution of cuprous chloride in hydrochloric acid, the crystalline chlorosulphonamide and chlorosulphonanilide may be obtained in the usual way. With some compounds, the amino group may be protected by acetylation. Sulphonic acids derived from a phenol or naphthol cannot be converted into the sulphonyl chlorides by the phosphorus pentachloride method. 

Sulphonamides of aryl ethers. Aromatic ethers react smoothly in chloroform solution with chlorosulphonic acid at 0° to give suljihonyl chlorides, for example ... 

A 60 per cent, excess of chlorosulphonic acid is used a smaller excess loads to increased formation of diphenylsulphone (CgH SOjC Hg) at the expense of the Bulphonj l chloride. 

Method 1. In a 750 ml. three-necked flask or wide-mouthed glass bottle, equipped with a dropping funnel, a mechanical stirrer (Fig.//, 7,10) a thermometer (with bulb within 2 cm. of the bottom) and an outlet tube leading to a gas absorption device (Fig. II, 8, 1, c), place 400 g. (228 ml.) of chlorosulphonic acid and cool to 0° in a freezing mixture of ice and... 

The reaction may be more easily controlled and the chlorosulphonic acid added all at once if the acetanilide is employed in the form of a hard cake. The latter is prepared by melting the acetanilide in the flask over a free flame and causing the compound to solidify over the lower part of the flask by swirling the liquid. If the reaction becomes too vigorous under these conditions, cool the flask momentarily by immersion in an ice bath. 

The chemical resistance of PCTFE is good but not as good as that of PTFE. Under certain circumstances substances such as chlorosulphonic acid, molten caustic alkalis and molten alkali metal will adversely affect the material. Alcohols, acids, phenols and aliphatic hydrocarbons have little effect but certain aromatic hydrocarbons, esters, halogenated hydrocarbons and ethers may cause swelling at elevated temperatures. 

The principal applications of these plastics arose from their very good chemical resistance, as they are resistant to mineral acids, strong alkalis and most common solvents. They were, however, not recommended for use in conjunction with oxidising acids such as fuming nitric acid, fuming sulphuric acid or chlorosulphonic acid, with fluorine or with some chlorinated solvents, particularly at elevated temperatures. 

Acetic acid Acetic anhydride Acid mixtures Battery fluids Chloroacetic acid Chlorosulphonic acid Chromic acid Dichloroacetic acid Fluoroboric acid Fluorosilicic acid... 

Charcoal screenings, wet Charcoal, wet Chlorine azide Chlorine dioxide Chloroacetaldehyde Chloroacetone (unstabilized) Chloroacetonitrile Chloroformates, n.o.s. Chloroprene, uninhibited Chlorosulphonic acid Coal briquettes, hot Coke, hot Copper acetylide... 

Chloropropionitrile, 41 o-Chlorostyrene, 41 Chlorosulphonic acid, 41 Chlorothalonil, 41 o-Chlorotoluene, 41 Chloroxuron, 41... 

We can recycle some by-products in a simple way. For example, when chlorosulphonic acid is used for sulphonation/sulphation, HCl gas leaves as a product the disposal of which may be a problem. Here, the dry gas can be reacted with SO3 to give chlorosulphonic acid, which can be recycled. We are, through this methodology, also able to take care of organic materials leaving with the HCl gas. Likewise, when SO2CI2 is used for chlorination, SO2 can be recycled via reaction with CI2. 

Chlorosulphonic acid gave rise to a bad accident, which was interpreted as the result of a huge and violent hydrolysis. 500 kg of 98% sulphuric acid were incorporated into 520 kg of chlorosulphonic acid without stirring the medium. Two liquid layers were formed, which were mixed vigorously when the stirrer started to work. The highly violent release of hydrogen chloride was explained by the action of the hydrolysis of chlorosulphonic acid by the 2% of water contained in the suiphuric acid. 

When it is heated with red phosphorus, suiphuryl chloride gives rise to a very violent reaction. Similar behaviour between phosphorus and chlorosulphonic acid was observed. Above 25-30°C there is an energetic reaction, which speeds up before detonating violently. 

Finally, a particularly dangerous reaction between chlorosulphonic acid and silver nitrate was also observed. This is probably due to the following reaction, which leads to a particularly unstable acid ... 

Chlorosulphonic acid reacts very violently with diphenyl ether if the medium reaches a temperature greater than 40°C. The reaction is the following ... 

The same type of accident was also described as an effect of chlorosulphonic acid on o-nitrophenol ... 

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