This group of compounds comprises methylbenzenesulfonic acids (toluenesulfonic acids), [25231-46-3] , C7H8O3S, Mr 172.20, methylbenzenedisulfonic acids (toluenedisulfonic acids) C7H8O6S2 , Mr 252.26, dimethylbenzenesulfonic acids (xylenesulfonic acids) [58723-02-7] , C8H10O3S, Mr 186.23, and their derivatives.
Production. The sulfonation of toluene is accomplished more easily than that of benzene and is accompanied by less sulfone formation. Low temperatures favor o-substitution; m-substitution occurs only to the extent of about 2 – 3 %. At temperatures around 100 °C the ratio of o- to p-substitution is about 3 : 7. The sulfuric acid concentration has a strong influence on the isomer ratio [4]. Surprisingly, almost 100 % p-substitution is obtained at –10 °C if sulfur dioxide is used as the solvent [5].
At a sulfonation temperature of 100 °C and a sulfuric acid concentration of 97.4 %, 31 % m-substitution is achieved [6]. Through rearrangement at 140 – 200 °C the concentration of m-toluenesulfonic acid rises to about 46 % [7][8]. If this is followed by hydrolysis with steam at 170 – 200 °C, the concentration of m-isomer rises to more than 90 % [9].
Isolation from the Mixture. p-Toluenesulfonic acid can be crystallized from 66 – 71 % sulfuric acid, or from concentrated hydrochloric acid at temperatures below 0 °C [10]. Then, according to the reaction conditions of the preceding sulfonation, the o- or m-toluenesulfonic acid can be obtained from the mother liquor. If the compounds are required to be very pure, the route via the toluidines (diazotization and reaction with sulfur dioxide) is preferred [47].
2,6-Toluenedisulfonic acid can be obtained by adding 65 % oleum to the sulfonation reaction mixture while the temperature is below 100 °C and then raising the temperature to 125 °C. In 90 % sulfuric acid at 190 °C, 64 % of the 2,4-toluenedisulfonic acid rearranges to 3,5-toluenedisulfonic acid. The 3,5-isomer is isolated from hydrochloric acid solution at –15 °C [11].
Uses. Toluenesulfonic acids are used as isomer mixtures, or as mixtures with xylenesulfonic acids; they serve as solubilizers, as acidic catalysts, and as additives for detergents [12]. They are used as intermediates in the production of cresols and sulfobenzoic acids.
2-Methylbenzenesulfonic Acid [88-20-0] , o-toluenesulfonic acid, C7H8O3S, Mr 172.20, flaky crystals (dihydrate), mp 62.1 °C.
Produced together with 4-methylbenzenesulfonic acid by sulfonation of toluene with 96 % sulfuric acid at 40 °C, or preferably with 1 mol of chlorosulfuric acid at 0 to –10 °C. Used to produce o-sulfobenzoic acid.
2-Methylbenzenesulfonyl Chloride [133-59-5] , C7H7ClO2S, Mr 190.65, bp13 mbar 126 °C, mp 15.5 °C. Manufactured by treating toluene with chlorosulfuric acid at temperatures not exceeding 3 °C, forcing the reaction mixture into ice, siphoning off the water, and centrifuging 4-methylbenzenesulfonyl chloride. Used in the production of toluenesulfonamide.
2-Methylbenzenesulfonamide [88-19-7] , C7H9NO2S, Mr 171.22, mp 156.5 °C, is obtained by treating 2-methylbenzenesulfonyl chloride with aqueous ammonia (d 0.910). Purified by fractional precipitation: hydrochloric acid is added to a solution which has been rendered alkaline with sodium hydroxide; the impurities are precipitated first. Used in the manufacture of saccharin (® Sweeteners - 6.4. Saccharin).
3-Methylbenzenesulfonic Acid [617-97-0] , m-toluenesulfonic acid, C7H8O3S, Mr 172.20. The pure acid can be obtained from m-toluidine. Isomer mixtures with m-isomer concentrations of more than 50 % are obtained from toluene sulfonation mixtures by bubbling in toluene vapor at 180 – 205 °C [13] , see also [9]. Used to manufacture m-cresol (® Cresols and Xylenols).
3-Methylbenzenesulfonyl Chloride [1899-93-0] , C7H7ClO2S, Mr 190.65, bp29 mbar 146 °C, mp 11.7 °C. Obtained from m-toluidine according to [33]. Yield: 71.2 %.
3-Methylbenzenesulfonamide [1899-94-1] , C7H9NO2S, Mr 171.22, mp 103 °C.
4-Methylbenzenesulfonic Acid [104-15-4] , p-toluenesulfonic acid, C7H8O3S, Mr 172.20, mp 38 °C, monohydrate mp 106 °C, trihydrate mp 93 °C, bp26.3 mbar 140 °C.
Production. According to the process of Allied Chemical and Dye Corp. [14] , boiling toluene is sulfonated with 90 – 95 % sulfuric acid. Evaporating toluene is condensed, separated from water, dried, and recycled. A mixture with a p-isomer content of 75 – 85 %, an o-isomer content of 10 – 20 %, a m-isomer content of 2 – 5 %, and less than 1 % of sulfuric acid is present at the end of the reaction. There is very little sulfone formation. The process can also be performed continuously in a vertical reactor [16].
The reaction of toluene in a continuous process with sulfur trioxide as sulfonating agent allows toluenesulfonic acid to be generated with high para selectivity and with the advantage of few byproducts and low waste-gas emissions [15].
For some purposes, for example, for use as an acidic catalyst or in cresol manufacture, the crude toluenesulfonic acid obtained according to the above processes does not have to be purified. Purification is possible by crystallization from 66 % sulfuric acid or via the barium salt.
Uses. The applications of 4-methylbenzenesulfonic acid include the manufacture of 4-formylbenzenesulfonic acid, p-sulfobenzoic acid, 2-chlorotoluene-4-sulfonic acid, and 4-(chloromethyl)phenylmethanesulfonic acid.
4-Methylbenzenesulfonyl Chloride [98-59-9], tosyl chloride, C7H7ClO2S, Mr 190.65, bp25 mbar 138 – 139 °C, mp 69 °C. Formed as a byproduct in the manufacture of 2-methylbenzenesulfonyl chloride, from which it can be separated by remelting several times under water.
This compound is used in the production of sulfonamides, arylides, nuclear-substituted toluenesulfonyl chlorides, 4-(chloromethyl)benzenesulfonyl chloride, and p-toluenesulfinic acid. The tosylation of hydroxyl groups, i.e., their esterification with p-toluenesulfonyl chloride, serves to protect these groups; this method is employed particularly often in the chemistry of natural substances [17].
4-Methylbenzenesulfonamide [70-55-3], C7H9NO2S, Mr 171.22, mp 137 °C, dihydrate mp 105 °C, weak acid, soluble in aqueous alkali. Produced from the sulfonyl chloride with aqueous ammonia. Used in the production of chloroamines, e.g., chloramine T and dichloramine T (® Chloroamines).
Methyl 4-Methylbenzenesulfonate [80-48-8], C8H10O3S, Mr 186.23, bp17 mbar 168 – 170 °C, mp 28 °C, is obtained from the chloride of the acid by reaction with methanol; important alkylating agent.
Ethyl 4-Methylbenzenesulfonate [80-40-0], C9H12O3S, Mr 200.26, bp0.4 mbar 137 – 139 °C, bp12 mbar 165 – 166 °C, mp 34 °C, is obtained from the sulfonyl chloride and ethyl alcohol at –5 to 0 °C after addition of 45 – 50 % sodium hydroxide solution [18]. Used as an alkylating agent and as a plasticizer.
4-(Chloromethyl)benzenesulfonic Acid [46062-27-5], C7H7ClO3S, Mr 206.65, hygroscopic crystals, is obtained at a yield of 90 % through the action of chlorine on sodium 4-methylbenzenesulfonate in the presence of dichlorobenzene [19]. Used in the manufacture of surfactants.
4-(Chloromethyl)benzenesulfonyl Chloride [2389-73-3], C7H6Cl2O2S, Mr 225.09, mp 64 – 65 °C, bp20 mbar 183 – 195 °C, is obtained by treating 4-methylbenzenesulfonyl chloride with chlorine in the presence of PCl5 at 120 – 140 °C.
Methyl 4-(Chloromethyl)benzenesulfonate [89981-68-0] , C8H9ClO3S, Mr 219.67, is used as a quaternizing agent. Reactions with tertiary amines, e.g., trimethylamine, give sulfobetaines with fungistatic properties [20].
4-(Acetylaminomethyl)benzenesulfonyl Chloride [39169-92-1] , C9H10ClNO3S, Mr 247.70, mp 95 – 97 °C, is obtained from N-acetylbenzylamine and chlorosulfuric acid [21].
4-(Acetylaminomethyl)benzenesulfonamide [2015-14-7] , C9H12N2O3S, Mr 228.27, mp 177 °C (from water or aqueous alcohol), is produced from the sulfonyl chloride with aqueous ammonia at 15 and 70 °C; yield 80 %. It is an important intermediate in the manufacture of 4-(aminomethyl)benzenesulfonamide.
4-Methyl-1,3-benzenedisulfonic Acid [121-04-0] , C7H8O6S2 , Mr 252.26, is a viscous oil. Obtained by additional sulfonation of the o- and p-toluenesulfonic acid mixture with 66 % oleum at 125 °C. Used in the manufacture of 4-formyl-1,3-benzenedisulfonic acid, 4-carboxy-1,3-benzenedisulfonic acid, and 4-methylresorcinol.
4-Methyl-1,3-benzenedisulfonyl Chloride [2767-77-3] , C7H6Cl2O4S2 , Mr 289.16, mp 56 °C, is produced from toluene and chlorosulfuric acid at 120 °C [22]. Addition of phosphorus pentoxide raises the yield [23].
4-Methyl-1,3-benzenedisulfonamide [717-44-2] , C7H10N2O4S2 , Mr 250.30, mp 190 – 191 °C.
2,4-Dimethylbenzenesulfonic Acid [88-61-9] , m-xylenesulfonic acid, C8H10O3S, Mr 186.23, dihydrate: mp 57 °C, prisms or flakes. Produced by sulfonating m-xylene with concentrated sulfuric acid; the acid is precipitated by dilution with water. Of the three isomeric xylenes, m-xylene is the one most easily sulfonated. The ease of sulfonation decreases in the order m>p>o, whereas the ease of hydrolysis increases in the order o
2,4-Dimethylbenzenesulfonyl Chloride [609-60-9] , C8H9ClO2S, Mr 204.68, mp 34 °C.
2,4-Dimethylbenzenesulfonamide [7467-12-1] , C8H11NO2S, Mr 185.25, mp 138 °C.
2,5-Dimethylbenzenesulfonic Acid [609-54-1] , C8H10O3S, Mr 186.23, mp 48 °C, bp 149 °C (cathode vacuum), is soluble in chloroform. The dihydrate, mp 95 °C, is obtained by sulfonating p-xylene with 93 % sulfuric acid and removing the water by distillation [24]. Used in the production of 2,5-xylenol.
2,5-Dimethylbenzenesulfonyl Chloride [19040-62-1] , C8H9ClO2S, Mr 204.68, mp 25.5 °C, bp29 mbar 152 – 153 °C.
2,5-Dimethylbenzenesulfonamide [6292-58-6], C8H11NO2S, Mr 185.25, mp 148 °C.
4-Ethylbenzenesulfonic Acid [98-69-1], C8H10O3S, Mr 186.21, is produced by sulfonating ethylbenzene with sulfuric acid. It is separated from the isomers via the aniline salt [25]. Used in the production of p-ethylphenol.
4-(2-Bromoethyl)benzenesulfonic Acid [54322-31-5] , C8H9BrO3S, Mr 265.13; S-benzylisothiuronium salt, mp 149 – 150 °C. The acid is obtained by sulfonating 1 mol of (bromoethyl)benzene with 1.1 mol of SO3 in methylene chloride [26] , see also [27] , [28]. The potassium salt is obtained by treating the sulfonyl chloride with potassium carbonate in water [29].
4-(2-Bromoethyl)benzenesulfonyl Chloride [64062-91-5] , C8H8BrClO2S, Mr 283.58, is produced from 2-(bromoethyl)benzene and chlorosulfuric acid at temperatures not exceeding 25 °C [30]. Used in the production of 4-vinylbenzenesulfonic acid.
4-(2-Bromoethyl)benzenesulfonamide [5378-84-7] , C8H10BrNO2S, Mr 264.15, mp 185.5 – 186 °C.
4-Vinylbenzenesulfonic Acid [98-70-4] , C8H8O3S, Mr 184.21; p-toluidine salt, mp 182 – 183 °C, is obtained in the form of the potassium salt from 4-(2-bromoethyl)benzenesulfonic acid with methanolic KOH [51] or from 4-(2-bromoethyl)benzenesulfonyl chloride with alcoholic KOH [52]. The monomer can be stabilized by adding 0.5 – 5 % of sodium nitrite [53].
4-Vinylbenzenesulfonic acid has been proposed for copolymerization with acrylonitrile to improve the dyeing properties of the fibers [54] and as a starting product in the manufacture of polymeric styrenesulfonic acid [51] , [52].
4-Vinylbenzenesulfonamide [2633-64-9] , C8H9NO2S, Mr 183.23, mp 138 – 139 °C [55].
4-tert-Butyl-2,6-dimethylbenzenesulfonic Acid [28188-48-9] , C12H18O3S, Mr 242.31, is prepared from 1-tert-butyl-3,5-dimethylbenzene with 5 % oleum at 20 – 45 °C. Used in the manufacture of 4-tert-butyl-2,6-dimethylphenol and 2,6-xylenol [56].
2,3-Dihydro-1H-indene-5-sulfonic acid [40117-41-7] , C9H10O3S, Mr 198.24, is obtained by precipitation as a sodium salt, after 2,3-dihydro-1H-indene and concentrated sulfuric acid have been reacted at 150 °C [57]. At low temperatures mainly 1H-indene-4-sulfonic acid is formed. 1H-Indene-5-sulfonic acid has been proposed as a starting material for the manufacture of sulfonylureas with hypoglycemic effects [58].
2,3-Dihydro-1H-indene-5-sulfonyl Chloride [52205-85-3] , C9H9ClO2S, Mr 216.69, mp 49 °C, bp21 mbar 180 °C, is obtained by treating the sodium salt of 1H-indene-5-sulfonic acid with PCl5 , or by the reaction of 2,3-dihydro-1H-indene and chlorosulfuric acid at 0 – 15 °C, pouring onto ice, and extracting with chloroform [59].
2,3-Dihydro-1H-indene-5-sulfonamide [35203-93-1] , C9H11NO2S, Mr 197.26, mp 135 °C.