Preparation of Sulfonic Acids

Note Great caution should be exercised in handling fuming sulfuric acid and, in general, ali hot sulfonating mixtures. Goggles shovid be worn. 

For semimicro work section (A) or (C) is recommended. For macro work, beside the preparation of sulfanilic acid (section B), sections (C) and (D) may be adapted by increasing the quantities given 4-5 times and using a 250-ml flask. 

Introduction. It will be recalled that one of the most common methods of distinguishing between aromatic and aliphatic hydrocarbons is the difference in the rates of their reactions with sulfuric acid. Aromatic hydrocarbons readily form sulfonic acids when heated with concentrated sulfuric acid at temperatures varying from 80 to 200 . Saturated paraffin hydrocarbons, on the other hand, do not react with sulfuric acid under comparable conditions. A number of saturated paraffins are sulfonated directly by using fuming sulfuric acid and heating under pressure, but the sulfonic acids of the lower paraffin hydrocarbons are prepared by reacting alkyl halides with alkali sulfites. The sulfonic acids of the aromatic hydrocarbons are of much greater importance than the sulfonic acids of paraffins. 

The general method for the preparation of a monosulfonic acid is to heat the aromatic compound with excess of concentrated sulfuric acid at temperatures which vary from 80-200 or even higher. The completion of the reaction is indicated by complete solubility of a small sample diluted with water. During sulfonation water is formed and consequently there is a dilution of the sulfonating medium  

For this reason an excess of 30-40 per cent or more than the calculated amount of sulfuric acid is used. Increase in the rate of sulfonation is obtained by the addition of sulfur trioxide to sulfuric acid. Ordinary concentrated sulfuric acid contains about 96-98 per cent H2SO4, the rest of the liquid being water. Sufficient sulfur trioxide can be added to convert this water to sulfuric acid and thus obtain 100 per cent acid. Addition of still more sulfur trioxide 

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This ch ter contains reactions which prepare the oxides of nitrogen, sulfur and selenium. Included are W-oxides, nitroso and nitro compounds, nitrile oxides, sulfoxides, selenoxides and sulfones. Oximes are considered to be amines and appear in those sections. Preparation of sulfonic acid derivatives are found in Chapter Two and the preparation of sulfonates in Chapter Ten. 

Scheme 2.5 Preparation of sulfonic-acid functionalised ionic liquids...

The procedure described above involves sulfonation in the absence of free sulfuric acid at low temperatures, and avoids the use of an appreciable excess of the sulfonating agent. Similar procedures are generally applicable to the preparation of sulfonic acids which cannot be prepared satisfactorily by the ordinary sul-fonation methods, because they are easily isomerized or sulfonated further by concentrated sulfuric acid. Even compounds which are ordinarily converted directly into disulfonic acids, such as carbazole, 4,4 -dihydroxydiphenylmethane, etc., can be monosulfonated in this way. 

D.J. Connolly and W.F. Gresham, Fluorocarbon vinyl ether polymers. USP 3,282,875, 1966 P.R. Resnick, Preparation of sulfonic acid containing vinyl ethers, USP 3,560,568 K. Kimoto, H. Miyauchi, J. Ohmura, M. Ebisawa and H. Hane, Novel fluorinated copolymers with tridihydro fluorosulfonyl fluoride pendant groups and preparation thereof. USP 4,329,435. 

Use of the various reagents for preparation of sulfonic acids is described in the following Sub-sections the present Sub-section gives only a brief account of the influence of conditions on the course of the reaction. 

Chlorosulfonic acid is not used widely for the preparation of sulfonic acids, partly because excess reagent reacts with the sulfonic acid to form the sulfonyl chloride it is commonly employed for the preparation of sulfonyl chlorides. 

J. Hoyle, Preparation of Sulfonic Acids, Esters, Amides and Halides, in The Chemistry of Sulfonic Acids and their Derivatives, S. Patai and Z. Rappoport (Eds), Wiley, Chichester, 1991, 354, 379. 

It is advantageous to use S-benzylthiuronium chloride for the preparation of sulfonic acid salts, because this type of salt was prepared from numerous sulfonic acids (38—45). 

Preparation of Sulfonic Acid Chlorides and Their Conversion to Amides... 

Alkyl sulfonates are derivatives of sulfonic acids m which the proton of the hydroxyl group is replaced by an alkyl group They are prepared by treating an alcohol with the appropriate sulfonyl chloride usually m the presence of pyridine... 

Keta.Is, Trimethylpentanediol reportedly forms a cycHc ketal by heating it with benzophenone ia the presence of sulfonic acid catalysts at reflux temperatures ia toluene (64). These are said to be useful as aprotic solvents for ink-jet printing and as inflammation inhibitors for cosmetic preparations... 

Sulfonic acid hydrazides, RSO2NHNH2, are prepared by the reaction of hydraziae and sulfonyl haUdes, generally the chloride RSO2CI. Some of these have commercial appHcations as blowiag agents. As is typical of hydrazides generally, these compounds react with nitrous acid to form azides (26), which decompose thermally to the very reactive, electron-deficient nitrenes (27). The chemistry of sulfonic acid hydrazides and their azides has been reviewed (87). 

General Reaction Chemistry of Sulfonic Acids. Sulfonic acids may be used to produce sulfonic acid esters, which are derived from epoxides, olefins, alkynes, aHenes, and ketenes, as shown in Figure 1 (10). Sulfonic acids may be converted to sulfonamides via reaction with an amine in the presence of phosphoms oxychloride [10025-87-3] POCl (H)- Because sulfonic acids are generally not converted directiy to sulfonamides, the reaction most likely involves a sulfonyl chloride intermediate. Phosphoms pentachlotide [10026-13-8] and phosphoms pentabromide [7789-69-7] can be used to convert sulfonic acids to the corresponding sulfonyl haUdes (12,13). The conversion may also be accompHshed by continuous electrolysis of thiols or disulfides in the presence of aqueous HCl [7647-01-0] (14) or by direct sulfonation with chlorosulfuric acid. Sulfonyl fluorides are typically prepared by direct sulfonation with fluorosulfutic acid [7789-21-17, or by reaction of the sulfonic acid or sulfonate with fluorosulfutic acid. Halogenation of sulfonic acids, which avoids production of a sulfonyl haUde, can be achieved under oxidative halogenation conditions (15). 

Other Applications. Hydroxylamine-O-sulfonic acid [2950-43-8] h.2is many applications in the area of organic synthesis. The use of this material for organic transformations has been thoroughly reviewed (125,126). The preparation of the acid involves the reaction of hydroxjlamine [5470-11-1] with oleum in the presence of ammonium sulfate [7783-20-2] (127). The acid has found appHcation in the preparation of hydra2ines from amines, aUphatic amines from activated methylene compounds, aromatic amines from activated aromatic compounds, amides from esters, and oximes. It is also an important reagent in reductive deamination and specialty nitrile production. 

Although the preparation of /3-mercaptoethanesulfonicacid through the ammonolysis reaction is the preferred method, it is also possible to prepare the sulfonic acid by the sodium hydroxide hydrolysis of /3-S-thiuronium ethanesulfonate followed by the ion exchange treatment. The resulting acid, however, is generally not as satisfactory as that prepared by the am-monolysis reaction. 

Imidazolides of aromatic sulfonic acids react much more slowly in alcoholysis reactions than the carboxylic acid imidazolides. Although the reaction with phenols is quantitative when a melt is heated to 100 °C for several hours, with alcohols under these conditions only very slight alcoholysis is observed. In the presence of 0.05 equivalents (catalytic amount) of sodium ethoxide, imidazole sodium, of NaNH2, however, imidazolides of sulfonic acids react with alcohols almost quantitatively and exothermically at room temperature in a very short time to form sulfonic acid esters (sulfonates). (If the ratio of sulfonic acid imidazolide to alcoholate is 1 2, ethers are formed see Chapter 17). The mechanism of catalysis by base corresponds to that operative in the synthesis of carboxylic esters by the imidazolide method. Because of the more pronounced nucleophilic character of alkoxide ions, sulfonates can also be prepared in good yield by alcoholysis of their imidazolides in the presence of hydroxide ions i.e., with alcoholic sodium hydroxide. 45 Examples of syntheses of sulfonates are presented below. 

Tibric acid (10), interestingly, has the m-carboxysulfonamido functionality but its activity is expressed, instead, as suppression of serum triglyceride levels. In its reported preparation, chloro-sulfonic acid treatment converts 2-chlorobenzoic acid to chlorosulfonate 9, which readily forms the hypolipidemic agent tibric acid (10) on reaction with... 

Ligand-free catalysts have been prepared from the following types of nickel(II) compounds nickel salts of long-chain aliphatic or aromatic carboxylic acids (10, 11) or of sulfonic acids (11), nickel enolates of /3-diketones (11) [e.g., nickel acetylacetonate (4, 12)] or their imino derivatives (11, 13), nickel phenolates (11), dithiocarbamates (14), and mer-captides (15). 

A. Cahn, H. Lemaire, R. Haass, Preparation of sulfonated fatty acid ester surface-active agents, US Patent 3 320 292 (1967). 

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