Aromatic sulfonic acids, synthesis

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. 

Synthesis of MELS Containing Aromatic Sulfonic Acid Groups... 

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. 

Two substituents on two N atoms increase the number of diaziridine structures as compared with oxaziridines, while some limitations as to the nature of substituents on N and C decrease it. Favored starting materials are formaldehyde, aliphatic aldehydes and ketones, together with ammonia and simple aliphatic amines. Aromatic amines do not react. Suitable aminating agents are chloramine, N-chloroalkylamines, hydroxylamine-O-sulfonic acid and their simple alkyl derivatives, but also oxaziridines unsubstituted at nitrogen. Combination of a carbonyl compound, an amine and an aminating agent leads to the standard procedures of diaziridine synthesis. 

The so-called transdiazotizations are mechanistically related to the introduction of diazonio groups using sulfonic acid azides. An aromatic diazonium ion forms a triazene (diazoamino compound) with an aromatic amine the triazene tautomerizes and dissociates at the Na-Np bond of the original diazonium ion. This reaction is important for the synthesis of the 4-aminobiphenyl-4,-diazonium ion, which cannot be obtained by direct (mono-)diazotization of 4,4 -diaminobiphenyl (Allan and... 

The most common way to modify aromatic polymers for application as a PEM is to employ electrophilic aromatic sulfonation. Aromatic polymers are easily sulfonated using concentrated sulfuric acid, fuming sulfuric acid, chlorosulfonic acid, or sulfur trioxide (or complexs thereof). Postmodification reactions are usually restricted due to their lack of precise control over the degree and location of functionalization, the possibility of side reactions, or degradation of the polymer backbone. Regardless, this area of PEM synthesis has received much attention and may be the source of emerging products such as sulfonated Victrex poly (ether ether ketone). 

Other Applications. Hydroxylainine-O-sulfonic acid has many applications in the area of organic synthesis. The acid has found application in the preparation of hydrazines from amines, aliphatic amines from activated methylene compounds, aromatic amines from activated aromatic compounds, amides from esters, and oximes. 

Sulfonation Substitution of a sulfonic acid group (-SO3H) for a ring hydrogen occurs when benzene reacts with concentrated sulfuric acid and sulfur trioxide. Aromatic-ring sulfonation is a key step in the synthesis of such compounds as aspirin and the sulfa-drug family of antibiotics. 

Sulfonic acids and carboxylic acids can be converted into their acid chlorides by treatment with phosphorus pentachloride or phosphorus oxychloride. Thionyl chloride, SOCl is effective for the synthesis of acyl chlorides, and sulfonyl chlorides can be prepared directly from the aromatic compound by reaction with an excess of chlorosulfonic acid. The acid chlorides are efficient Friedel-Crafts acylating agents, yielding sul-... 

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