Replacement of sulfonic acid groups

Desulfonation s. a. Replacement of sulfonic acid groups by hydrogen N-Desulfonation, oxidative... 

Activation of substitution reactions by N-oxide groups Replacement of sulfonic acid groups by hydroxyl partial s. 17, 559 Phenols from ar. sulfonic acids s. 19,279... 

The breakthrough in membrane development and the precondition for the membrane process as an alternative for the amalgam process was in 1975 the replacement of sulfonic acid groups by carboxylic acid groups in a perfluorinated membrane polymer, initially applied by the Asahi Glass Company [1,2]. 

Replacement of Sulfonic Acid Ester Groups by Fluoride... 

Replacement of sulfonic acid chloride groups by hydrogen... 

Among the indirect methods of preparing aromatic nitro compounds are the displacement of sulfonic acid groups with nitro groups and the replacement of diazonium groups. 

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... 

Sulfonation Treatment of benzene with hot concentrated sulfuric acid gives benzenesulfonic acid A sulfonic acid group (—SO2OH) replaces one of the ring hydrogens... 

Anthraquinone can be sulfonated, nitrated, or halogenated. Sulfonation is of the greatest technical importance because the sulfonic acid group can be readily replaced by an amino or chloro group. Sulfonation with 20—25% oleum at a temperature of 130—135°C produces predominandy anthraquinone-2-sulfonic acid [84-48-0]. By the use of a stronger oleum, disulfonic acids are produced. The second sulfonic acid substituent never enters the same ring a mixture of 2,6- and 2,7-disulfonic acids is formed (Wayne-Armstrong rule). In order to sulfonate in the 1-, 1,5-, or 1,8-positions, mercury or one of its salts must be used as a catalyst. 

Pyrazolesulfonic acids, like (493), have high melting points (Table 24) and probably exist as the zwitterions (497). They are very stable to hydrolysis and only afford pyrazolones at high temperatures. The replacement of the SO3H group by bromine has also been reported (B-76MI40402). Pyrazole-3-, -4- and -5-sulfonic acids react with phosphorus pentachloride to form sulfonyl chlorides. 

The subsequent reaction of the pure 1-nitroanthraquinone to 1-aminoan-thraquinone used to be carried out mainly by reaction with sodium sulfides in an alkaline medium and is now performed by nucleophilic replacement of the nitro group with ammonia in organic solvents, affording up to 98% yield. The overall reaction affords approximately 70% yield, in comparison to the roughly 50% yielded by the classical method which proceeds via the 1-sulfonic acid. Moreover, the newer method is also superior to the old one because recyclization of the solvent makes it ecologically more attractive. 

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