Replacement sulfonic acid groups

Bromine can replace sulfonic acid groups on aromatic rings that also contain activating groups. PhenoHc sulfonic acids, for example, are polybrominated (24). 

Structure design came from the proton exchange membrane counterparts by replacing sulfonic acid groups with quaternary ammonium or other cationic groups. 

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. 

Azolesulfonic acids frequently exist as zwitterions. The usual derivatives are formed, e.g. pyrazole-3-, -4- and -5-sulfonic acids all give sulfonyl chlorides with PCI5. The sulfonic acid group can be replaced by nucleophiles under more or less vigorous conditions, e.g. by hydroxyl in imidazole-4-sulfonic acids at 170 °C, and by hydroxyl or amino in thiazole-2-sulfonic acids. 

Pyridinesulfonic acids exist as zwitterions e.g. 874). As for benzenesulfonic acid, the sulfonic acid group can be replaced by hydroxy or cyano groups under vigorous conditions, e.g. (874) — (873), (875). 

This nucleophilic replacement of halogen atoms proceeds under mild conditions due to the neighboring azo group and the presence of copper ions. The o-sulfonic acid group is also susceptible to the copper-mediated nucleophilic substitution, and other nucleophiles, such as alkoxy, alkylamino, cyano, and sulfinic acid can also replace the halogen atom in the position ortho to the azo group in the presence of copper ions. 

Other similar fiber-reactive triphenodioxazines are prepared by replacing the sulfonic acid group in 26 with a 2-hydroxyethylsulfonyl group. The starting material here is 4-chloro-3-(2-hydroxyethylsulfonyl) nitrobenzene (35), which leads to products containing a VS group bound directly to the dioxazine ring (36) [64,66] (Scheme 3.3). 

Replacement of a hydrogen atom by a sulfonic acid group, —SO3H. (p. 761)... 

Fig. 13.144 (1) sulfonation, (2) chromate oxidation to give the naphthalic anhydride (64), (3) condensation with A-methylamine, and (4) replacement of the sulfonic acid group in a reaction with methoxide. This process gives C.I. Fluorescent Brightener 162. 

The initial high conductivity is attributable to the protons from the highly dissociated sulfonic acid groups. As alkali is added, the conductivity drops linearly as H+ is replaced by the less conducting Na+ ion. The horizontal portion of the curve corresponds to the titration of weaker carboxylic acid... 

Aminoanthraquinone affords an example of the replacement of a sulfonic acid group by amino. More recently, however, it has been found better to prepare 2-aminoanthraquinone from 2-chloroanthra-quinone, since this leads to a purer product, o- and p-Nitroanilines are prepared today almost exclusively from the corresponding nitrochloro-benzenes (page 92). 

Replacement of the Sulfonic Acid Group by the Hydroxyl Group. 167... 

The replacement of the sulfonic acid group by halogen is governed largely oy groups already present on the nucleus. When there is no other group, as in benzenesulfonic acid, the replacement does not take place. The reaction occurs readily with phenolic sulfonic acids and is... 

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