4-Nitrochlorobenzene-2-sulfonic

The sodium 2-nitrochlorobenzene-4-sulfonate can be obtained in a pure state by recrystallizing from hot water, dilute salt solution, or aqueous alcohol. 

Nitrochlorobenzene-4-sulfonic acid can be prepared ako by sulfonation of o-nitrochlorobenzene (see Table III).This method,however,is inherently more costly and less reliable than the one given above (nitration of chlorobenzene-4-sulfonic acid), because it requires the isolation of o-nifrochlorobenzene and its separation from the para isomer. Nevertheless, the second method may be preferable technically under those circumstances where the demand for p-nitrochlorobenzene is so large that a use for the by-product ortho isomer is need. At the present time, the situation is reversed. The manufacture of o-nitroanisole uses so much o-nitrochloroben-zene that the accumulated para compound is partly used in making p-nitroaniline. 

Reduction of 2-nitrochIorobenzene-4-sulfonic acid gives o-chlorometanilic acid which is used in making azo dyes. The real technical value of nitrochlorobenzene-sulfonic acid, however, lies in the ability of its chlorine atom to be replaced by various groups. For example, o-nitrophenol-p-sulfonic acid is obtained by treatment wiui sodium hydroxide, and this product, on reduction, yields o-aminophenol-p-sulfonic acid. An ogously, nitrochlorobenzenesulfonic acid gives o-nitroanisole-p-sulfonic acid by treatment with alcoholic methanol, and from this is obtained o-anisidine-p-sulfonic acid. The action of ammonia on nitrochlorobenzenesulfonic acid produces o-nitroaniline-p>sulfonic acid aniline and its derivatives produce o-nitrodiphenylamine-p Sulfonic acids (cf. Table II). 

In 1988, the United States consumption of monochlorobenzene was 120 million kilograms 42% for the production of nitrochlorobenzenes, 28% for solvent uses, and the remaining 30% for other appHcations such as diphenyl ether, ortho- and i ra-phenylphenols, sulfone polymers, and diphenyldichlorosilane, an intermediate for specialty siHcones. 

Replacing the sulfonic acid 27 with the appropriate carboxy-, carboxamido-, sulfonyl-, or sulfon-amido-4-nitrochlorobenzene leads to analogues described in [61], [62],... 

Analogous Sulfonations. Exactly the same method can be used for sulfonating p-nitrochlorobenzene, p-nitrotoluene, o-m trochlorobenzene, chlorobenzene, and many other compounds. On the other hand, it is usually not possible to sulfonate dinitaro compounds in this way. Dinitrochlorobenzene and dinitrotoluene are decomposed explosively by treatment with fuming sulfuric acid. If dinitrochloro-benzenesulfoitic acid is to be prepared, for example, one starts with p-nitrochloro-benzene/ This is sulfonated, as described previously, and the sulfonic acid is converted to dinitrochlorobenzenesulfonic acid by treatment with mixed acid (50 50 sulfuric and nitric acids) at low temperatures. This product yields, on replacement of the chlorine by —OH and partial reduction, 4-nitro-2-aminophenol-6-sulfonic acid (nitro acid III), which is used in preparing chrome dyes. 

Nitrobenzene, the nitrotoluenes, and nitrochlorobenzenes can be sulfonated with oleum at moderate temperatures, but violent explosions have occurred during these sulfonations. Dinitrobenzenesulfonic acids are prepared by nitration of the mononitro sulfonates since dinitro compounds decompose when sulfonated. 

A variety of isomeric or closely related mixtures of organic compounds are often found when manufacturing chemical and pharmaceutical products. However, it is usually necessary to separate these molecules in order to obtain the expected functionality of the products. Conventional methods such as distillation, extraction and crystallization might be difficult to use since the molecules to be separated might have very close chemical and physical properties. Hydrotropes are known to be selective in the solubilization of compounds and as mentioned earlier, do not perform so generally as surfactants. It has been found that the solubility enhancement in water by adding the hydrotrope sodium xylene sulfonate (SXS) will vary for different isomers such as o- and /7-nitrochlorobenzene, as well as for o- and p-dichlorobenzene (24). In this case, the c -isomer is more soluble than the p-isomer. Higher solubilities have also been reported for aromatic compounds when compared to aliphatic and alicyclic compounds (24). This selective... 

Monochlorobenzene. The largest use for monochlorobenzene, accounting for about 40 percent of the consumption, is in the production of chloronitrobenzenes. p-Nitro-chlorobenzene (NCR) is converted into p-phenylenediamines for use as antioxidants in rubber processing. A smaller use for NCR is in the synthesis the pain reliever acetaminophen. ort/io-Nitrochlorobenzene is a raw material for producing insecticides and several azo pigments. A large number of dyes also can be derived from either chlorobenzene or nitro-chlorobenzene. About 25 percent of the monochlorobenzene is used as a solvent for pesticide formulation and in MDI processing. The manufacture of diphenyl oxide, for heat transfer fluids, and phenylphenols, for disinfectants, consumes another 22 percent. About 8 percent is used to make dichloro-diphenylsulfone, an intermediate in the manufacture of sulfone polymers. 

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