Benzenesulfonic acid preparation

Sodium Benzenesulfonate. Benzenesulfonic acid prepared continuously in a cascade series of six 2,000-gal cast-iron vessels is fed to a neutralizer system. Sodium sulfite slurry from reaction (3) is fed into the neutraliza tion tank at a constant rate while the benzenesulfonic acid flow is regulated to keep the reaction mixture distinctly acid. Sulfur dioxide is liberated [Eq. (2)] and piped for acidification of sodium phenoxide [Eq. (4)], and some is sent to another plant for purification and liquefaction. 

Sulfonation. Benzene is converted iato benzenesulfonic acid [98-11-3] C H SO, upon reaction with fuming sulfuric acid (oleum) or chlorosulfonic acid. y -Benzenedisulfonic acid [98-48-6] CgHgS20, is prepared by reaction of benzene-sulfonic acid with oleum for 8 h at 85°C. Often under these conditions, appreciable quantities ofT -benzenedisulfonic acid [31375-02-7] are produced. 1,3,5-Benzenetrisulfonic acid [617-99-2] C H S Og, is produced by heating the disulfonic acid with oleum at 230°C (21). 

In laboratory preparations, sulfuric acid and hydrochloric acid have classically been used as esterification catalysts. However, formation of alkyl chlorides or dehydration, isomerization, or polymerization side reactions may result. Sulfonic acids, such as benzenesulfonic acid, toluenesulfonic acid, or methanesulfonic acid, are widely used in plant operations because of their less corrosive nature. Phosphoric acid is sometimes employed, but it leads to rather slow reactions. Soluble or supported metal salts minimize side reactions but usually require higher temperatures than strong acids. 

Reaction of benzenesulfonic acid with sodium hydroxide This is the oldest method for the preparation of phenol. Benzene is sulfonated and the benzenesulfonic acid heated with molten sodium hydroxide. Acidification of the reaction mixture gives phenol. 

Problem 19.28 Prepare (a) 2-bromo-4-hydroxytoluene from toluene, (b) 2-hydroxy-5-methylbenzaIdehyde from p-toluidine, (c) m-methoxyaniline from benzenesulfonic acid. M... 

The benzylideneanilines of Table IX are prepared by refluxing a mixture of 0.010 mole each of the appropriate para-substituted benzaldehyde and aniline in 150 ml of benzene containing 0.1 gm of benzenesulfonic acid for 2-4 hr. A Dean-Stark trap is used to collect the water and then the solvent is removed under reduced pressure. The residue is recrystallized from hexane or other... 

Methoxy is an ortho, para-directing substituent. All that is required to prepare p-methoxy-benzenesulfonic acid is to sulfonate anisole. 

In general, the sulfonic acids are water soluble and are strong acids because of virtually complete loss of ionizable H+ in aqueous solution. They have some important commercial applications, such as in the hydrolysis of fats and oils (see Section 3.5) to fatty acids and glycerol. Benzenesulfonic acid is fused with NaOH in the preparation of phenol. Dyes and some pharmaceutical compounds are manufactured from p-toluenesulfonic acid. Methanesulfonic acid has been developed as an esterification catalyst in place of sulfuric acid for the synthesis of resins in paints and coatings. 

Furfural (18) was oxidized to give the butenolide 19, which on Michael condensation with diethyl ethylmalonate afforded lactone 20. Hydrolysis of 20 yielded the dilactone 21. This was treated with ethanol in the presence of sulfuric acid. The isomer mixture obtained was separated by preparative thin-layer chromatography, yielding 4-ethoxy-3-ethoxycarbonylmethyl-2-ethyl-4-butanolide (22). Elimination of ethanol, with the aid of p-amino-benzenesulfonic acid, gave 2-(3//)-furanone 23 the 2-(5//)-furanone isomer 24 was obtained with the aid of orthophosphoric acid. Both isomeric esters gave the acid 25 after hydrolysis, which on catalytic hydrogenation afforded m-3-carboxymethyl-2-ethyl-4-butanolide 26, identical to homopilopic acid. This synthesis of homopilopic acid differs from earlier syntheses because the less stable cw-2,3-disubstituted butanolide (26) is formed in the last step. 

Remarks. Ferrous sulfate can be used advantageously instead of salt to precipitate the m-nitrobenzenesulfonic acid. The iron salt is very difficultly soluble in 20 per cent sulfuric acid and can be filtered off directly without further treatment. The reduction is carried out exactly as described above. If benzene is sulfonated with 100 per cent sulfuric acid, and then the benzenesulfonic acid is nitrated at 100°, there are formed, according to the work of Obermiller, besides the meta sulfonic acid, considerable quantities of the ortho and para isomers. The latter can be separated quite easily tluough the magnesium salts, and this affords a method for obtaining the valuable o-aminobenzenesulfonic acid. The preparation of orthanilic acid starting with o-m trochlorobenzene has also been described. ... 

Benzenesulfonic acids arc prepared by direct suifonation of aromatic hydrocarbons. 

It then appears analogous to benzenesulfonic acid (as methylcarbonic acid). The remarkable preparation of propionic acid by action of carbon dioxide on cthylsodium, which has very recently been discovered by WanMyn, can then be understood in the same way as the formation of benzenesulfonic acid from benzene and sulfuric acid anhydride. 

Small amounts of butadiene can be prepared conveniently as follows from 1,3-butanediol, a starting material supplied by Aldrich and by Eastman a mixture of 45 g. of the diol, 200 g. of phthalic anhydride, and 5 g. of benzenesulfonic acid on distillation for 2 hrs. affords butadiene in 47% yield. 

Mesoporous SBA-15 silica that contains both benzenesulfonic acid and propylamine was prepared by the sol-gel technique from tetraethyl orthosilicate (TEOS, 120), 2-(4-chlorosulfonylphenyl)ethyl-trimethoxysilane (119) and (3-aminopro-pyl)trimethoxysilane (118) in the presence of poly(ethylene glycol)-Z)/ock-poly (propylene glycol)-Z)/ock-poly(ethylene glycol) [P123] (Scheme 3.34). ... 

Benzenesulfonic acids are prepared by direct sulfonation of aromatic hydrocarbons. 

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