Aromatic compounds benzene sulfonic acid

For many years phenol was made on a large industrial scale from the substitution reaction of benzene sulfonic acid with sodium hydroxide. This produced sodium sulfite as a by-product. Production and disposal of this material, contaminated with aromatic compounds, on a large scale contributed to the poor economics of the process, which has now been replaced by the much more atom economic cumene route (see Chapter 2, Schemes 2.2 and 2.3). 

In contrast, reversed-phase sorbents have non-polar functional groups, e.g. octadecyl, octyl and methyl, and conversely are more likely to retain non-polar compounds, e.g. polycyclic aromatic hydrocarbons. Ion-exchange sorbents have either cationic or anionic functional groups and when in the ionized form attract compounds of the opposite charge. A cation-exchange phase, such as benzene-sulfonic acid, will extract analytes with positive charges (e.g. phenoxyacid herbicides) and vice versa. A summary of the commercially available silica-bonded sorbents is given in Table 8.1. 

Aromatic derivatives are known, including benzene sulfonic acid (81 see Chapter 21). Sulfonic acid 82 is a generic sulfonic acid derived from an aromatic compound (Ar = aryl), where an aryl group is any benzene derivative. The aryl group may also be a polynuclear aromatic compound (see Chapter 21, Section 21.8). The nomenclature for 78 and aryl derivatives is presented in Chapter 21. 

A mixture of ester is obtained, and the ratio of monoester to diester is controlled by ratios of the compounds charged to the reactor. Excess polyoxyethylene is used to maximize monoester production (5), and excess fatty acid is used to maximize diester formation (6). Because of the existing equilibrium, it is important that water be removed with an azeotroping agent such as toluene, xylene, etc., and/or by use of an inert-gas sparge to carry off water as it is formed to force the equilibrium toward the desired product. Catalysts such as sulfuric acid (7), benzene sulfonic acid, and other aromatic sulfonic acids (5, 8, 9), as well as cationic ion-exchange resins such as polystyrene-sulfonic acids (5, 9), are used. The latter compounds have the advantage of easy removal from batch reactions and of use in a fixed bed for continuous processes. Metals such as tin, iron, and zinc, as well as their salts in powdered form, have been used as catalysts (10,11). Catalysts can improve the yield of monoester. Of course, use of a monohydroxyl-functional polyoxyethylene, such as that from methanol-started ethylene oxide polymers (methoxy-polyoxyethylene), can be esterified with fatty acids to yield effectively all monoester. 

Sulfonic acids can come from the sulfonation of oil cuts from white oil production by sulfuric acid treatment. Sodium salts of alkylaromatic sulfonic acids are compounds whose aliphatic chains contain around 20 carbon atoms. The aromatic ring compounds are mixtures of benzene and naphthalene rings. 

Nitrations can be performed in homogeneous media, using tetramethylene sulfone or nitromethane (nitroethane) as solvent. A large variety of aromatic compounds have been nitrated with nitronium salts in excellent yields in nonaqueous media. Sensitive compounds, otherwise easily hydroly2ed or oxidized by nitric acid, can be nitrated without secondary effects. Nitration of aromatic compounds is considered an irreversible reaction. However, the reversibihty of the reaction has been demonstrated in some cases, eg, 9-nitroanthracene, as well as pentamethylnitrobenzene transnitrate benzene, toluene, and mesitylene in the presence of superacids (158) (see Nitration). 

Tnfluoroacetic anhydnde in a mixture with sulfuric acid is an efficient reagent for the sulfonylation of aromatic compounds [44] The reaction of benzene with this system in nitromethane at room temperature gives diphenyl sulfone in 61% yield Alkyl and alkoxy benzenes under similar conditions form the corresponding diaryl sulfones in almost quantitative yield, whereas yields of sulfones from deactivated arenes such as chlorobenzene are substantially lower [44] The same reagent (tnfluoroacetic anhydride-sulfunc acid) reacts with adamantane and its derivatives with formation of isomeric adamantanols, adamantanones, and cyclic sultones [45]... 

Sulfonation (Section 12.4) Sulfonic acids are formed when aromatic compounds are treated with sources of sulfur trioxide. These sources can be concentrated sulfuric acid (for very reactive arenes) or solutions of sulfur trioxide in sulfuric acid (for benzene and arenes less reactive than benzene). 

Okamoto and co-workers noted that N-phenylhydroxylamine gave predominately diphenylamine on treatment with benzene in TFA but mostly 4-aminobiphenyl and 2-aminobiphenyl in the stronger acid trifluoromethane-sulfonic acid (TFSA). Similar results were obtained if benzene was replaced by toluene or anisole. The authors suggested that the reaction in TFA proceeded through O-protonated hydroxylamine either via a direct Sn2 displacement on N by the aromatic nucleophile or via attack of the aromatic compound on the N of a nitrenium ion. In TFSA they favored a mechanism in which the diprotonated hydroxylamine lost water to generate an iminium-benzenium dication (11, Scheme 5), a protonated nitrenium ion. " This... 

There have been a number of reports of improved selectivity with sulfonic acid resin catalysts compared with conventional liquid acid catalysts[6—9]. Various explanations have also been proposed. If mechanisms usually postulated for condensation reactions with liquid Br0nsted acid [10] and solid acid catalysts [11] are adopted, the sequence of steps shown in Fig. 2 could be considered for the condensation of MFC. Both mechanisms incorporate the essential features of known carbenium ion chemistry, i.t., electrophilic attack on the aromatic ring by polar carbenium ion intermediates. Note that MDU is formed by this attack on the benzene ring of MPC, while the N—benzyl compound by the attack on nitrogen atom. 

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. 

The conventional resinsulfonic acids such as sulfonated polystyrenes (Dowex-50, Amberlite IR-112, and Permutit Q) are of moderate acidity with limited thermal stability. Therefore, they can be used only to catalyze alkylation of relatively reactive aromatic compounds (like phenol) with alkenes, alcohols, and alkyl halides. Nafion-H, however, has been found to be a suitable superacid catalyst in the 110-190°C temperature range to alkylate benzene with ethylene (vide infra) 16 Furthermore, various solid acid catalysts (ZSM-5, zeolite /3, MCM-22) are applied in industrial ethylbenzene technologies in the vapor phase.177... 

In addition to the ozonolysis of alkenes and a few aromatic compounds [93, 104], ozone oxidizes other groups. Thus saturated hydrocarbons containing tertiary hydrogen atoms are converted into tertiary alcohols [105, 106], and some alkenes are transformed into epoxides [107] or a,p-unsat-urated ketones [108], Benzene rings are oxidized to carboxylic groups [109, ethers [110] and aldehyde acetals [111] to esters aldehydes to peroxy acids [772] sulfides to sulfoxides and sulfones [775] phosphines and phosphites to phosphine oxides and phosphates, respectively [775] and organomer-cury compounds to ketones or carboxylic acids [114]. 

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