Sulfonation, electrophilic aromatic substitution reaction

The hydroxyl group is a strongly activating, ortho- and para-directing substituent in electrophilic aromatic substitution reactions (Section 16.4). As a result, phenols are highly reactive substrates for electrophilic halogenation, nitration, sulfonation, and lTiedel-Crafts reactions. 

Given the reactants, write the structures of the main organic products of the common electrophilic aromatic substitution reactions (halogenation, nitration, sulfonation, alkylation, and acylation). 

The sulfoxidation of benzene (Table 4, entry 38) yields benzenesulfonic acids and the respective derivatives. The electrophilic aromatic substitution reaction gives high yields and aqueous sulfuric acid or oleum is used for the sulfonation reaction, which is performed in cascades of reactor vessels. 

Two of the reactions that are used in the industrial preparation of detergents are electrophilic aromatic substitution reactions. First, a large hydrocarbon group is attached to a benzene ring by a Friedel-Crafts alkylation reaction employing tetrapropene as the source of the carbocation electrophile. The resulting alkylbenzene is then sulfonated by reaction with sulfuric acid. Deprotonation of the sulfonic acid with sodium hydroxide produces the detergent. 

Sulfonation (Section 18.4) An electrophilic aromatic substitution reaction in which benzene reacts with SOsH to give a benzene-sulfonic acid, C6H5SO3H. 

Sulfonation is unusual among electrophilic aromatic substitution reactions in its reversibility. It is also unusual in another way in sulfonation, ordinary hydrogen (protium) is displaced from an aromatic ring about twice as fast as deuterium. These two facts are related to each other and, as we shall see in Sec. 11.16, give us a more detailed picture of sulfonation and of electrophilic aromatic substitution in general. 

The pyridine ring undergoes electrophilic aromatic substitution reactions with great difficulty. Halogenation and sulfonation can be carried out under drastic conditions, but nitration occurs in veiy low yield, and Friedel-Crafts reactions are not successful. Reactions usually give the 3-substituted product. 

Benzene s aromaticity causes it to undergo electrophilic aromatic substitution reactions. The electrophilic addition reactions characteristic of alkenes and dienes would lead to much less stable nonaromatic addition products. The most common electrophilic aromatic substitution reactions are halogenation, nitration, sulfonation, and Friedel-Crafts acylation and alkylation. Once the electrophile is generated, all electrophilic aromatic substitution reactions take place by the same two-step mechanism (1) The aromatic compound reacts with an electrophile, forming a carbocation intermediate and (2) a base pulls off a proton from the carbon that... 

Other typical electrophilic aromatic substitution reactions—nitration (second entry), sulfonation (fourth entry), and Friedel-Crafts alkylation and acylation (fifth and sixth entries)—take place readily and are synthetically useful. Phenols also undergo electrophilic substitution reactions that are limited to only the most active aromatic compounds these include nitrosation (third entry) and coupling with diazonium salts (seventh entry). 

Acetylation of aniline produces acetanilide (2) and protects the amino group from the reagent to be used next. Treatment of 2 with chlorosulfonic acid brings about an electrophilic aromatic substitution reaction and yields/>-acetamidobenzene-sulfonyl chloride (3). Addition of ammonia or a primary amine gives the diamide, 4 (an amide of both a carboxylic acid and a sulfonic acid). Finally, refluxing 4 with dilute hydrochloric acid selectively hydrolyzes the carboxamide linkage and produces a sulfanilamide. (Hydrolysis of carboxamides is much more rapid than that of sulfonamides.)... 

Electrophilic aromatic substitution reactions are a very important class of chemical reactions that allow the introduction of substituents on to arenes by replacing a hydrogen atom covalently bonded to the aromatic ring structure by an electrophile. The most common reactions of this type are aromatic nitrations, halogenations, Friedel-Crafts alkylations and acylations, formylations, sulfonations, azo couplings and carboxylations - to name just a few. 

The electrophilic aromatic substitution reaction can be used to add bromo (-Br), chloro (-C1), nitro (-NO2), and sulfonic acid (-SO3H) groups to... 

As shown here, the sulfonyl chloride group (—SO2CI) can be conveniently introduced to an aromatic ring via an electrophilic aromatic substitution reaction using chlorosulfonic acid. The reaction is usually referred fo as chlorosul-fonation. It has been determined that two equivalents of fhe acid are required per equivalent of the aromatic compound. In the initial attack the system first forms the corresponding sulfonic acid, which in turn is converted to the sulfonyl chloride. If is believed fhat the initial stage of the reaction involves SO3 as the electrophile. It is likely that this reagent results from the establishment of fhe equilibrium reaction shown here ... 

Representative Electrophilic Aromatic Substitution Reactions of Benzene 457 Mechanistic Principles of Electrophilic Aromatic Substitution 458 Nitration of Benzene 459 Sulfonation of Benzene 461 Halogenation of Benzene 462 Biosynthetic Halogenation 464 Friedel-Crafts Alkylation of Benzene Friedel-Crafts Acylation of Benzene Synthesis of Alkylbenzenes by Acylation-Reduction 469 Rate and Regioselectivity in Electrophilic Aromatic Substitution 470 Rate and Regioselectivity in the Nitration ofToluene 472... 

The chemistry of aromatic compounds is dominated hy electrophilic aromatic substitution reactions, both in the laboratory and in biological pathways. Many variations of the reaction can be carried out, including halogenation, nitration, sulfonation, and hydroxylation. Friedel-Crafts alkylation and acylation, which involve reaction of an aromatic ring with carho-cation electrophiles, are particularly useful. 

Like benzene, substituted benzenes undergo the five electrophilic aromatic substitution reactions listed in Section 19.13 halogenation, nitration, sulfonation, and Friedel-Crafts acylation and aklyation. 

We can add a sulfonic acid group (—SO H) to an aromatic ring by an electrophilic aromatic substitution reaction called sulfonation. The reaction requires a mixture of SO and sulfuric acid, called fuming sulfuric acid. The electrophile is SO H. 

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