Electrophilic aromatic substitution alkylation Halogenation

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

Equipped with these reference trends for steric and electronic effects, one is prepared to survey more general classes of electrophilic aromatic substitution on benzocycloalkenes. Such reactions include nitration, halogenation, sulfonation, and alkylation. Each has its own mechanistic peculiarities, but their product distributions can be rationalized by consideration of the appropriate reference. 

Electrophilic aromatic substitution is a reaction where a hydrogen atom in an aromatic system, e.g. benzene, is replaced by an electrophile. Some of the important electrophilic substitution reactions are Friedel-Crafts alkylation and acylation, nitration, halogenation and sulphonation of benzene. 

Reactions include electrophilic aromatic substitution te.g.. halogenation. nitration. C-acylalion. and alkylation). /V-alkylation. arylulinn. I it hut am and subsequent transformations, and oxidation. 

Predict products and propose mechanisms for the common electrophilic aromatic substitutions halogenation, nitration, sulfonation, and Friedel-Crafts alkylation and acylation. Problems 17-44, 47, 48, 51, 59, G4, and 70... 

Many substituted benzene rings undergo electrophilic aromatic substitution. Common substituents include halogens, OH, NH2, alkyl, and many functional groups that contain a carbonyl. Eiach substituent either increases or decreases the electron density in the benzene ring, and this affects the course of electrophilic aromatic substitution, as we will learn in Section 18.7. 

These solid-acid catalysts are, in principle, applicable to a plethora of acid-catalyzed processes in organic synthesis [18]. These include various electrophilic aromatic substitutions, e.g. nitrations, halogenations, and Fiiedel-Crafts alkylations and acylations, and numerous rearrangement reactions such as the Beckmann and Fries rearrangements. Other examples include a variety of cyclization reactions such as Diels-Alder reactions and the synthesis of pyridines and other heterocycles. 

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... 

Certain compounds (electrophilic) can react with phenols (nucleophilic). The nucleophilic activity can be either in the iaromatic ring or the oxygen in the hydroxyl group. Examples of electrophilic aromatic substitution include nitration, halogenation, Friedel-Crafts reactions (alkylation and acylation), and sulfonation. The halogenation example shown below is a polysubstitution reaction involving bromine. The polysubstitution usually occurs when polar solvents are used. 

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 five types of electrophilic aromatic substitution discussed here are nitration, halogenation, sulfonation, Friedel-Crafts alkylation, and Friedel-Crafts acylation. 

We have seen several examples of reactions in which two reactants give not a single product but mixtures. Examples include halogenation of alkanes (eq. 2.13), addition to double bonds (eq. 3.31), and electrophilic aromatic substitutions (Sec. 4.11), where more than one isomer may be formed from the same two reactants. Even in nucleophilic substitution, more than one substitution product may form. For example, hydrolysis of a single alkyl bromide gives a mixture of two alcohols in eq. 6.14. But sometimes we find two entirely different reaction types occurring at the same time between the same two reactants, to give two (or more) entirely different types of products. Let us consider one example. 

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