There are 6 nucleophilic substitution mechanisms encountered with aromatic systems. Files are available under licenses specified on their description page. Chem 202 electrophilic aromatic substitution worksheet give the major product of the following reactions. Media in category electrophilic aromatic substitution reactions the following 95 files are in this category, out of 95 total. Using the drawing window on the left below, draw the major product from each of the electrophilic aromatic substitution reactions shown below. In electrophilic aromatic substitution reactions the hydroxyl group is an o,pdirector because. King chapter 18 electrophilic aromatic substitution i. Electrophilic aromatic substitution is a multistep process. Aromatic compounds react by electrophilic aromatic substitution reactions, in which the aromaticity of the ring system is preserved. This page was last edited on 3 november 2014, at 16.
A substituent affects two aspects of the electrophilic aromatic substitution reaction. Di and trifluorobenzenes in reactions with me 2 em e p, n. Electrophilic aromatic substitution study guide cheat sheet. All structured data from the file and property namespaces is available under the creative commons cc0 license. Electrophilic aromatic substitution reactions are one of the more fun topics that you will study in organic chemistry. Electrophilic aromatic substitution the most characteristic reaction of aromatic compounds is electrophilic aromatic substitution, in which one of the ring hydrogens is substituted by a halogen, nitro group, sulfonic acid group, alkyl or acyl group. The s rn 1 mechanism was proposed for the first time in 1966 for the substitution of alkyl halides with electronwithdrawing groups and in 1970 for the substitution of unactivated aryl halides. Nucleophilic aromatic substitution for hydrogen reduction in chemical waste generation elimination of 74% of organic waste 99% of inorganic waste eliminates use of chlorine reduction in waste water more than 97% savings eliminates use of xylene a sara chemical improves process safety lower reaction temperatures. Jun 04, 20 reflecting the key role played by these species as intermediates in most snar reactions, chapter 2 then discusses the chemistry of anionic sigmacomplexes. Chemistry of aromatic compounds prefacegeneral introduction to sch 302 the course deals with benzene, its derivatives and other benzenoid compounds. Understand and be able to draw the mechanism of an electrophilic aromatic substitution. Concerted nucleophilic aromatic substitutions nature chemistry.
We herein report results obtained from an integrated experimental and theoretical study on aromatic nucleophilic substitution snar reactions of a series of amines towards 1fluoro2,4. Aromatic hydrocarbons are compounds that contain a benzene ring. Y by an electrophile e such that e becomes bonded to y by the electron pair of the xy bond. Aromatic substitution molecules chemical reactions. The most characteristic reaction of aromatic compounds is electrophilic aromatic substitution, in which one of the ring hydrogens is substituted by a halogen, nitro. Copper reagents have been used in some cases in classical procedures for the formation of products from aromatic substitution. Xray crystallography of several products revealed that the compounds containing oxygen and nitrogen heteroatoms are highly planar and engage. The structure and properties of aromatic systems were discussed in chapter 11. B it donates electron density to the ring by resonance and. In the first step, the addition of an electrophile yields a highenergy carbocation in which the aromatic. Final exam problems ch 1416 conjugated and aromatic diels alder problem set 1 diels alder problem set 2 aromatic reactions aromatic reagents nomenclature problems aromatic synthesis problems more synthesis problems even more synthesis problems. Since then, the scope of the process has increased considerably, and it constitutes an important synthetic method for achieving the substitution of unactivated aromatic and heteroaromatic. Final exam problems ch 1416 conjugated and aromatic diels alder problem set 1 diels alder problem set 2 aromatic reactions aromatic reagents nomenclature problems aromatic synthesis problems more synthesis problems even more synthesis problems summary of aromatic theory topics. Since the reagents and conditions employed in these reactions are electrophilic, these reactions are commonly referred to as electrophilic aromatic substitution.
A synthetic approach for preparing a variety of heterocyclic tetrahydropentacene derivatives via nucleophilic aromatic substitution reactions of bidentate nucleophiles and tetrafluoroterephthalonitrile was developed. Aromatic substitution reaction free download as powerpoint presentation. Its electrophilic substitution with bromine is only compatible in the presence of some strong lewis acid. For example, we know alkenes can be oxidized to syn diols kmno 4 and undergo electrophilic additions with halogens br 2. This transformation takes place through electron transfer steps with radicals and radical anions as intermediates. Examples of electrophilic aromatic substitution reactions s. Reagent substrate reactive intermediate type of organic substitution nucleophilic aliphatic carbocation aliphatic nucleophilic substitution electrophilic aromatic carbanion aromatic electrophilic substitution free radical substitution. Chapter 17 reactions of aromatic compounds electrophilic. Reflecting the key role played by these species as intermediates in most snar reactions, chapter 2 then discusses the chemistry of anionic sigmacomplexes. Electrophilic aromatic substitution is an organic reaction in which an atom that is attached to an aromatic system usually hydrogen is replaced by an electrophile. Electrophilic aromatic substitution is a general reaction of all aromatic compounds, including polycyclic aromatic hydrocarbons, heterocycles, and substituted benzene derivatives. Aromatic substitution by the srn1 reaction organic. While some problems remain, the broad mechanistic outlines of these reactions are securely established at present.
In many cases these coppermediated reactions occur at high temperatures and are substrate dependent. Reactions of aromatic compounds introduction to chemistry. Modern nucleophilic aromatic substitution wiley online books. The most important group of such reactions are the electrophilic aromatic substitutions, but there are also significant reactions that take place by nucleophilic mechanisms, and still others that involve radical processes. A reaction map pdf for benzene and aromatic compounds. Many other substitution reactions of benzene have been observed, the five most useful are listed below chlorination and bromination are the most common halogenation reactions. The most important group of such reactions are the electrophilic aromatic substitutions, but there are also significant reactions that take place by nucleophilic. What are the major products of the following reactions. The most important of these is the s n ar mechanism, where electron withdrawing. A it donates electron density to the ring by induction and destabilizes the meta sigma complex. A functional group is a substituent that brings with it certain chemical reactions that the aromatic compound itself doesnt display the bromination of benzene. Electrophilic aromatic substitution eas represents one of the most important classes of reactions in all of chemistry.
Electrophilic aromatic substitution reactions the general picture an example of an sear reaction can be found in the biosynthetic. Electrophilic aromatic substitution video khan academy. These compounds comprise a distinct class, called aromatic hydrocarbons. A nucleophilic aromatic substitution is a substitution reaction in organic chemistry in which the nucleophile displaces a good leaving group, such as a halide, on an aromatic ring.
The arene system contains an electron rich cc system which react with electrophiles via a substitution pathway to preserve aromaticity via what is known as electrophilic aromatic substitution ears. Aromaticity and electrophilic aromatic substitution. Pdf specific nucleophileelectrophile interactions in. Many reactions common to alkenes carboncarbon double bonds also function in a similar fashion with the double bonds in aromatic compounds, though generally the activation barrier is higher due to the stabilizing force of aromaticity ca. In this report, we present unique examples of electrondeficient arenes instead undergoing. Bromination follows the same general mechanism for the electrophilic aromatic substitution eas. Direct aromatic substitution of unactivated aryl halides is slow and generally requires a catalyst to become a useful synthetic method. Next we consider a class of hydrocarbons with molecular formulas like those of unsaturated hydrocarbons, but which, unlike the alkenes, do not readily undergo addition reactions. For example, benzene reacts with bromine to form bromobenzene. Such a reaction is not favorable, thermodynamically. Predominant electrophilic aromatic substitution reactions patterns, effect of substituent on the rates of reaction and orientation of incoming substituent are discussed.
Consider electrophilic aromatic substitution on the compound trans2methoxyethenylbenzene a. The substitution reactions of aromatic systems by electrophilic and by nucleophilic reagents have been subjected to detailed quantitative study extending over a number of years. In the reaction with alkyl halides, they can also promote elimination reactions rather than substitution. In a substitution reaction, a functional group in a particular chemical compound is replaced by another group. Arrange the following products according to the % yield obtained from the nitration of tbutylbenzene. Feb 21, 20 aromatic nucleophilic substitution reaction 1. H3co i would you expect the aromatic ring in compound a to be choose one. And so, in addition to my eas tutorial video series ive put together a thorough eas cheat sheet.
Electrophilic substitution reactions for nitrobenzene are 100,000 times slower than for benzene. Some of the most important electrophilic aromatic substitutions are aromatic nitration, aromatic halogenation, aromatic sulfonation, and alkylation and alkylating friedelcrafts reaction. Nomenclature of benzene and its derivatives are dealt with in details since this will form some. View benzene structure, reactions and substitution. Aromatic substitution an overview sciencedirect topics. Throughspace activation can override substituent effects. General mechanism of electrophilic aromatic substitution, halogenation, nitration, sulfonation, friedelcrafts alkylation and acylation. Many functional groups can be added to aromatic compounds via electrophilic aromatic substitution reactions. But perhaps you find it tricky due to the sheer volume of information that makes up the big picture. An example of an aromatic substitution reaction is shown below. Substitution reactions in aromatic compounds nptel. By contrast, the substitution reactions of aromatic.
Electrophilic aromatic substitution chemistry libretexts. The product mix contains mostly the meta isomer, only small. Structure of benzene, aromaticity of benzene and related compounds will form the first part of the course. Aromatic substitution free download as powerpoint presentation. Reagents that acquire an electron pair in chemical reactions are said to be electrophilic electronloving. Microwaveassisted chemistry study questions 1 the solvent for the reactions with ethylamine or aniline is ethanol, but the solvent for the reaction with potassium thiocyanate is a mixture of water and ethanol. We can picture this in a general way as a heterolytic bond breaking of compound x. This chapter is concerned with reactions that introduce or interchange substituent groups on aromatic rings. All electrophilic aromatic substitution reactions share a common mechanism.
Porter, in comprehensive heterocyclic chemistry, 1984. Electrophilic aromatic substitution and substituted benzenes. Eas reaction, nucleophilic aromatic substitution snar, and. One of the iron laws of eas is that an electronrich aromatic ring will react more rapidly than an electronpoor ring with suitable electrophiles. Snar mechanism simple aryl halides, are relatively unreactive toward nucleophilic substitution under conditions that would give rapid nucleophilic substitution with alkyl halides. Final exam problems ch 1416 conjugated and aromatic.
Concerted nucleophilic aromatic substitutions nature. When attempting to conduct a nucleophilic aromatic substitution of chlorobenzene see reaction below you notice that adding electronwithdrawing groups increases the rate of reaction and decreases temperature at which the reaction needs to be ran. Chem 202 electrophilic aromatic substitution worksheet. Homolytic aromatic substitution of the diazines and benzodiazines appears to have been a little used phenomenon and information on such reactions in the pyrazine, quinoxaline and phenazine series is scarce, although in the case of pyrazine and quinoxaline the positions. Electrophilic aromatic substitution electrophilic aromatic substitution. Chapter 3 describes the concept of superelectrophilicity in snar substitutions, as it has recently emerged from the reactivity of strongly electrondeficient aromatic and heteroaromatic. Orgo2 ch19 aromatic substitution reactions practice test.
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