The nitration of benzene is an electrophilic aromatic substitution reaction, in which a nitro group no 2 is introduced onto a benzene ring. Note that in this reaction and in others that follow, only one of the six benzene hydrogens is shown explicitly to emphasize that one hydrogen is lost in the reaction. The nitration of these compounds is carried out commercially in vapour phase at temperature of 350450 degree centigrade. Eas aromatic nitration reaction and mechanism video. Nitration of benzene mechanism in easy steps youtube. The sulfuric acid behaves as a catalyst, and allows this nitration reaction to proceed at a lower. However, this reaction proceeds slowly, which is inconvenient dangerous since hot, conc. The elctrophilic substitution reaction mechanism for nitration of benzene. Parrafins can be attacked by certain atoms and free radicals. The first reported nitration reaction was the nitration of benzene in red fuming nitric acid, in the first half of the xix century, by mitscherlich 1834. Substituents that cause this result are called mdirectors and they usually deactivate the ring. The mechanism is believed to proceed via an nnitropyridinium nitrate salt similar to the above mentioned nitration using dinitrogen pentoxide scheme 9 1993jcm156, 1995sl383. A substituent x is said to be activating if the rate of electrophilic aromatic substitution of the substituted benzene c 6h 5x is faster than benzene. Mechanism of nucleophilic addition reaction catalysed by alkalis.
This page gives you the facts and a simple, uncluttered mechanism for the electrophilic substitution reaction between benzene and a mixture of concentrated nitric acid and concentrated sulfuric acid. In aromatic nitration, aromatic organic compounds are nitrated via an electrophilic aromatic substitution mechanism involving the attack of the electronrich benzene ring on the nitronium ion. Nitric acid accepts a proton from sulphuric acid and then dissociates to form nitronium ion. Mechanism and regioselectivity of electrophilic aromatic. Nitration is a general class of a chemical process for the introduction of a nitro group into an organic chemical compound. Nitration of bromobenzene by electrophilic aromatic substitution important concepts electrophilic aromatic substitution reactions nitronium ion as an electrophile activating vs deactivating groups o,pdirectors vs meta directors using resonance structures to predict substitution pattern part a, p. The first step in the nitration of benzene is to activate hno 3with sulfuric acid to produce a stronger electrophile, the nitronium ion. The nitration process is a general class of chemical process for the introduction of a nitro group no 2 into an organic chemical compound. To get reaction on the pyridine ring, the noxide can be used as with pyridine itself. This can be done by reducing the nitro group into an amino group through the process of hydrogenation. In technical terms, nitration is actually part of a reaction type known as. Stationary points were located and characterized by the dft procedures at.
Electrophilic aromatic substitution nitration ucla chemistry. The source of the nitronium ion is through the protonation of nitric acid by sulfuric acid, which causes the loss of a water molecule and formation of a nitronium ion. Mechanism of nucleophilic addition reaction of aldehyde. This video also helps you understand the role of the acid catalyst before and during the reaction. Nitration of toluene electrophilic aromatic substitution. Pdf a theoretical study of the nitration of benzene by acyl nitrates catalyzed by. In the case of benzene, the hybrid structure is the one below the one you learn at school. H 2 so 4 here, h 2 so 4 acts as a an acid and hno 3 as a base entrancei chemistry doubts page consist of more questions for reference. Protonation of the hydroxy group of the nitric acid.
Benzene reacts with concentrated nitric acid at 323333k in the presence of concentrated sulphuric acid to form nitrobenzene. Nitration of bromobenzene is an electrophilic aromatic substitution reaction. Nitration of paraffinic compounds gas phase reaction unlike aromatic compounds the paraffinic compounds are quite inert to nitrating agent. Nitration is an example of electrophilic aromatic substitution. Nitration of benzene mechanism electrophilic aromatic substitution reactions duration. Facts and mechanism for the nitration of benzene an electrophilic substitution reaction between benzene and nitric acid. Aromatic nitration is the best way to introduce nitrogencontaining substituents into the benzene ring. A substituent x is said to be deactivating if the rate of electrophilic aromatic substitution of the substituted benzene c 6h 5x is slower than benzene.
This occurs following the interaction of two strong acids, sulfuric and nitric acid. Useful as a selective and mild nitration methodfor example, allowing. More loosely the term also is applied incorrectly to the different process of forming nitrate esters between alcohols and nitric acid, as occurs in the synthesis of nitroglycerin. The term is also applied somewhat incorrectly to the different process of forming nitrate esters between alcohol derivatives and nitric acid, as. If you want the nitration mechanism explained to you in detail, there is a link at the bottom of the page. When benzene is treated with concentrated nitric acid and concentrated sulphuric acid at below 55 o c temperature, nitrobenzene is formed. Nitration of benzene mechanism electrophilic aromatic. As the aromaticity of benzene is not disturbed in the reaction, these reactions are highly spontaneous in nature. Electrophilic substitution of benzene is the one where an electrophile substitutes the hydrogen atom of benzene. Loss of the leaving group, a water molecule provides the nitronium ion, the reactive electrophile.
Nitration of benzene firstly involves the formation of a very powerful electrophile, the nitronium ion, which is linear. Mechanism of aromatic nitration accounts of chemical. The overall reaction for the nitration of methyl benzoate. The nitronium ion acts as an electrophile in the process which further reacts with benzene to form an arenium ion. A reaction profile for the nitration of benzene with nitronium ion has been successfully calculated for the first time. This page gives you the facts and a simple, uncluttered mechanism for the electrophilic substitution reaction between benzene and a mixture of concentrated nitric acid and concentrated sulphuric acid. Electrophilic aromatic nitration is one of the most thoroughly studied classes of organic reactions, and its mechanism has been intensely debated over many decades 1,2,3,4,5,6,7. It is generated from a lewis base, nitric acid, in the presence of a lewis acid catalyst, sulfuric acid. The formation of a nitronium ion the electrophile from nitric acid and sulfuric acid is shown below.
The real structure is an intermediate of these structures represented by a resonance hybrid. Sulfuric acid is the stronger acid and it protonates the nitric acid on the oh group so that a molecule of water can leave. This page gives you the facts and a simple, uncluttered mechanism for the electrophilic substitution reaction between. Benzene reactions sulphonation of benzene and nitration of.
Directing effects of substituents when a monosubstituted benzene undergoes an electrophilic aromatic substitution reaction, three possible disubstitution products might be obtained. This ion is formed by the reaction between the concentrated nitric acid and concentrated sulphuric acid. Basic examples of electrophilic substitution reaction of benzene are nitration, sulfonation, halogenation, friedel. Full text get a printable copy pdf file of the complete article 993k, or click on a page image below to browse page by page. Nitration methods and mechanisms pdf xii 330 pp, dm. Dft study on nitration mechanism of benzene with nitronium. If we increase the temperature there is a greater chance of entering more than one nitro group in the benzene ring. Mechanism of nucleophilic addition reaction of carbonyl group.
Benzene reactions sulphonation of benzene and nitration. In the first step, an intermediate is formed by nucleophilic attack of the benzene to the nitronium ion. Nitration, sulphonation and halogenation class 11 notes. Nitration methods and mechanisms pdf nitration methods and mechanisms pdf nitration methods and mechanisms pdf download. Nitration is important synthetically because it is one of the best ways to add an amino group to a benzene ring. Organic chemistry eas aromatic nitration reaction and mechanism tutorial video this video shows you a step by step mechanism for the formation of nitronium, which is the super electrophile that is attacked by benzene in the nitration reaction. More recently, solid acid catalysts have been used with nitric acid for nitration of aromatic compounds, including pyridine. Thermal free radical nitration of benzene and toluene with tetranitromethane in sharp contrast gave nearly statistical product distributions. As mentioned above, nitration simply means that we are adding a nitro group to an aromatic or benzene ring. Vogels elementary practical organic chemistry, longman group ltd. In spite of that, the reaction follows a different mechanism from the one in a. The elctrophilic substitution reaction mechanism for nitration of benzene the formation of the electrophile. Lab report 11 nitration of methylbenzoate ch 238 uab. The reaction is regioselective and produces predominantly methyl 3nitrobenzoate.
This is one of many videos provided by clutch prep to prepare you to succeed in your college. The nitration of a benzene ring is an electrophilic aromatic substitution reaction, andits general mechanism is summarized in figure 2. Bromine itself is not electrophilic enough to react with benzene. All electrophilic aromatic substitution reactions occur by similar mechanisms. A good example is acridine, with two benzene rings, which gives four nitration products, all on the benzene rings. Reactions of aromatic compounds rutgers university. Nitration of bromobenzene by electrophilic aromatic. If you substitute a nitro group, no 2, into the benzene ring in methylbenzene, you could possibly get any of the following products the carbon with the methyl group attached is thought of as the number 1 carbon, and the ring is then numbered around from 1 to 6. This organic chemistry video tutorial provides a basic introduction into the nitration of benzene mechanism which is one of the most common. In the second step, this intermediate is deprotonated by water and nitrobenzene is obtained.
Pdf a dft study of nitration of benzene by acyl nitrate catalyzed. Nitration is the substitution of an no 2 group for one of the hydrogen atoms on a benzene ring. Nitration reactions can proceed via a free radical and an ionic mechanism olah et al. Mechanism of nucleophilic addition reaction of ketone. In this experiment the students nitrate methyl benzoate. Electrophilic and free radical nitration of benzene and. Nitration and sulfonation of benzene chemistry libretexts.
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