Nitration of MethylBenzoate and Nitration of Bromobenzene

The Organic Chemistry Tutor
8 May 201814:13
EducationalLearning
32 Likes 10 Comments

TLDRThis chemistry video delves into the nitration process of methyl benzoate and bromobenzene. It explains the meta-directing effect of the ester group in methyl benzoate, leading to the major product's formation through a detailed mechanism involving the nitronium ion. The script also covers the ortho and para directing nature of bromine in bromobenzene, illustrating how different products arise from the nitration reaction. The video provides a clear understanding of the electron-withdrawing influence of substituents on the benzene ring and the subsequent reaction mechanisms.

Takeaways
  • 🧪 The video discusses the nitration of methyl benzoate and bromobenzene, focusing on the major products and the positions of the NO2 group on the benzene ring.
  • 🔍 When reacting methyl benzoate with nitric acid and sulfuric acid, the NO2 group will be added to the meta position due to the meta-directing effect of the ester group.
  • 🌀 The carbonyl group in methyl benzoate withdraws electrons through resonance, making the ortho and para positions electrophilic and less likely to react with the nitronium ion.
  • 📚 The mechanism of nitration involves the protonation of nitric acid to form a good leaving group, followed by the formation of the nitronium ion which acts as the electrophile.
  • ⚔️ The meta carbon on the benzene ring is the most nucleophilic due to its neutral state, making it the preferred site for the NO2 group attachment.
  • 🌟 The final product of the nitration of methyl benzoate is shown, with the NO2 group attached to the meta position.
  • 🌊 In the case of bromobenzene, the bromine atom acts as a weak deactivator but an ortho-para director, leading to the possibility of ortho or para substitution.
  • 🔄 The resonance structure of bromobenzene explains why the NO2 group can attack the ortho position, creating ortho-bromo nitrobenzene.
  • 🔄 Similarly, a resonance structure can be drawn to show the attack of the NO2 group at the para position, resulting in para-bromo nitrobenzene.
  • 🛠️ The mechanism for the formation of both ortho and para products involves the use of a base to remove a hydrogen atom and regenerate the aromatic ring.
  • 📝 The video script provides a detailed step-by-step explanation of the nitration reactions, including the intermediate steps and the final products.
Q & A

  • What is the main reaction discussed in the video script?

    -The main reaction discussed in the video script is the nitration of methyl benzoate and bromobenzene.

  • What group is added to the benzene ring during the nitration of methyl benzoate?

    -An NO2 group is added to the benzene ring during the nitration of methyl benzoate.

  • Why does the NO2 group preferentially go to the meta position in the nitration of methyl benzoate?

    -The NO2 group prefers the meta position because the carbonyl group of the ester withdraws electrons from the ring through resonance, making the ortho and para positions electrophilic and less nucleophilic, while the meta position remains more nucleophilic.

  • What is the role of sulfuric acid in the nitration reaction discussed in the script?

    -Sulfuric acid is used to protonate nitric acid, turning it into a good leaving group and facilitating the formation of the nitronium ion, which is the electrophile in the nitration reaction.

  • How does the presence of the ester group affect the nitration of methyl benzoate?

    -The ester group, being electron-withdrawing, directs the nitration to the meta position through resonance stabilization, making the ortho and para positions less favorable for electrophilic attack.

  • What is the electrophile in the nitration reaction of both methyl benzoate and bromobenzene?

    -The electrophile in the nitration reaction of both methyl benzoate and bromobenzene is the nitronium ion (NO2+).

  • What are the two possible products of the nitration of bromobenzene?

    -The two possible products of the nitration of bromobenzene are ortho-bromo nitrobenzene and para-bromo nitrobenzene.

  • Why is bromine an ortho-para director in the nitration of bromobenzene?

    -Brominated benzene is an ortho-para director because the lone pair of electrons on the bromine atom can participate in resonance, making the ortho and para positions more nucleophilic and thus more likely to be attacked by the nitronium ion.

  • What is the significance of the acidic hydrogen in the mechanism of nitration?

    -The acidic hydrogen is significant because it is removed by a base to regenerate the aromatic ring, which is essential for the stability of the intermediate formed during the nitration process.

  • How does the video script explain the formation of the ortho-bromo nitrobenzene product?

    -The formation of ortho-bromo nitrobenzene is explained by the resonance stabilization of the ortho position due to the bromine atom, which makes it nucleophilic and more likely to be attacked by the nitronium ion.

  • What is the role of the base in the final step of the nitration mechanism?

    -The base in the final step of the nitration mechanism removes the acidic hydrogen from the intermediate, allowing the pi bond to reform and completing the formation of the nitro-substituted product.

Outlines
00:00
🧪 Nitration of Methyl Benzoate Mechanism

This paragraph discusses the nitration reaction of methyl benzoate with nitric acid and sulfuric acid, focusing on the major product formed. The reaction involves the addition of an NO2 group to the benzene ring, which is predicted to occur at the meta position due to the meta-directing effect of the ester group. The carbonyl group withdraws electrons, making the ortho and para positions electrophilic and less likely to react with the nitronium ion electrophile. The mechanism is detailed, starting with the protonation of nitric acid to form the nitronium ion, followed by its attack on the meta carbon of the benzene ring. A base is then used to remove a hydrogen atom, regenerating the aromatic system and yielding the final product.

05:04
🌟 Nitration of Bromobenzene: Ortho and Para Products

The second paragraph explores the nitration of bromobenzene, which is a weak deactivator and an ortho-para director. Two possible products are ortho-bromo nitrobenzene and para-bromo nitrobenzene. The mechanism for the formation of these products is explained through resonance structures, showing how the bromine atom influences the reaction at the ortho and para positions. The ortho product is formed when the NO2 group attacks the ortho carbon, which is made nucleophilic by the resonance of the bromine lone pair. The para product is formed through a similar process, but with the nucleophilic attack occurring at the para position. Both mechanisms conclude with the use of a base to remove a hydrogen atom and restore the aromatic system.

10:05
🔍 Detailed Mechanism for Para-Bromo Nitrobenzene Formation

This paragraph delves deeper into the formation of para-bromo nitrobenzene. It begins with the resonance stabilization of the benzene ring with a bromine atom, which leads to the nucleophilic attack of the NO2 group at the para position. The mechanism involves the movement of double bonds and the use of a base to abstract a proton, resulting in the formation of the para product. The paragraph also emphasizes the importance of charge distribution and the role of the bromine atom in the reaction, highlighting the final neutral state of the bromine and the restoration of the aromatic system with three double bonds.

Mindmap
Keywords
💡Nitration
Nitration is a chemical reaction that involves the introduction of a nitro group (-NO2) into an organic compound. In the context of the video, nitration is the process of adding a nitro group to methyl benzoate and bromobenzene, which is central to the discussion of the reaction mechanisms and the resulting products.
💡Methyl Benzoate
Methyl benzoate is an ester derived from benzoic acid and methanol. It is the starting compound in the first reaction discussed in the video. The reaction of methyl benzoate with nitric and sulfuric acids leads to the formation of a nitro compound, illustrating the concept of electrophilic substitution on an aromatic ring.
💡Bromobenzene
Bromobenzene is an aromatic compound in which one hydrogen atom of benzene is replaced by a bromine atom. It is the substrate for the second nitration reaction in the video, demonstrating how the presence of a bromine atom influences the position of the nitro group attachment.
💡Electrophilic Substitution
Electrophilic substitution is a type of chemical reaction where an electrophile (a substance that is electron-deficient) reacts with a nucleophile (a substance that is electron-rich), resulting in the substitution of an atom or a group in the nucleophile. The video explains how the nitronium ion acts as an electrophile in the nitration of both methyl benzoate and bromobenzene.
💡Meta-Direction
Meta-direction refers to the tendency of certain substituents on a benzene ring to direct incoming substituents to the meta position (the carbon atom separated by one carbon from the substituent). In the video, the ester group attached to the benzene ring in methyl benzoate is described as meta-directing, leading to the formation of a meta-substituted product.
💡Resonance
Resonance is a concept in chemistry that describes the delocalization of electrons within a molecule, allowing for the distribution of electrons over more than one possible position. The video uses resonance to explain the intermediate steps in the nitration reactions, particularly how the electron-withdrawing effect of the carbonyl group influences the reaction.
💡Nitronium Ion
The nitronium ion (NO2+) is the electrophile involved in nitration reactions. The video describes its formation from nitric acid and sulfuric acid and its subsequent reaction with the aromatic rings of methyl benzoate and bromobenzene, leading to the attachment of the nitro group.
💡Ortho-Position
The ortho-position is the carbon atom adjacent to the position of a substituent on a benzene ring. The video discusses how the bromine atom in bromobenzene can direct the nitro group to the ortho-position, resulting in ortho-bromo nitrobenzene.
💡Para-Position
The para-position is the carbon atom directly opposite to the position of a substituent on a benzene ring. The video explains that, in addition to the ortho-position, the bromine atom can also direct the nitro group to the para-position, leading to the formation of para-bromo nitrobenzene.
💡Aromaticity
Aromaticity is a property of cyclic, planar, and conjugated pi systems that have specific stability due to their delocalized electrons. The video mentions the importance of aromaticity in the mechanism of nitration, as the loss of aromaticity leads to an unstable intermediate that is highly reactive and seeks to regain its aromatic state by expelling a proton.
💡Electron Withdrawing Group
An electron withdrawing group is a functional group that can pull electron density away from the rest of the molecule through resonance. In the video, the carbonyl group of the ester in methyl benzoate is described as an electron withdrawing group, which influences the site of nitro group attachment by making the meta-carbon more nucleophilic.
Highlights

The video focuses on the nitration of methyl benzoate and bromobenzene.

Methyl benzoate reacts with nitric and sulfuric acid to add an NO2 group to the benzene ring.

The major product of the reaction is determined by the meta-directing effect of the ester group.

The carbonyl group withdraws electrons via resonance, affecting the reactivity of the benzene ring.

The meta carbon is the most nucleophilic due to its lack of positive charge.

The mechanism of nitration involves protonation of nitric acid and formation of the nitronium ion.

The nitronium ion acts as the electrophile in the reaction with methyl benzoate.

A generic base is used to abstract the acidic hydrogen, regenerating the aromatic ring.

The final product of methyl benzoate nitration is presented.

Bromobenzene's nitration can lead to ortho or para products due to bromine's ortho-para directing effect.

Resonance structures explain why the NO2 group can attack ortho and para positions.

The ortho product formation involves nucleophilic attack by the ortho carbon on the nitronium ion.

The para product formation involves nucleophilic attack by the peri carbon.

A base is used to remove the hydrogen from the intermediate to complete the reaction.

The ortho and para bromo nitrobenzene products are distinguished by the position of the NO2 group.

Charge distribution and the role of the bromine atom in the reaction mechanism are discussed.

The video concludes with a summary of the mechanisms for the formation of ortho and para bromo nitrobenzene.

Transcripts

Browse More Related Video

Ortho Para Ratio - Aromatic Nitration of Toluene

Friedel-Crafts Acylation

Nitration of Benzene Mechanism - Electrophilic Aromatic Substitution Reactions

Ortho Meta Para Directors - Activating and Deactivating Groups

More EAS - Electron Donating and Withdrawing Groups: Crash Course Organic Chemistry #38

Diels Alder Reaction

Rate This

5.0 / 5 (0 votes)

Thanks for rating:

Related Tags
Nitration ChemistryMethyl BenzoateBromobenzeneElectron WithdrawalMeta-DirectionNitronium IonAromatic StabilityOrtho-Para DirectorReaction MechanismChemical Education