Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 15: Problem 33

The nitration of aniline takes place in acid. Under acidic conditions, the amino group must be largely protonated to give an anilinium ion, a meta- directing group. In fact, if the amino group is not acetylated, the product does contain substantial amounts of \(m\)-nitroaniline. Why is the product not entirely \(m\) nitroaniline?

Short Answer

Expert verified
Both protonated and unprotonated amino groups affect the nitration, leading to a mix of meta, ortho, and para products.

Step by step solution

01

- Understand Protonation

In acidic conditions, the aniline's amino group gets protonated to become an anilinium ion.
02

- Role of Anilinium Ion

The anilinium ion is a meta-directing group, meaning it directs the incoming nitro group to the meta position on the benzene ring.
03

- Examine Directing Groups

Consider that the amino group, when not protonated (if any remain unprotonated), is an ortho/para-directing group.
04

- Mixed Products

Due to the presence of some unprotonated amino groups, the nitration process will also result in ortho and para products.
05

- Conclusion

Thus, the product is not entirely meta-nitroaniline because both protonated (meta-directing) and unprotonated (ortho/para-directing) amino groups influence the nitration.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Protonation
Protonation is a fundamental concept in chemistry, where a proton (H+) is added to an atom, molecule, or ion.
For aniline, this occurs in acidic conditions. The nitrogen atom in the amino group of aniline (+NH2) gains a proton to form the anilinium ion (+NH3+).
The environment's acidity is crucial here. Acidic conditions are necessary to ensure protonation. This results in changes to the electron density and reactivity of the molecule.
In protonated form, the aniline now acts differently when it comes to electrophilic aromatic substitution reactions like nitration.
Meta-Directing Groups
Meta-directing groups are substituents on a benzene ring that direct incoming electrophiles to the meta position relative to themselves.
In the context of nitration, the anilinium ion (+NH3+) is a meta-directing group. This is because the protonated amino group withdraws electron density from the benzene ring primarily through resonance and inductive effects.
This withdrawal is strongest at the ortho and para positions, making the meta position relatively more electron-rich and favorable for the electrophilic attack.
That's why, in acidic conditions, nitration of aniline leads to the formation of meta-nitroaniline.
Ortho/Para-Directing Groups
Ortho/para-directing groups are the opposite of meta-directing groups. They push incoming electrophiles to the ortho and para positions on a benzene ring.
When an amino group (-NH2) is not protonated, it acts as an ortho/para director. This is due to its electron-donating properties.
Through resonance, the non-protonated amino group can donate electron density to the benzene ring, making the ortho and para positions more reactive.
As a result, in the presence of non-protonated amino groups, nitration will predominantly occur at the ortho and para positions, forming ortho and para-nitroaniline.
Anilinium Ion
The anilinium ion (+NH3+) forms when aniline is protonated in acidic conditions. This ion plays a crucial role in directing nitration.
The extra proton on the nitrogen atom creates a positively charged ion, which significantly impacts how the benzene ring interacts with electrophiles.
As a meta-directing group, the anilinium ion influences the nitration predominantly towards the meta position.
However, the mixture of protonated aniline (anilinium ion) and non-protonated aniline during the reaction contributes to various nitration products.
Mixed Nitration Products
Mixed nitration products arise due to the simultaneous presence of protonated (anilinium ion) and non-protonated amino groups in the reaction.
In acidic conditions, most amino groups are protonated, directing nitration to the meta position, creating meta-nitroaniline.
But some amino groups remain unprotonated due to incomplete protonation or reaction dynamics. These unprotonated amino groups are ortho/para-directing.
As a result, the nitration process leads to a mixture of products: meta, ortho, and para-nitroaniline. This explains why the product is not entirely meta-nitroaniline.

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Explain why 2-substitution is preferred to 3 -substitution in the \(\mathrm{S}_{\mathrm{E}} \mathrm{Ar}\) reaction of furan.

Devise syntheses of the following substituted benzenes. You may start from benzene, organic reagents containing no more than three carbons, and any inorganic reagents you may need.

Through a mechanistic analysis of the electrophilic aromatic substitution of acetamidobenzene, explain why this compound substitutes mainly para. Suggest a reason why the reaction rate of acetamidobenzene with electrophiles is slower than the rate of the reaction of aniline with electrophiles.

Suggest synthetic procedures leading to each of these compounds. You may start with benzene, any inorganic reagent, and organic compounds containing no more than five carbon atoms.

Design a synthesis of benzene starting from inorganic compounds and organic compounds containing only hydrogen and no more than four carbon atoms.
See all solutions

Recommended explanations on Chemistry Textbooks

Chemical Reactions

Read Explanation

Making Measurements

Read Explanation

Nuclear Chemistry

Read Explanation

Physical Chemistry

Read Explanation

Inorganic Chemistry

Read Explanation

The Earths Atmosphere

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free