Careers360 Logo
Hoffmann Bromamide Reaction Mechanism

Hoffmann Bromamide Reaction Mechanism

Edited By Team Careers360 | Updated on Jul 02, 2025 04:57 PM IST

Hoffmann degradation

The Hofmann rearrangement process is also known as Hofmann degradation is an organic reaction through which primary amide is converted to primary amine and the product formed will contains one fewer carbon atom than parent contains. This reaction includes oxidation of nitrogen that will be followed by rearrangement of carbonyl molecule and nitrogen to form an isocyanate intermediate. And this reaction will forms a wide range of products which also includes alkyl and aryl amines.

This Story also Contains
  1. Hoffmann degradation
  2. Q- Amides to amine reaction name ?
  3. Q- Hoffmann reaction?
  4. Hoffmann reaction
  5. Q- Hoffmann bromamide degradation reaction ?
  6. Hoffmann Bromamide Reaction Mechanism
  7. Uses of Hoffmann bromamide degradation reaction are:-

Q- Hoffman bromamide degradation reaction is shown by ?

Hoffmann bromamide degradation reaction is shown by amides

Also read -

Background wave

Q- Mendius reaction ?

In this reaction an organic nitrile is being reduced with the help of nascent hydrogen into a primary amine i.e.

RCN+2H2 → RCH2NH2

Mechanism of Hoffmann bromamide reaction will include an alkali that will be a strong base for the attack to amide, which then leads to the deprotonation and that will result in generation of an anion. This reaction is commonly used in the conversion of a primary amide into a primary amine that will contain one less carbon atom. This reaction will be processed when heating the primary amide along with a mixture of a halogen that may be chlorine or bromine, with a strong base and universal solvent i.e. water.

RCONH2 + Br2 + 4NaOH ? R-NH2 + Na2CO3 + 2NaBr + 2H2O

Q- Amides to amine reaction name ?

hoffmann bromamide reaction or Hoffman bromamide degradation reaction

Q- Hoffmann reaction?

It is the reaction between bromine with sodium hydroxide and product formed will be sodium hypobromite when performed in situ with proper procedure product will transformed to primary amide and then to an intermediate i.e. isocyanate. The production of an intermediate i.e. nitrene is impossible because it will also leads to the formation of a hydroxamic acid in the form of byproduct. And the intermediate i.e. isocyanate will further hydrolyze to form a primary amine, and in this process carbon dioxide will also be released.

NCERT Chemistry Notes:

Q- Sodium hypobromite formula?

NaBrO

Here Na is sodium

Br is bromine

And O is oxygen

Primary amines that will be produced through this technique will not be contaminated by any of the secondary or tertiary amines. Another name of this reaction is Hoffmann degradation of amide. The reaction of bromine and sodium hydroxide will lead to the production of sodium hypobromite that will in turn change the primary amide into an intermediate of isocyanate.

And the isocyanate intermediate will now be attacked by water, that will lead to many proton evolving steps. And the thermal conditions that will be responsible for the explosion of carbon dioxide gas and also responsible for the quenching of ammonium cation that is formed due to the attack of water on the isocyanate intermediate and the quenching will lead to the required amine product.

Hoffmann reaction

Hoffmann bromamide reaction will include an alkali that will be a strong base for the attack to amide, which then leads to the deprotonation and that will result in generation of an anion. This reaction is commonly used in the conversion of a primary amide into a primary amine that will contain one less carbon atom. This reaction will be processed when heating the primary amide along with a mixture of a halogen that may be chlorine or bromine, with a strong base and universal solvent i.e. water.

Q- Hoffmann bromamide degradation reaction ?

The Hofmann rearrangement process is also known as Hofmann degradation is an organic reaction through which primary amide is converted to primary amine and the product formed will contains one fewer carbon atom than parent contains. This reaction includes oxidation of nitrogen that will be followed by rearrangement of carbonyl molecule and nitrogen to form an isocyanate intermediate. And this reaction will forms a wide range of products which also includes alkyl and aryl amines.

NEET Highest Scoring Chapters & Topics
This ebook serves as a valuable study guide for NEET exams, specifically designed to assist students in light of recent changes and the removal of certain topics from the NEET exam.
Download EBook

Hoffmann Bromamide Reaction Mechanism

1st step – The hydroxide ion that have to be comes from the strong base will attacks the amide which causes the amide to deprotonates and then leads to the formation of water with the anion of amide.

2nd step – The anion will now attacks the diatomic bromine and leads to an alpha substitution reaction which results in the breakdown of bromine-bromine bond and N-Bromamide molecule will be formed along with Br- anion.

3rd step – The base will again attacks N-Bromamide that is formed in 2nd step and leads to its deprotonation which will results in the formation of water along with the formation of bromamide anion.

4th step – and the bromamide anion that is formed will goes through the process of rearrangement in such a way that the presence of ethyl group or any other R- group that is bonded through the carbonyl carbon will now forms bonds with the nitrogen. And also the bromide anion that is formed will leave the compound. This process will lead to the production of an isocyanate.

5th step – when the process hydrolysis i.e. water addition will takes place in isocyanate then this process will leads to the formation of carbamic acid and the pathway that will be followed in this process is nucleophilic addition reaction.

6th step – The carbamic acid that is formed in 5th step will now going to loses a carbon dioxide molecule, and forms a negative charge along with nitrogen i.e. bonded with one hydrogen and the ethyl group. When this molecule will be protonated through water, then the required primary amine will be formed.

RCONH2 + Br2 + 4NaOH ? R-NH2 + Na2CO3 + 2NaBr + 2H2O

Hoffmann bromamide reaction

The Hofmann rearrangement process is also known as Hofmann degradation is an organic reaction through which primary amide is converted to primary amine and the product formed will contains one fewer carbon atom than parent contains. This reaction includes oxidation of nitrogen that will be followed by rearrangement of carbonyl molecule and nitrogen to form an isocyanate intermediate. And this reaction will forms a wide range of products which also includes alkyl and aryl amines.

Also Read:

Uses of Hoffmann bromamide degradation reaction are:-

  • It is used in the production of primary aromatic amine and aliphatic amines.

  • It is also used for the preparation of aniline molecules.

  • It also plays an important role in the production of anthranilic acid and phthalimide.

  • 3-Aminopyridine is also formed by this reaction through nicotinic acid.

  • Hoffmann reaction will not be able to change the symmetrical structure of the compound i.e. phenyl propanamide.

  • Hoffmann bromamide degradation

  • Mechanism of Hoffmann bromamide reaction will include an alkali that will be a strong base for the attack to amide, which then leads to the deprotonation and that will result in generation of an anion. This reaction is commonly used in the conversion of a primary amide into a primary amine that will contain one less carbon atom. This reaction will be processed when heating the primary amide along with a mixture of a halogen that may be chlorine or bromine, with a strong base and universal solvent i.e. water.

  • RCONH2 + Br2 + 4NaOH ? R-NH2 + Na2CO3 + 2NaBr + 2H2O

Q- Hofmann rearrangement ?

The Hofmann rearrangement process is also known as Hofmann degradation is an organic reaction through which primary amide is converted to primary amine and the product formed will contains one fewer carbon atom than parent contains. This reaction includes oxidation of nitrogen that will be followed by rearrangement of carbonyl molecule and nitrogen to form an isocyanate intermediate. And this reaction will forms a wide range of products which also includes alkyl and aryl amines.

Also check-

Frequently Asked Questions (FAQs)

1. What is the main difference between the Hoffmann bromamide reaction and the Hofmann rearrangement?
The main difference is that the Hoffmann bromamide reaction results in a primary amine with one fewer carbon atom than the starting amide, while the Hofmann rearrangement produces a primary amine with the same number of carbon atoms as the starting amide.
2. What are the reactants in the Hoffmann bromamide reaction?
The reactants in the Hoffmann bromamide reaction are a primary amide, bromine (Br2), and a strong base such as sodium hydroxide (NaOH) or potassium hydroxide (KOH).
3. Why is a strong base necessary in the Hoffmann bromamide reaction?
A strong base is necessary to deprotonate the intermediate species formed during the reaction and to neutralize the hydrogen bromide produced. It also helps in the formation of the isocyanate intermediate.
4. What is the first step in the Hoffmann bromamide reaction mechanism?
The first step in the Hoffmann bromamide reaction mechanism is the formation of an N-bromoamide. This occurs when bromine reacts with the amide in the presence of a base, replacing one of the amide's hydrogen atoms with a bromine atom.
5. How does the N-bromoamide form in the reaction?
The N-bromoamide forms when the base deprotonates the amide, creating a negatively charged nitrogen. This nitrogen then attacks the bromine molecule, forming an N-Br bond and releasing a bromide ion.
6. How does the Hoffmann bromamide reaction compare to reductive amination in amine synthesis?
The Hoffmann bromamide reaction and reductive amination are quite different approaches to amine synthesis:
7. Can the Hoffmann bromamide reaction be used with aromatic amides?
Yes, the Hoffmann bromamide reaction can be used with aromatic amides. However, the reaction may be slower compared to aliphatic amides due to the resonance stabilization of the aromatic amide. The product would be an aromatic amine (aniline derivative) with the carbonyl group removed.
8. What is the importance of the Hoffmann bromamide reaction in the history of organic chemistry?
The Hoffmann bromamide reaction is important in the history of organic chemistry for several reasons:
9. How does the Hoffmann bromamide reaction compare to the Schmidt reaction?
Both the Hoffmann bromamide reaction and the Schmidt reaction can convert carboxylic acids or their derivatives to amines with one fewer carbon atom. However:
10. How does the Hoffmann bromamide reaction differ from the Curtius rearrangement?
While both reactions can produce amines from carboxylic acid derivatives, they differ in several ways:
11. Can the Hoffmann bromamide reaction be reversed?
No, the Hoffmann bromamide reaction cannot be directly reversed. It involves the loss of a carbon atom as CO2, which makes it thermodynamically irreversible under normal conditions. To go from the amine back to the amide would require a different synthetic route.
12. What is an isocyanate intermediate and why is it important in this reaction?
An isocyanate intermediate is a highly reactive species with the general structure R-N=C=O. It's important in the Hoffmann bromamide reaction because it's the key intermediate that leads to the formation of the primary amine product.
13. How does the Hoffmann bromamide reaction exemplify green chemistry principles?
While the Hoffmann bromamide reaction has some green aspects, it also has significant drawbacks in terms of green chemistry:
14. How does the Hoffmann bromamide reaction demonstrate the concept of umpolung?
The Hoffmann bromamide reaction demonstrates umpolung (polarity inversion) in organic synthesis. In the original amide, the carbonyl carbon is electrophilic. However, in the isocyanate intermediate, the same carbon becomes nucleophilic, attacking water in the hydrolysis step. This inversion of polarity is a key feature of the reaction mechanism.
15. What is the Hoffmann bromamide reaction?
The Hoffmann bromamide reaction is an organic chemistry reaction that converts a primary amide to a primary amine with one fewer carbon atom. It involves the use of bromine and a base to degrade the amide, resulting in a primary amine with one less carbon than the original amide.
16. Who discovered the Hoffmann bromamide reaction?
The Hoffmann bromamide reaction was discovered by German chemist August Wilhelm von Hofmann in 1881. It's important to note that despite the similar names, this reaction is different from the Hofmann rearrangement.
17. What type of amines are produced by the Hoffmann bromamide reaction?
The Hoffmann bromamide reaction produces primary amines exclusively. These primary amines have one fewer carbon atom than the original amide.
18. Why does carbon dioxide form as a byproduct in the Hoffmann bromamide reaction?
Carbon dioxide forms as a byproduct because the hydrolysis of the isocyanate intermediate results in the cleavage of the C-N bond. The carbon that was originally part of the carbonyl group in the amide is released as CO2, which is why the resulting amine has one fewer carbon atom than the starting amide.
19. What is the overall stoichiometry of the Hoffmann bromamide reaction?
The overall stoichiometry of the Hoffmann bromamide reaction is:
20. How does the Hoffmann bromamide reaction compare to other methods of amine synthesis?
The Hoffmann bromamide reaction is unique in that it produces a primary amine with one fewer carbon atom than the starting material. This makes it useful for synthesizing certain amines that might be difficult to obtain through other methods. However, it's generally less commonly used than other amine synthesis methods due to its specific requirements and the loss of a carbon atom.
21. Can the Hoffmann bromamide reaction be used in the synthesis of amino acids?
Yes, the Hoffmann bromamide reaction can be used in the synthesis of certain amino acids. For example, it can be used to convert asparagine to α,β-diaminopropionic acid. However, it's not commonly used for this purpose due to the loss of a carbon atom and the potential for side reactions with other functional groups present in amino acids.
22. Can the Hoffmann bromamide reaction be used with secondary or tertiary amides?
No, the Hoffmann bromamide reaction is specific to primary amides. Secondary and tertiary amides lack the necessary N-H bonds required for the initial N-bromination step.
23. What are some limitations of the Hoffmann bromamide reaction?
Some limitations include: it only works with primary amides, it results in the loss of a carbon atom, it requires the use of potentially hazardous bromine, and it may not be compatible with certain functional groups that are sensitive to strong bases or oxidizing conditions.
24. How can you confirm that the Hoffmann bromamide reaction has occurred successfully?
You can confirm the success of the Hoffmann bromamide reaction through various analytical techniques. These include:
25. What is the role of the second equivalent of base in the reaction?
The second equivalent of base removes a proton from the N-bromoamide, forming an anion. This step is crucial for the subsequent rearrangement that leads to the isocyanate intermediate.
26. How does the isocyanate intermediate form in the Hoffmann bromamide reaction?
The isocyanate intermediate forms through a rearrangement of the N-bromoamide anion. The carbon-carbon bond between the carbonyl group and the R group migrates to form a bond with the nitrogen, displacing the bromine and creating the isocyanate structure.
27. What happens to the isocyanate intermediate in the presence of water?
In the presence of water, the isocyanate intermediate undergoes hydrolysis. This process involves the addition of water across the C=N double bond, ultimately leading to the formation of a primary amine and carbon dioxide.
28. Can you explain the stereochemistry of the Hoffmann bromamide reaction?
The Hoffmann bromamide reaction does not typically involve changes in stereochemistry. If the starting amide has a chiral center, it will be lost in the product amine due to the removal of the carbonyl carbon. Any chiral centers not adjacent to the amide group should remain unchanged.
29. How does temperature affect the Hoffmann bromamide reaction?
Temperature can affect the rate and yield of the Hoffmann bromamide reaction. Generally, higher temperatures increase the reaction rate but may also lead to side reactions. The reaction is typically carried out at room temperature or with mild heating to balance reactivity and selectivity.
30. What role does the solvent play in the Hoffmann bromamide reaction?
The solvent in the Hoffmann bromamide reaction should be able to dissolve both the organic amide and the inorganic base. Common choices include water or a mixture of water and an organic solvent like dioxane. The solvent also helps in heat distribution and can influence the reaction rate.
31. How does the electronic nature of the R group in RCONH2 affect the Hoffmann bromamide reaction?
The electronic nature of the R group can affect the reaction in several ways:
32. What are some industrial applications of the Hoffmann bromamide reaction?
While not as widely used as some other reactions, the Hoffmann bromamide reaction has found some industrial applications:
33. What safety precautions should be taken when performing the Hoffmann bromamide reaction?
When performing the Hoffmann bromamide reaction, several safety precautions should be taken:
34. What is the role of the bromide ion (Br-) produced in the reaction?
The bromide ion (Br-) produced in the reaction acts as a leaving group. It's displaced during the formation of the isocyanate intermediate. The bromide ion then combines with sodium or potassium from the base to form NaBr or KBr as a byproduct of the reaction.
35. Can the Hoffmann bromamide reaction be performed on a large scale?
While it's possible to perform the Hoffmann bromamide reaction on a larger scale, there are several challenges:
36. How does the presence of other functional groups in the molecule affect the Hoffmann bromamide reaction?
The presence of other functional groups can affect the Hoffmann bromamide reaction in several ways:
37. What is the significance of the isocyanate intermediate in the Hoffmann bromamide reaction?
The isocyanate intermediate is crucial in the Hoffmann bromamide reaction for several reasons:
38. Can the Hoffmann bromamide reaction be catalyzed?
The traditional Hoffmann bromamide reaction is not typically described as a catalytic process. However, some modified versions of the reaction have been developed that use catalysts:

Articles

Back to top