What is the Schmidt Reaction mechanism and products
What is Schmidt Reaction?
The Schmidt reaction is an important name reaction of organic chemistry. In this reaction azide (conjugate base of hydrazoic acid) reacts with a carbonyl derivative (such as carboxylic acid, aldehyde, ketone) under acidic conditions to give amine or amides with release of nitrogen. It is a rearrangement reaction. That’s why it is also known as Schmidt rearrangement reaction. This reaction is very closely reacted to another name reaction called Curtius rearrangement.
When Schmidt reaction takes place with carboxylic acid, it gives amine while when it takes place with ketone, it gives amides. Although in Schmidt reactions of both carboxylic acid and ketone, hydrazoic acid is used and nitrogen gets released.
Schmidt Reaction with Carboxylic Acid –
Carboxylic acid + Hydrazoic acid 🡪 Primary amine + Carbon dioxide + Nitrogen
Reaction –
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Schmidt Reaction with Ketone –
Ketone + Hydrazoic acid 🡪 Amide + Nitrogen
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Schmidt reaction is named after Karl Friedrich Schmidt (1887 - 1971). As Karl Friedrich Schmidt 1st reported the reaction by converting benzophenone and hydrazoic acid to benzanilide in 1924. Although Schmidt reaction for carboxylic acid was not reported until 1991.
Mechanism of Schmidt Reaction
First, we are describing here the mechanism of Schmidt reaction with carboxylic acids. Mechanism of this reaction can be understood by following 5 steps –
Step 1. Formation of Acylium Ion – Schmidt reaction with carboxylic acid starts with formation of acylium ion. It is formed by protonation of carboxylic acid with removal of water molecule. Reaction is given below –
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Step 2. Acylium Ion Reaction with Hydrazoic Acid – Acylium ion reacts with hydrazoic acid and forms protonated azido ketone. Reaction is given below –
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Step 3. Rearrangement of Azido Ketone – Now azido ketone undergoes rearrangement with alkyl group (R) migrating over the C-N bond and with removal of nitrogen gas. Rearrangement of azido ketone forms protonated isocyanate. Reaction is given below –
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Step 4. Formation of Carbamate – Water molecule attacks on the protonated isocyanate and forms carbamate. Reaction is given below –
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Step 5. Deprotonation of Carbamate and Formation of Amine – Now carbamate undergoes deprotonation and forms carbon dioxide and amine. Reaction is given below –
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Mechanism of Schmidt Reaction of Ketones
Mechanism of Schmidt reaction of ketone can be understood by following steps through Beckmann rearrangement –
Step 1. Activation of Carbonyl Group of Ketone – The carbonyl group of ketone is activated by protonation for nucleophilic addition by the azide. Reaction is given below -
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Step 2. Formation of Azidohydrin – Azidohydrin is formed by nucleophilic addition of nucleophile N3- at activated carbon of carbonyl group of ketone. Reaction is given below –
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Step 3. Formation of Diazoiminium – Azidohydrin loses water molecules in an elimination reaction to give diazoiminium. Reaction is given below –
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Step 4. Formation of Nitrilium Intermediate – One of the alkyl (or aryl) groups migrates from carbon of diazoiminium to nitrogen with loss of nitrogen to give a nitrilium intermediate as in the Beckmann rearrangement. Reaction is given below –
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Step 5. Formation of Imidic Acid – Now a water molecule attacks on nitrilium intermediate and converts it into protonated imidic acid.
Step 6. Formation of Amide – Now imidic acid undergoes loss of proton to arrive at its tautomer of the final amide. Reactions of step 5 and 6 are given below together –
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In an alternative mechanism, reaction may occur in a similar manner as Baeyer – Villiger reaction to give protonated amide.
Schmidt Reaction and Curtius Rearrangement
Schmidt reaction and Curtius rearrangement are closely related reactions. In Curtius rearrangement reaction acyl azide is produced by the reaction of acid chloride with sodium azide and the acid chloride is formed by the reaction of carboxylic acid with SOCl2 . While in Schmidt reaction acyl azide is produced by reaction of the carboxylic acid with hydrazoic acid as discussed under the section – What is Schmidt Reaction?
For your better understanding we are giving here a brief explanation of Curtius rearrangement.
Curtius Rearrangement - Theodor Curtius was doing various experiments with acyl azides. During these experiments he discovered that on thermal decomposition of an acyl azide, it gives isocyanate with loss of nitrogen gas. The isocyanate on reaction with alcohols gives carbamate and with water and amines gives primary amine and urea derivatives respectively. The reaction is given below –
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Thus, Curtius rearrangement reaction is thermal decomposition of carboxylic azides (such as acyl azide) to give isocyanate. In Curtius rearrangement acyl azide can be prepared by either reaction of acid chlorides or acid anhydrides with sodium azide or trimethyl azide or direct reaction of carboxylic acid with diphenylphosphoryl azide. Reactions are given below –
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This ends our coverage on the topic “Schmidt Reaction”. We hope you enjoyed learning and were able to grasp the concepts. We hope after reading this article you will be able to solve problems based on the topic and will not get confused between Curtius Rearrangement and Schmidt Reaction. If you are looking for solutions to NCERT Textbook problems based on this topic, then log on to Vedantu website or download Vedantu Learning App. By doing so, you will be able to access free PDFs of NCERT Solutions as well as Revision notes, Mock Tests and much more.
FAQs on Schmidt Reaction in Organic Chemistry
1. What is the Schmidt reaction in organic chemistry?
The Schmidt reaction is an organic rearrangement in which carboxylic acids, ketones, or aldehydes react with hydrazoic acid (HN3) under acidic conditions to form amines or amides with nitrogen insertion and rearrangement. It is commonly used to convert:
- Carboxylic acids → primary amines (with loss of CO2)
- Ketones → amides
- Aldehydes → nitriles (in many cases)
2. What is the general reaction mechanism of the Schmidt reaction?
The Schmidt reaction mechanism involves nucleophilic attack by azide followed by rearrangement and nitrogen loss. The key steps are:
- Protonation of the carbonyl group under strong acid (usually H2SO4).
- Attack by HN3 to form an acyl azide or related intermediate.
- Rearrangement with migration of an alkyl or aryl group.
- Loss of N2(g), forming an isocyanate or nitrilium ion.
- Hydrolysis to give the final amine or amide.
3. What are the products of the Schmidt reaction for carboxylic acids?
When a carboxylic acid undergoes the Schmidt reaction, the main product is a primary amine with one fewer carbon atom. For example:
- R–COOH + HN3 → R–NH2 + CO2(g) + N2(g) (acidic conditions)
4. What happens when ketones undergo the Schmidt reaction?
When a ketone undergoes the Schmidt reaction, it forms a substituted amide through rearrangement. The general transformation is:
- R–CO–R′ + HN3 → R–CONH–R′ (acidic conditions)
5. How is the Schmidt reaction different from the Curtius rearrangement?
The main difference is that the Schmidt reaction uses hydrazoic acid (HN3) directly with carbonyl compounds, while the Curtius rearrangement starts from an isolated acyl azide. Key distinctions include:
- Schmidt reaction: Carboxylic acid + HN3 under strong acid.
- Curtius rearrangement: Acyl azide heated to form an isocyanate.
- Both produce isocyanates and release N2(g).
6. Why is hydrazoic acid used in the Schmidt reaction?
Hydrazoic acid (HN3) is used because it provides the azide (N3−) group needed for nitrogen insertion and rearrangement. Its role includes:
- Acting as a nucleophile toward protonated carbonyl groups.
- Forming acyl azide intermediates.
- Releasing stable N2(g), which drives the reaction forward.
7. What is the role of acid in the Schmidt reaction?
A strong acid such as H2SO4 is required to protonate the carbonyl group and activate it toward azide attack. The acid:
- Increases electrophilicity of the carbonyl carbon.
- Facilitates formation of the rearranged intermediate.
- Promotes hydrolysis of the isocyanate to amine or amide.
8. Can you give an example of the Schmidt reaction with a balanced equation?
An example of the Schmidt reaction is the conversion of acetic acid to methylamine under acidic conditions. The simplified balanced equation is:
- CH3COOH + HN3 → CH3NH2 + CO2(g) + N2(g)
9. What is the difference between the Schmidt reaction and the Beckmann rearrangement?
The key difference is that the Schmidt reaction uses carbonyl compounds and azide, while the Beckmann rearrangement converts oximes into amides. Specifically:
- Schmidt: Ketone + HN3 → Amide + N2(g).
- Beckmann: Oxime + acid → Amide (no azide involved).
- Both involve group migration to nitrogen.
10. What are the common applications of the Schmidt reaction?
The Schmidt reaction is mainly used in organic synthesis to prepare amines and amides from carbonyl compounds. Its applications include:
- Conversion of carboxylic acids to primary amines.
- Synthesis of substituted amides from ketones.
- Preparation of nitrogen-containing pharmaceuticals and intermediates.
