The key difference between Sandmeyer reaction and Gattermann reaction is that Sandmeyer reaction refers to the synthesis of aryl halides from aryl diazonium salts in the presence of copper salts as a catalyst whereas Gattermann reaction refers to the formylation of aromatic compounds in the presence of a Lewis acid catalyst.
Both Sandmeyer reaction and Gattermann reaction are specific types of substitution reactions, named after the scientists who discovered the reaction. Accordingly, the name “Sandmeyer” originates from Traugott Sandmeyer, while the name “Gattermann” originates from Ludwig Gattermann.
CONTENTS
1. Overview and Key Difference
2. What is Sandmeyer Reaction
3. What is Gattermann Reaction
4. Side by Side Comparison – Sandmeyer Reaction vs Gattermann Reaction in Tabular Form
5. Summary
What is Sandmeyer Reaction?
Sandmeyer reaction is a type of organic substitution reaction in which we can synthesize aryl halides from aryl diazonium salts. The catalyst we use in this reaction is copper(I) salts. In addition, this reaction falls under the category of radical-nucleophilic aromatic substitution. Moreover, it is very useful in halogenation, cyanation, trifluoromethylation and hydroxylation of benzene.
Further, this reaction mechanism begins with a single electron transfer that occurs from copper to diazonium. It forms a neutral diazo radical and copper(II) halide. Then the diazo radical releases a nitrogen gas molecule, forming an aryl radical. The aryl radical then reacts with copper(II) halide to regenerate copper(I) halide. Therefore, we can get the final product: an aryl halide.
What is Gattermann Reaction?
Gattermann reaction is an organic substitution reaction in which we can formylate aromatic compounds. We can do this in the presence of Lewis ad catalysts. Moreover, the formylation is done using a mixture of HCN (hydrogen cyanide) and HCl (hydrochloric acid). The Lewis acid catalyst we use mostly is AlCl3. Furthermore, for simplification, we can replace the HCN/HCl mixture by zinc cyanide. Thus, this method becomes safer as well because zinc cyanide is not that toxic like HCN.
Step 1:
Step 2:
Furthermore, it is important to note that Gattermann reaction is important in introducing aldehyde groups to the benzene ring.
What is the Difference Between Sandmeyer Reaction and Gattermann Reaction?
Sandmeyer reaction is a type of organic substitution reaction in which we can synthesize aryl halides from aryl diazonium salts while Gattermann reaction is an organic substitution reaction in which we can formylate aromatic compounds. So, the key difference between Sandmeyer reaction and Gattermann reaction is that the Sandmeyer reaction refers to the synthesis of aryl halides from aryl diazonium salts in the presence of copper salts as a catalyst, whereas Gattermann reaction refers to the formylation of aromatic compounds in the presence of a Lewis acid catalyst.
Moreover, there is a difference between Sandmeyer reaction and Gattermann reaction based on the usage. Sandmeyer reaction is useful in halogenation, cyanation, trifluoromethylation and hydroxylation of benzene, while the Gattermann reaction is important in introducing aldehyde groups to the benzene ring.
Summary – Sandmeyer Reaction vs Gattermann Reaction
Sandmeyer reaction is a type of organic substitution reaction in which we can synthesize aryl halides from aryl diazonium salts while Gattermann reaction is an organic substitution reaction in which we can formylate aromatic compounds. So, the key difference between Sandmeyer reaction and Gattermann reaction is that Sandmeyer reaction refers to the synthesis of aryl halides from aryl diazonium salts in the presence of copper salts as a catalyst, whereas Gattermann reaction refers to the formylation of aromatic compounds in the presence of a Lewis acid catalyst.
Reference:
1. “Sandmeyer Reaction.” Name-Reaction.com, Available here.
Image Courtesy:
1. “Sandmeyerbromination” By Alsosaid1987 – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Gattermann I” (CC BY-SA 3.0) via Commons Wikimedia
3. “Gattermann II” (CC BY-SA 3.0) via Commons Wikimedia