The main difference between Sandmeyer reaction and Gattermann reaction is that Sandmeyer reactions involve the synthesis of aryl halides from aryl diazonium salts in the presence of copper salts as a catalyst, whereas Gattermann reactions involve the formulation of the aromatic compound in the presence of a Lewis acid catalyst.
Both Sandmeyer reaction and Gattermann reactions are substitution types of reactions. These two common synthetic pathways are used to introduce various functional groups into the aromatic ring. Both reactions are named after the two scientists who discovered these reactions, Traugott Sandmeyer and Ludwig Gattermann, respectively.
Key Areas Covered
1. What is Sandmeyer Reaction
– Definition, Nature, Limitations
2. What is Gattermann Reaction
– Definition, Nature, Limitations
3. Similarities – Sandmeyer Reaction and Gattermann Reaction
– Outline of Common Features
4. Difference Between Sandmeyer Reaction and Gattermann Reaction
– Comparison of Key Differences
Key Terms
Sandmeyer Reaction, Gattermann Reaction
What is a Sandmeyer Reaction
Sandmeyer reactions are a type of organic substitution reaction. In this reaction, aryl halides are produced from aryl diazonium salts. Functional groups such as halides, hydroxyl, or even cyano groups may replace the diazonium group. The catalyst, copper(I)salt, helps to increase the rate of reaction in this reaction. This reaction is carried out in the presence of an acid such as hydrochloric acid or sulfuric acid.
Sandmeyer reaction follows a free radical mechanism. There are two steps in the process of this reaction. The nucleophile can be a halide anion, cyanide, water, etc. The transfer of a single electron from copper to diazonium is the starting point of the reaction. This results in the formation of a non-participating diazo radical as well as copper (II) halide. The diazo radical then releases a molecule of nitrogen gas to give aryl radical, which then reacts with the copper (ii) halide to restore the catalyst [copper (i) halide]. The final product of the reaction is aryl halide.
This reaction is very useful as a synthetic tool. The ability of the Sandmeyer reaction to include a wide range of functional groups into the aromatic ring makes it suitable for synthesizing various organic compounds. Moreover, this reaction is a mild reaction carried under mild conditions. In fact, it can be carried out in a variety of solvents, including water, ether, and alcohol.
Sandmeyer reactions also have some limitations. It is difficult to control the selectivity of the reaction. In some instances, multiple functional groups can form instead of the required product. The reaction can even be sensitive to moisture and air, resulting in reduced yields and side reactions.
What is Gattermann Reaction
Gattermann reactions are used for the synthesis of aromatic aldehydes from benzene derivatives. This chemical reaction utilizes a mixture of carbon monoxide and hydrogen chloride gases to selectively substitute a hydrogen atom on the aromatic ring of a benzene derivative with a formyl group. A Lewis acid, like copper (I) chloride, serves as the catalyst for this process. The intermediate that forms in this reaction is the “Gattermann intermediate.” At the end of the reaction, this transforms into the final product.
Moreover, the reaction conditions of the Gattermann reaction are relatively mild, and the reaction can be carried out at room temperature. Chloroform, dichloromethane, or carbon disulphide are the solvents that help to mix the reactants.
The ability to introduce the formyl group onto the aromatic ring of the benzene derivative in a single step is a useful feature in the synthesis of aromatic aldehydes, which are important intermediates.
Another advantage of the Gattermann reaction is the ability to introduce the formyl group to a wide range of benzene derivatives, including mono-, di- and tri-substituted benzene derivatives and heterocyclic aromatic compounds. This reaction can also help to introduce other functional groups onto the aromatic ring, like nitro, cyano, and halogen groups.
Apart from these advantages, the Gattermann reaction also has several limitations. One such limitation is the use of toxic and hazardous gases such as carbon monoxide and hydrogen chloride. Another limitation is the low yield certain derivatives produce.
Similarities Between Sandmeyer Reaction and Gattermann Reaction
- Sandmeyer reaction and Gattermann reactions are substitution reactions.
- Moreover, both reactions help in the introduction of functional groups into the aromatic ring.
Difference Between Sandmeyer Reaction and Gattermann Reaction
Definition
Sandmeyer reactions refer to a class of chemical reactions that involve aryl halides’ production by using aryl diazonium salts. On the other hand, Gattermann reactions are a type of chemical reaction that involves the synthesis of aromatic aldehydes from benzene derivatives.
Nature
Sandmeyer reactions involve the synthesis of aryl halides from aryl diazonium salts in the presence of copper salts as a catalyst. Meanwhile, Gattermann reactions involve the formulation of the aromatic compound in the presence of a Lewis acid catalyst.
Limitations
Limitations of Sandmeyer reactions include difficulty in controlling the reactions and sensitivity of the reaction to moisture and air, while the limitations of Gattermann reactions include the use of toxic and hazardous gases and the low yield obtained for certain derivatives.
Conclusion
In brief, both Sandmeyer reaction and Gattermann reactions are substitution types of reactions. The main difference between Sandmeyer reaction and Gattermann reaction is that Sandmeyer reactions involve the synthesis of aryl halides from aryl diazonium salts in the presence of copper salts as a catalyst, whereas Gattermann reactions involve the formulation of the aromatic compound in the presence of a Lewis acid catalyst.
Reference:
1. “Sandmeyer Reaction Mechanism.” Byju’s.
2. “Gattermann Reaction.” Protons Talk.
Image Courtesy:
1. “Sandmeyer reaction – overall” By CytochromeT – Own work (CC BY-SA 4.0) via Commons Wikimeda
2. “Gattermann II” (CC BY-SA 3.0) via Commons Wikimedia
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