Grob fragmentation

What is Grob fragmentation?

Grob fragmentation is a chemical reaction that involves the cleavage of a carbon-carbon bond in a molecule, resulting in the formation of two smaller fragments. This reaction was first reported by Fritz Grob and his colleagues in the 1950s, and has since become a widely used synthetic method in the field of chemistry..

The Grob fragmentation reaction typically involves the use of a nucleophile, such as a carbanion or a carbonate anion, which attacks the carbon atom of the carbon-carbon bond, breaking the bond and forming two smaller fragments. The reaction is typically carried out in the presence of a solvent, such as dimethylformamide or tetrahydrofuran..

One of the key benefits of the Grob fragmentation reaction is that it allows for the synthesis of a wide range of products with a high degree of regioselectivity and stereoselectivity. This means that the reaction can be used to produce products with specific arrangements of substituents on the resulting fragments..

The Grob fragmentation reaction has a wide range of applications in the synthesis of a variety of compounds, including pharmaceuticals, dyes, and materials.

Summary

The Grob fragmentation reaction is an important tool in the synthesis of a wide range of products and has a wide range of applications in the field of chemistry..

Example

The Grob fragmentation is a reaction used to convert a carbonyl compound into a more complex molecule. An example of the Grob fragmentation is the reaction between ethyl 4-nitrocinnamate and sodium hydride:

Ethyl 4-nitrocinnamate is treated with a base, such as sodium hydride, to form an enolate ion..

The enolate ion is then reacted with a halogenated reagent such as chlorine to form an intermediate called the Grob intermediate..

The intermediate is then subjected to a ring-opening reaction, where the halogenated reagent is eliminated to form a new carbon-carbon bond, and two new fragments..

The newly formed fragments are typically a carbanion and a halogenated compound..

Mechanism of reaction

The Grob fragmentation is a reaction used to convert a carbonyl compound into a more complex molecule. The mechanism of the reaction can be broken down into the following steps:

The carbonyl compound is treated with a base, such as sodium hydride, to form an enolate ion..

The enolate ion is then reacted with a halogenated reagent, such as a halogenated carbonyl compound, to form an intermediate called the Grob intermediate..

The intermediate is then subjected to a ring-opening reaction, where the halogenated reagent is eliminated to form a new carbon-carbon bond, and two new fragments..

The newly formed fragments are typically a carbanion and a halogenated compound..

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