Friedel Crafts Alkylation and Acylation Reaction Mechanism - Electrophilic Aromatic Substitution

TL;DR

The Friedel-Crafts Alkylation reaction involves replacing a hydrogen with an alkyl group on a benzene ring using an alkyl halide and a Lewis acid catalyst, while the Friedel-Crafts Isolation reaction involves the addition of an acid chloride followed by reduction to obtain the desired alkane product.

Transcript

in this video we're going to go over the frito crafts alkylation reaction and also the isolation reaction so let's start with benzene and the freedom crafts alkylation reaction we are going to add an alkyl halide let's use a tert-butyl chloride and we need a lewis acid catalyst we're going to use the aluminum chloride for this particular reaction n... Read More

Key Insights

• 😋 The Friedel-Crafts Alkylation reaction involves the replacement of a hydrogen on a benzene ring with an alkyl group using an alkyl halide and a Lewis acid catalyst.
• 🥺 Carbocation rearrangements can occur in the reaction, leading to the formation of different alkylated products.
• 😋 The presence of strongly deactivating groups on the benzene ring prevents the Friedel-Crafts Alkylation reaction from occurring.

Questions & Answers

Q: What is the main concept behind the Friedel-Crafts Alkylation reaction?

The main concept behind the Friedel-Crafts Alkylation reaction is the replacement of a hydrogen on a benzene ring with an alkyl group, achieved by reacting an alkyl halide with a Lewis acid catalyst, such as aluminum chloride.

Q: How does the Lewis acid catalyst assist in the formation of a carbocation intermediate?

The Lewis acid catalyst, such as aluminum chloride, has an empty p orbital that can accept a pair of electrons from the chlorine atom of the alkyl halide. This leads to the formation of a carbocation intermediate, which is necessary for the alkylation reaction to occur.

Q: Why does the Friedel-Crafts Alkylation reaction fail when strongly deactivating groups are present on the benzene ring?

Strongly deactivating groups, such as nitro groups, withdraw electron density from the benzene ring, resulting in a positive charge on the ring. This makes the ring less nucleophilic and less likely to react with the positively charged carbocation intermediate, leading to no reaction.

Q: How can carbocation rearrangements occur in the Friedel-Crafts Alkylation reaction?

Carbocation rearrangements can occur in the Friedel-Crafts Alkylation reaction when the initial carbocation formed is unstable. In such cases, a rearrangement of the carbocation can take place, resulting in the formation of a more stable carbocation, which is then attacked by the benzene ring.

Summary & Key Takeaways

• The Friedel-Crafts Alkylation reaction involves replacing a hydrogen on a benzene ring with an alkyl group using an alkyl halide and a Lewis acid catalyst, such as aluminum chloride.

• The reaction proceeds through the formation of a carbocation intermediate, which is attacked by the benzene ring and then deprotonated to form the alkylated product.

• The Friedel-Crafts Isolation reaction involves the addition of an acid chloride to a benzene ring, followed by reduction to achieve the desired alkane product.