Question

Which of the following rcactions takes place in the presence of anhydrous aluminium chloride? (1) Fricdcl Crafts (2) Cannizzaro's (3) Kolbc's (4) IIofmann's

Short answer

Friedel-Crafts reaction

Step-by-step solution

- Analyze Reaction Types

Review each of the given reaction types to understand their requirements and conditions.

- Determine Conditions for Each Reaction

Identify the conditions required for each reaction. For Friedel-Crafts reaction, anhydrous aluminium chloride is used as a catalyst. The other reactions (Cannizzaro, Kolbe, Hofmann) do not use anhydrous aluminium chloride.

- Verify with Reaction Mechanism

Cross-check with the mechanism of the Friedel-Crafts reaction to confirm that anhydrous aluminium chloride is indeed used to facilitate the reaction, typically for alkylation or acylation of aromatic compounds.

- Conclusion

Confirm that the only reaction from the list that uses anhydrous aluminium chloride as a catalyst is the Friedel-Crafts reaction.

Key concepts

anhydrous aluminium chloride

Anhydrous aluminium chloride, often abbreviated as AlCl3, plays a crucial role in organic chemistry reactions, particularly in Friedel-Crafts reactions. This substance is effective as a catalyst due to its ability to accept electron pairs, making it a Lewis acid. AlCl3 is used in reactions where polar and non-polar compounds don't mix easily.
In the Friedel-Crafts reaction, it helps in generating a carbocation or acylium ion from haloalkanes or acyl chlorides. These highly reactive intermediates are essential for substituting aromatic rings.
Using anhydrous AlCl3 is important as the presence of water could deactivate it by converting it to aluminium hydroxide, rendering it ineffective.

reaction mechanisms

Understanding reaction mechanisms is essential to grasp how chemical reactions proceed step-by-step. In the context of the Friedel-Crafts reaction, the mechanism involves three key steps:
1. Formation of the Electrophile: AlCl3 interacts with alkyl halide or acyl chloride to form a carbocation or acylium ion.
2. Formation of the Intermediate: The generated electrophile attacks the aromatic ring, forming a positively charged intermediate.
3. Restoration of Aromaticity: The intermediate loses a proton to regain aromaticity, completing the substitution.
This detailed mechanism illustrates how catalysts like AlCl3 facilitate the reaction by stabilizing intermediates, ensuring the reaction proceeds smoothly and efficiently.

organic chemistry

Organic chemistry is the study of carbon-containing compounds, including their structures, properties, and reactions. One of the fascinating areas in this field is the study of aromatic compounds, which are known for their stability and unique chemical behavior.
Reactions like the Friedel-Crafts alkylation and acylation are fundamental in modifying aromatic compounds. These reactions expand the toolbox of organic chemists, allowing them to synthesize a wide range of complex molecules used in pharmaceuticals, agrochemicals, and materials science.
The use of catalysts like anhydrous aluminium chloride in organic chemistry showcases how manipulation at the molecular level can lead to significant advancements in chemical synthesis and industrial applications.