Question

A new carbon-carbon bond formation is possible in 1\. Cannizzro reaction 2\. Feirdel-Craft's reaction 3\. Clemmensen reduction 4\. Reimer - Teimann reaction (a) 2,4 (b) 1,2 (c) 2,3 (d) \(1,2,4\)

Short answer

The answer is (a) 2,4.

Step-by-step solution

Understanding Carbon-Carbon Bond Formation

Carbon-carbon bond formation is a chemical reaction where two carbon atoms form a covalent bond, lengthening the carbon chain or creating a new organic framework. This process is essential in organic synthesis.

Analyzing Cannizzaro Reaction

The Cannizzaro reaction is a redox reaction that occurs in aldehydes without an alpha-hydrogen. It involves the disproportionation of the aldehyde into an alcohol and a carboxylic acid. It does not involve carbon-carbon bond formation.

Analyzing Friedel-Crafts Reaction

The Friedel-Crafts reaction includes alkylation or acylation, which are types of electrophilic aromatic substitution. These reactions result in the formation of carbon-carbon bonds by adding alkyl or acyl groups to an aromatic ring.

Analyzing Clemmensen Reduction

The Clemmensen reduction is a reaction where ketones or aldehydes are reduced to alkanes using zinc amalgam and hydrochloric acid. This process involves the removal of oxygen but does not create new carbon-carbon bonds.

Analyzing Reimer-Tiemann Reaction

The Reimer-Tiemann reaction specifically creates a formyl (–CHO) group on phenols, thereby forming a new carbon-carbon bond in the phenoxide ion. This reaction is utilized to synthesize ortho-formyl derivatives of phenols.

Identifying Possible Carbon-Carbon Bond Formation Reactions

From the analysis, the Friedel-Crafts reaction (2) and the Reimer-Tiemann reaction (4) both involve the formation of carbon-carbon bonds. These reactions can be used to extend carbon backbones or introduce new groups involving carbon.

Key concepts

Friedel-Crafts Reaction

The Friedel-Crafts reaction is a classic method in organic chemistry for carbon-carbon bond formation. It primarily involves two types of reactions: alkylation and acylation.

- **Alkylation:** This type adds an alkyl group to an aromatic ring. A common example is the reaction of an aromatic compound like benzene with an alkyl halide in the presence of a strong Lewis acid catalyst like AlCl₃. This reaction expands the aromatic ring system by introducing a new carbon-carbon bond.
- **Acylation:** In acylation, an acyl group is introduced to an aromatic ring. Like alkylation, it requires a Lewis acid. It usually involves the reaction of an acid chloride with an aromatic ring. This results in a new ketone group adjacent to the aromatic ring, forming a new carbon-carbon linkage.

Both processes are crucial for the synthesis of various chemicals in industrial and laboratory settings, especially those requiring an extended aromatic system.

Reimer-Tiemann Reaction

The Reimer-Tiemann reaction is a unique chemical reaction used to form carbon-carbon bonds by adding a formyl group to phenol to produce salicylaldehydes.

- **Mechanism:** The reaction typically involves chloroform (CHCl₃) and a strong base, like NaOH. Under these conditions, an electrophilic carbene is generated, which adds to the ortho position of the phenol. This results in a new formyl group (-CHO) on the phenol ring.
- **Application:** This reaction is essential in organic synthesis for introducing formyl groups into aromatic systems. It offers a robust strategy to generate aldehyde groups specifically on phenol derivatives, which are valuable intermediates in synthesizing other complex organic molecules.

The Reimer-Tiemann reaction is particularly valued for its selective formylation at the ortho position, making it a vital technique in synthetic organic chemistry.

Organic Synthesis

Organic synthesis is the field of chemistry focused on creating organic molecules through carefully planned chemical reactions. It allows chemists to construct new molecular frameworks or modify existing ones.

- **Importance of Carbon-Carbon Bonds:** Carbon-carbon bonds are fundamental in creating complex organic molecules. Reactions like Friedel-Crafts and Reimer-Tiemann enable the synthesis of new chemical entities by extending carbon frameworks.
- **Synthetic Strategies:** In organic synthesis, different strategies such as stepwise synthesis, where reactions are performed in a series, guide the construction of complex molecules. Multi-step synthesis might involve creating intermediates that are further manipulated to achieve the desired product.

Organic synthesis underpins countless applications in pharmaceuticals, material science, and biology, driving innovation by enabling the design and production of new compounds that solve real-world problems.