Question

Identify the name of reactions (A) - (D) given below (A) \(2 \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{I} \stackrel{\text { Na /ether }}{\longrightarrow} \mathrm{C}_{4} \mathrm{H}_{10}+2 \mathrm{NaI}\) (B) (C) \(\mathrm{R}_{2} \mathrm{CuLi} \stackrel{\mathrm{R}^{\prime} \mathrm{X}}{\longrightarrow} \mathrm{R}-\mathrm{R}\) (D) \(\mathrm{CH}_{3}-\mathrm{CO}-\mathrm{CH}_{3} \stackrel{\mathrm{Zn}-\mathrm{Hg} / \mathrm{HCl}}{\longrightarrow} \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{3}\) (a) (A) Ulmann reaction (B) Electrolytic cleavage (C) Grignard reaction (D) Wolff-kishner reduction (b) (A) Wurtz reaction (B) Kolbe's electrolysis (C) Corey-House synthesis (D) Clemmensen reaction (c) (A) Wurtz reaction (B) Decarboxylation (C) Frankland reaction (D) Clemmensen reduction (d) (A) Wurtz-Fittig reaction (B) Decarboxylative coupling (C) Corey-House synthesis (D) Clemmensen reduction

Short answer

Question: Identify the correct option describing the given reactions: (A) \(2 \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{I} \stackrel{\text { Na /ether}}{\longrightarrow} \mathrm{C}_{4} \mathrm{H}_{10} + 2 \mathrm{NaI}\) (C) \(\mathrm{R}_{2} \mathrm{CuLi} \stackrel{\mathrm{R}^{\prime} \mathrm{X}}{\longrightarrow} \mathrm{R}-\mathrm{R}\) (D) \(\mathrm{CH}_{3}-\mathrm{CO}-\mathrm{CH}_{3} \stackrel{\mathrm{Zn}-\mathrm{Hg} / \mathrm{HCl}}{\longrightarrow} \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{3}\) Options: (a) Reactions (A): Ulmann reaction, (C): Grignard reaction (b) Reactions (A): Wurtz reaction, (C): Corey-House Synthesis, (D): Clemmensen Reduction (c) Reactions (A): Wurtz reaction, (C): Frankland reaction, (D): Clemmensen Reduction (d) Reactions (A): Wurtz-Fittig reaction, (C): Corey-House Synthesis, (D): Clemmensen Reduction Answer: (b) Reactions (A): Wurtz reaction, (C): Corey-House Synthesis, (D): Clemmensen Reduction

Step-by-step solution

Analyzing Reaction (A)

For reaction (A), we have \(2 \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{I} \stackrel{\text { Na /ether}}{\longrightarrow} \mathrm{C}_{4} \mathrm{H}_{10}+2 \mathrm{NaI}\). This reaction involves using sodium metal in the presence of ether and results in the formation of a new carbon-carbon bond. This is a well-known reaction called the Wurtz reaction.

Analyzing Reaction (B)

As Reaction (B) is not given, we'll ignore this part.

Analyzing Reaction (C)

For reaction (C), we have \(\mathrm{R}_{2} \mathrm{CuLi} \stackrel{\mathrm{R}^{\prime} \mathrm{X}}{\longrightarrow} \mathrm{R}-\mathrm{R}\). In this reaction, an organocopper reagent formed from an organolithium compound reacts with an alkyl halide to produce a new carbon-carbon bond. This reaction is known as Corey-House Synthesis.

Analyzing Reaction (D)

For reaction (D), we have \(\mathrm{CH}_{3}-\mathrm{CO}-\mathrm{CH}_{3} \stackrel{\mathrm{Zn}-\mathrm{Hg} / \mathrm{HCl}}{\longrightarrow} \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{3}\). In this reaction, a ketone undergoes reduction in the presence of amalgamated zinc and hydrochloric acid, resulting in an alkane. This reaction is called the Clemmensen Reduction.

Identifying the Correct Option

Now, let's look at the options given: (a) This option incorrectly identifies reaction (A) as the Ulmann reaction and reaction (C) as the Grignard reaction. (b) This option correctly identifies all reactions: (A) as the Wurtz reaction, (C) as Corey-House Synthesis, and (D) as the Clemmensen Reaction. (c) This option incorrectly identifies reaction (C) as the Frankland reaction. (d) This option incorrectly identifies reaction (A) as the Wurtz-Fittig reaction. So, the correct answer is option (b).

Key concepts

Wurtz Reaction

The Wurtz Reaction is a classic method in organic chemistry used to form carbon-carbon bonds. It typically involves the coupling of two alkyl halides with sodium metal, resulting in the formation of a higher alkane. The reaction generally takes place in an inert solvent like dry ether.

Here's how it works in a step-by-step manner:

• An alkyl halide such as ethyl iodide ( \( \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{I} \) ) reacts with sodium (Na) metal.
• The sodium atoms donate electrons to the iodine, causing the alkyl groups to form radicals.
• The radicals then couple to form the final product, which is an alkane.

Wurtz Reaction is a useful tool for synthesizing symmetrical alkanes, especially when other methods are less effective. However, it is generally limited to primary alkyl halides to prevent unwanted side reactions.

Corey-House Synthesis

The Corey-House Synthesis is an important reaction for forming carbon-carbon bonds, particularly valuable for coupling complex organic molecules. It features the use of organocopper reagents, often formed from organolithium compounds.

This is how the process unfolds:

• First, an organolithium compound is treated with copper iodide to form a lithium dialkylcuprate complex, known as a Gilman reagent.
• Next, this complex reacts with an alkyl halide to form the coupled agglomerate, often producing very high yields.

The Corey-House Synthesis is widely celebrated for its ability to link two alkyl groups seamlessly. It's especially advantageous for synthesizing unsymmetrical molecules due to its high selectivity and efficiency.

Clemmensen Reduction

The Clemmensen Reduction is a widely-used method to convert ketones into alkanes. It employs amalgamated zinc and hydrochloric acid in its procedure. This method is particularly beneficial for compounds sensitive to acid.

Understanding Clemmensen Reduction involves these steps:

• A carbonyl compound like a ketone interacts with zinc amalgam in a strongly acidic medium.
• The carbonyl group (\(\mathrm{C=O}\)) is reduced to a methylene group (\(\mathrm{-CH_2-}\)).
• This conversion produces an alkane as the end product, fully eliminating the oxygen atom.

The Clemmensen Reduction is especially advantageous for aromatic ketones, serving as an alternative to other reductions where such conditions are necessary. It's a straightforward yet highly effective reaction, exemplifying the practical application of chemistry in transforming functional groups.