Problem 6 - A Complete Resource Book in Chemistry for JEE Main

Question

Acetylene reacts with acetic acid in presence of \(\mathrm{Hg}^{+}\) ions at room temperature to give (a) ethyl acetate (b) acetaldehyde (c) vinyl acetate (d) methyl acetate

Step-by-Step Solution

Answer

The correct answer is (c) vinyl acetate.

Step 1: Identify the Reactants and Conditions

The reactants are acetylene ( C2H2 ) and acetic acid (CH3COOH) under the presence of mercury (Hg^+) ions at room temperature.

Step 2: Recognize the Reaction Type

This reaction is an example of a hydration reaction where the alkyne (acetylene) is hydrated in the presence of an acid catalyst.

Step 3: Determine the Product Formation

In this reaction, acetylene reacts with acetic acid in the presence of mercury ions to form vinyl acetate. This is because the acetylene adds across the carboxyl group of acetic acid.

Step 4: Confirm the Correct Option

The correct answer to the reaction between acetylene and acetic acid in the presence of Hg^+ ions is the formation of vinyl acetate. Thus, option (c) vinyl acetate is the correct answer.

Key Concepts

Acetylene Reactions

Acetylene, also known as ethyne, is a simple alkyne with the chemical formula \(C_2H_2\). It's a colorless gas with a distinct odor and is highly flammable. In organic chemistry, acetylene serves as a versatile building block due to its triple bond, which allows it to participate in various reactions. One of the most notable reactions involving acetylene is its ability to undergo hydration, producing different organic compounds.

• Acetylene's triple bond is composed of one sigma bond and two pi bonds, which makes it highly reactive.
• Its reactions typically involve addition across the triple bond, converting it into more stable single or double bonds.
• Common reactions include polymerization, oxidation, and formation of various chemical compounds.

The presence of catalytic agents such as metals and acids can influence the reaction pathway of acetylene, leading to the production of desired organic compounds like vinyl acetate.

Vinyl Acetate Formation

Vinyl acetate is a type of ester with an important role in the production of polyvinyl acetate and other polymers. It forms through specific reactions involving acetylene. In particular, when acetylene reacts with acetic acid in the presence of a mercury ion catalyst, vinyl acetate is produced. This reaction is an excellent example of how the use of catalysts can guide the formation of valuable compounds.

• The process involves the addition of acetylene to the carboxyl group of acetic acid.
• The presence of \(Hg^+\) ions facilitates the reaction by stabilizing the transition state.
• This catalysis is crucial in industrial settings, ensuring efficient and economical production processes.

Vinyl acetate is crucial in the manufacture of adhesives, paints, and plastics, showcasing its wide application in everyday products. The controlled reaction conditions ensure high yields and purity of the product.

Hydration Reaction

A hydration reaction in organic chemistry is where a water molecule is added to a compound. This type of reaction often occurs in alkynes and alkenes, transforming them into alcohols or other derivatives. In the case of acetylene, the hydration process is slightly modified. Instead of simple hydration, it's an acid-catalyzed process, often involving organic acids.

• The typical hydration reactions for alkynes result in the formation of an enol, which quickly tautomerizes to form a more stable keto compound.
• In the presence of catalysts like mercury ions, hydration can lead to alternative products, such as esters, as seen in vinyl acetate formation.
• Understanding the conditions and catalysts involved helps manipulate the product outcome, allowing chemists to direct reactions as needed for industrial applications.

For students, recognizing the mechanisms of hydration reactions is key to mastering the synthesis and transformation of organic molecules. It's a fundamental concept that underpins many processes in organic chemistry.