Problem 88 - A Complete Resource Book in Chemistry for JEE Main

Question

Identify the products of the following reaction, \(\mathrm{CH}_{3} \mathrm{C} \equiv \mathrm{CCH}_{2} \mathrm{CH}_{3} \stackrel{\text { (i) } \mathrm{O}_{3}}\) (ii) hydrolysis \(?+?\) (a) \(\mathrm{CH}_{3} \mathrm{COOH}+\mathrm{CO}_{2}\) (b) \(\mathrm{CH}_{3} \mathrm{COOH}+\mathrm{HOOC} \cdot \mathrm{CH}_{2} \mathrm{CH}_{3}\) (c) \(\mathrm{CH}_{3} \mathrm{CHO}+\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CHO}\) (d) \(\mathrm{CH}_{3} \mathrm{COOH}+\mathrm{CH}_{3} \mathrm{COCH}_{3}\)

Step-by-Step Solution

Answer

The products are option (b): \( \mathrm{CH}_{3} \mathrm{COOH} + \mathrm{HOOC} \cdot \mathrm{CH}_{2} \mathrm{CH}_{3} \).

Step 1: Understand the Reaction

The reaction involves the molecule \( \mathrm{CH}_{3} \mathrm{C} \equiv \mathrm{CCH}_{2} \mathrm{CH}_{3} \) undergoing ozonolysis followed by hydrolysis. Ozonolysis is a reaction where ozone breaks a double or triple bond, leading to the formation of carbonyl compounds.

Step 2: Consider Triple Bond Ozonolysis

In this specific reaction, the alkyne \( \mathrm{CH}_{3} \mathrm{C} \equiv \mathrm{CCH}_{2} \mathrm{CH}_{3} \) will be cleaved between the carbon-carbon triple bond. The two carbon atoms of the triple bond are converted into acid groups upon hydrolysis.

Step 3: Analyze Potential Products

Upon hydrolysis of the ozonide, the fragments will each gain an oxygen atom, being converted into carboxylic acids. For this given compound, two different acids are formed: acetic acid (\( \mathrm{CH}_{3} \mathrm{COOH} \)) and propionic acid (\( \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{COOH} \)).

Step 4: Match with Options

Compare the resulting compounds with the provided options:- (a) \( \mathrm{CH}_{3} \mathrm{COOH} + \mathrm{CO}_{2} \)- (b) \( \mathrm{CH}_{3} \mathrm{COOH} + \mathrm{HOOC} \cdot \mathrm{CH}_{2} \mathrm{CH}_{3} \)- (c) \( \mathrm{CH}_{3} \mathrm{CHO} + \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CHO} \)- (d) \( \mathrm{CH}_{3} \mathrm{COOH} + \mathrm{CH}_{3} \mathrm{COCH}_{3} \)The correct answer is (b) because it corresponds to the expected acetic acid and propionic acid products.

Key Concepts

Alkyne Reaction

Alkynes are hydrocarbons that contain at least one carbon-carbon triple bond \( \mathrm{C} \equiv \mathrm{C} \). This triple bond is highly reactive due to its electron-rich structure, which makes alkynes a target for various chemical reactions.

• Introduction of Ozone: When ozone \( \mathrm{O}_3 \) reacts with an alkyne, the process is known as ozonolysis. The triple bond is cleaved, effectively breaking the molecule into smaller fragments.
• Understanding Alkyne Ozonolysis: During ozonolysis of an alkyne, the triple bond is attacked by ozone, resulting in the formation of an ozonide intermediate. This eventually breaks into two carbonyl fragments upon further reactions.

This reaction is particularly useful in organic chemistry for converting alkynes into carbonyl-containing compounds such as carboxylic acids.

Hydrolysis

Hydrolysis is a chemical process that uses water to break down compounds. In organic chemistry, this often involves the transformation of an ozonide into more stable products rather than consuming water in a typical aqueous manner. Process of Hydrolysis in Ozonolysis:

• The unstable ozonide intermediate, formed during the ozonolysis of an alkyne, reacts with water to complete the hydrolysis process.
• This results in the conversion of the ozonide into carboxylic acids, as the cleavage of the triple bond turns into functional acid groups.

This step is critical for transforming the ozonide into useful organic compounds and understanding the fate of reaction products.

Carboxylic Acid Formation

Carboxylic acids are organic acids characterized by the \( \mathrm{COOH} \) group. Their formation from alkynes through ozonolysis followed by hydrolysis is a fascinating process involving distinct steps.Formation from Alkynes:

• Upon reaction with ozone, the triple bond of an alkyne is split. Each carbon originally involved in the triple bond is oxidized to produce a carboxylic acid group.
• In our context, this process converts the molecular fragments into specific acids: acetic acid \( \mathrm{CH}_3\mathrm{COOH} \) and propionic acid \( \mathrm{CH}_3\mathrm{CH}_2\mathrm{COOH} \).

This example demonstrates how alkyne ozonolysis leads to the formation of carboxylic acids, which have broad applications in both industrial and biological chemistry.