Problem 38 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following react with \(\mathrm{NaOH}\) to produce an acid and an alcohol? (a) \(\mathrm{CH}_{3} \mathrm{COOH}\) (b) HCHO (c) \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{COOH}\) (d) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{COOH}\)

Step-by-Step Solution

Answer

None of the given compounds react with NaOH to produce an acid and an alcohol.

Step 1: Understand the Reaction Conditions

To determine which compounds react with \(\text{NaOH}\) to produce an acid and an alcohol, recognize that this is a characteristic of esters in a saponification reaction.

Step 2: Identify Functional Groups

Inspect each compound to identify functional groups:(a) \(\text{CH}_3\text{COOH}\) - Carboxylic Acid(b) \(\text{HCHO}\) - Aldehyde(c) \(\text{C}_6\text{H}_5\text{COOH}\) - Carboxylic Acid(d) \(\text{CH}_3\text{CH}_2\text{COOH}\) - Carboxylic Acid

Step 3: Evaluate Each Option Against the Criteria

Check each compound to see if it contains an ester linkage, which is necessary to produce an acid and alcohol when reacted with \(\text{NaOH}\).(a) \(\text{CH}_3\text{COOH}\) and (c) \(\text{C}_6\text{H}_5\text{COOH}\) are acids, not esters.(b) \(\text{HCHO}\) is an aldehyde, not an ester.(d) \(\text{CH}_3\text{CH}_2\text{COOH}\) is also an acid.

Step 4: Determine the Correct Answer

Since none of the options (a), (b), (c), or (d) are esters, none of them will react with \(\text{NaOH}\) to produce both an acid and an alcohol.

Key Concepts

Ester Hydrolysis

Understanding ester hydrolysis is key to grasping the saponification process. Esters are organic compounds composed of an alcohol and an acid, where the hydrogen in the acid is replaced by an alkyl group. During ester hydrolysis, esters react with water in the presence of an acid or base catalyst (often \( ext{NaOH}\)). This reaction breaks down the ester into an alcohol and a carboxylic acid. This process is known as saponification when it's specifically used to make soap.
This reaction is characterized by a few essential components:

• An ester linkage, forming the base structure that is hydrolyzed.
• Water or hydroxide ions (like \( ext{OH}^-\) in \( ext{NaOH}\)), serving as the catalyst that facilitates the reaction.
• The release of an alcohol and carboxylic acid, the products of the hydrolysis.

This reaction is incredibly useful in various industries, not only for soap making but also in the production of fragrances and in the decomposition of biological substances.

Functional Groups

Functional groups are specific groupings of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. They play a pivotal role in determining the properties and reactivity of compounds.
In organic chemistry, several functional groups are out there, but for ester hydrolysis, the most relevant are:

• Carboxylic Acids: Defined by the \(\text{-COOH}\) group, these acids are not characterized by alcohol production when extending their reactions, unlike esters.
• Aldehydes: Characterized by the \(\text{-CHO}\) group, aldehydes contribute to distinct organic reactions but are not involved in forming esters.
• Esters: Featuring an \(\text{-COO-}\) linkage, essential for yielding an acid and an alcohol during hydrolysis.

Recognizing these groups allows chemists to predict how compounds will react under various conditions, a key skill in organic synthesis and analysis.

Chemical Reaction Conditions

Reactions involving esters often require certain conditions to proceed, particularly ester hydrolysis.
The key conditions for this reaction include:

• Presence of a Catalyst: Usually an acid or a base like \(\text{NaOH}\) is needed to accelerate the hydrolysis by breaking the ester linkage.
• Temperature: Heat is often applied to speed up the reaction, although too much can cause unwanted side reactions.
• Solvent Systems: Water or alcohol as a solvent is typical, providing the necessary medium for ions to interact.

Through understanding and manipulating these conditions, chemists can efficiently carry out ester hydrolysis. This is an important technique in both laboratory research and industrial applications where fine control over reactions is necessary.