Problem 200 - A Complete Resource Book in Chemistry for JEE Main

Question

Which one of the following undergoes reaction with \(50 \%\) sodium hydroxide solution to give the corresponding alcohol and acid? \(\quad\) [2004] (a) phenol (b) benzaldehyde (c) butanal (d) benzoic acid

Step-by-Step Solution

Answer

None of the given options contain the necessary ester bond to undergo saponification into an alcohol and an acid.

Step 1: Identify the reaction

Sodium hydroxide ( NaOH) reacts with esters in a saponification reaction to produce an alcohol and a carboxylic acid. The question asks for a compound that, when reacted with 50% NaOH, yields an alcohol and an acid. This implies a chemical structure that can form both products after hydrolysis.

Step 2: Analyze each compound

- **Phenol (a):** Phenol is an alcohol with an aromatic ring and does not contain any ester functional group for hydrolysis to yield an additional alcohol and acid. - **Benzaldehyde (b):** It is an aldehyde and does not undergo saponification. - **Butanal (c):** Also an aldehyde lacking the ester group required for the reaction. - **Benzoic acid (d):** While it reacts with bases to form salts, it does not possess an ester group required for yielding an alcohol and an acid via saponification.

Step 3: Consider possible structural misunderstanding

In the case of (c) butanal, the problem may sometimes be misinterpreted. However, aldehydes like butanal do not form esters with the provided conditions without prior modification and cannot produce both an alcohol and an acid.

Step 4: Determine the correct answer

None of the given options include an ester group ready for direct hydrolysis to alcohol and acid. Typically, an ester would fit the description of decomposing into an alcohol and a carboxylic acid under the conditions described. This might imply a wrong or missing option, as none provided fit the ester criteria.

Key Concepts

Sodium Hydroxide

Sodium hydroxide, often called caustic soda, is a powerful base extensively used in chemical reactions. Its formula is NaOH and it appears as a white solid. In solution, it dissociates into sodium ions (Na⁺) and hydroxide ions (OH⁻). It's a highly reactive substance, especially when it interacts with compounds like esters. These interactions are vital in various industrial and laboratory processes.

• Reacts vigorously with acids to form salts and water
• Important in soap-making through saponification
• Used in the paper, textile, and detergent industries

Understanding sodium hydroxide's behavior in reactions helps in predicting product outcomes. Specifically, it plays a crucial role in ester hydrolysis, helping to break down esters into alcohols and carboxylic acids.

Alcohol Formation

Alcohol formation is a key outcome in the reaction of sodium hydroxide with esters. During saponification, an ester reacts with NaOH, and one of the products is an alcohol. This happens due to the hydrolysis of the ester bond.
The typical structure of an ester is RCOOR', where R and R' are hydrocarbon chains.

• The hydrolysis of the ester bond splits the molecule into an alcohol and a carboxylic acid.
• The R' group, which was initially bonded to the ester oxygen, becomes the alcohol group (R'OH).

This transformation is not just limited to simple lab settings but is fundamental in creating various alcohol-containing products found in everyday life.

Carboxylic Acid

A carboxylic acid forms alongside alcohol during ester hydrolysis reactions involving sodium hydroxide. This acid contains the functional group -COOH, which defines it.
When sodium hydroxide catalyzes the hydrolysis of an ester, the resulting carboxylic acid is essential in many biological and chemical processes.

• The R group from the ester remains with the carboxylic portion (RCOOH).
• Carboxylic acids react with bases to form salts and water, showing their integral role in neutralization reactions.

This component's formation is crucial in understanding many natural and industrial reactions. Carboxylic acids serve as building blocks for various chemical compounds, including polymers, and play a significant role in metabolism.

Ester Hydrolysis

Ester hydrolysis is a chemical process that breaks down an ester into an alcohol and a carboxylic acid. This reaction is central in the saponification process and is especially important in organic chemistry.
When an ester comes into contact with a strong base like sodium hydroxide, the reaction facilitates breaking the ester bond.

• This process involves nucleophilic attack by the hydroxide ion (OH⁻) on the carbon atom of the ester group.
• The resultant breakdown yields an alcohol from the ester group and a carboxylic acid from the acyl group.
• This reaction is characteristic of saponification, which is used in soap production.

Thus, ester hydrolysis through sodium hydroxide is not just an academic topic but has practical implications in producing everyday goods like soaps and in various industrial applications.