Problem 82 - A Complete Resource Book in Chemistry for JEE Main

Question

Which compound gives \(\mathrm{CO}_{2}\) with \(\mathrm{NaHCO}_{3} ?\) (a) hexanol (b) phenol + acetic acid (c) \(\mathrm{n}\)-butanol (d) acetic acid

Step-by-Step Solution

Answer

(b) phenol + acetic acid or (d) acetic acid

Step 1: Understand the Reaction

When a compound reacts with \( \mathrm{NaHCO}_3 \), it will release \( \mathrm{CO}_2 \) gas if it is an acid stronger than bicarbonate, such as carboxylic acids.

Step 2: Analyze Each Option

We need to analyze each option to see if it's an acid stronger than bicarbonate. \(\text{Hexanol}\) is an alcohol and not acidic, so it will not react. \(\text{Phenol + Acetic Acid}\) contains \(\text{acetic acid}\), a carboxylic acid, which can release \( \mathrm{CO}_2 \). \(\text{n-Butanol}\) is also an alcohol and not acidic. \(\text{Acetic acid}\) is a carboxylic acid, hence it will react.

Step 3: Identify the Correct Compound

Among the options, acetic acid is the only compound that can react with \( \mathrm{NaHCO}_3 \) to release \( \mathrm{CO}_2 \). Therefore, both option (b) and (d) involve acetic acid, which can produce \( \mathrm{CO}_2 \).

Key Concepts

Carboxylic Acids

Carboxylic acids are a specific class of organic compounds that are characterized by the presence of a carboxyl group (-COOH). This functional group consists of a carbon double-bonded to an oxygen and single-bonded to a hydroxyl group. Carboxylic acids are known for their acidic properties, which are significantly stronger than alcohols and phenols. This increased acidity is due to the electron-withdrawing nature of the carbonyl group that stabilizes the carboxylate ion formed after losing a proton. As a result, carboxylic acids can easily donate a proton in a solution, making them a versatile player in acid-base reactions. Common examples include acetic acid, formic acid, and citric acid.

Reaction with NaHCO3

The reaction between carboxylic acids and sodium bicarbonate (NaHCO\(_3\)) is a classic acid-base reaction. When a carboxylic acid comes into contact with NaHCO\(_3\), a chemical reaction takes place where the acidic proton of the carboxylic acid reacts with the bicarbonate ion. This reaction produces three main products: carbon dioxide (CO\(_2\)), water (H\(_2\)O), and a sodium salt of the carboxylic acid. This particular behavior is useful for distinguishing carboxylic acids from other organic compounds, such as alcohols or phenols, which do not effectively undergo this reaction with NaHCO\(_3\). The presence of effervescence, or bubbling, indicating the release of CO\(_2\), provides a visual confirmation of the reaction.

Carbon Dioxide Release

Carbon dioxide release is a crucial aspect of identifying and analyzing carboxylic acids. During the reaction of a carboxylic acid with NaHCO\(_3\), CO\(_2\) is released as a gas. This release can be recognized by observing the effervescence that occurs during the reaction. This visible production of gas is not only a key indicator of the reaction taking place but is also essential for the confirmation of the acid's reactive properties. The release of carbon dioxide is not just crucial for laboratory identification but also plays a significant role in industrial processes where such reactions are exploited for neutralization or chemical synthesis purposes. It's important to handle such reactions carefully as the generation of gas can lead to pressure build-up in closed systems.