Question

Which of the following compounds is least likely to give effervescence of CO$_2$ in presence of aq. NaHCO$_3$?

• A.
• B.
• C.
• D.

Hint:

In reactions with NaHCO\(_3\), look for acidic functional groups (like -COOH or -OH) that readily react to release CO\(_2\). Nitrogenous compounds without strong acidic groups generally do not react.

Answer 1

The Correct Option is D

To solve the problem of identifying which compound is least likely to give effervescence of CO₂ in the presence of aqueous NaHCO₃, we need to understand the reactivity of each compound with NaHCO₃. Typically, NaHCO₃ reacts with acids to release CO₂ gas. Therefore, compounds that are less acidic or not acidic at all will not liberate CO₂ when reacted with NaHCO₃.

Step-by-step Analysis:

1. Identify the acidic nature of each compound. Only acidic compounds will react with NaHCO₃ to produce CO₂.
   • A carboxylic acid group (COOH) or a phenol group is typically acidic.
   • Alcohols and ethers generally do not react with NaHCO₃ as they are not acidic enough.
2. Examine each option:
   • Option 1 presents a carboxylic acid group, which is acidic and will produce CO₂ with NaHCO₃.
   • Option 2 also features a carboxylic acid, with the same expected reactivity as Option 1.
   • Option 3 likely contains a phenol, which can be acidic under certain conditions and might produce CO₂ gas upon reaction.
   • Option 4 comprises an ether group, which is neither acidic nor likely to react with NaHCO₃.
3. Conclusion: The compound containing only an ether group (Option 4) is least likely to produce effervescence with NaHCO₃.

Correct Answer Explanation: The correct answer is the compound with the ether group (Option 4), as ethers do not have acidic protons to react with NaHCO₃ and generate CO₂ gas. Thus, it is the least likely to cause effervescence.

Answer 2

To determine which compound is least likely to give effervescence of CO₂ in the presence of aqueous NaHCO₃, we need to analyze the acidity of the compounds. This reaction is typically a test for carboxylic acids. Carboxylic acids react with sodium bicarbonate (NaHCO₃) to produce carbon dioxide (CO₂) gas, which causes effervescence. Let's evaluate each compound provided in the options:

1. Phenols and Alcohols: Phenols and alcohols do not react with NaHCO₃ to release CO₂ because they are weaker acids compared to carboxylic acids. Therefore, phenols and alcohols will not give effervescence with NaHCO₃.
2. Carboxylic Acids: Carboxylic acids will react with NaHCO₃, producing effervescence due to the release of CO₂.

The question asks for the compound least likely to give effervescence, indicating the compound that is not an acid or is a very weak acid.

Let's identify the correct structure:

The compound in the image (data-src-id="6809c3c2f6c672350d0d5aa0") represents a phenol group. Since phenols are weaker acids compared to carboxylic acids and do not readily give off CO₂ with NaHCO₃, this compound is the least likely to give effervescence.

Conclusion: The compound shown in the image above does not produce effervescence with NaHCO₃, making it the correct answer.