Question

The compounds that produce CO$_2$ with aqueous NaHCO$_3$ solution are:

• A. A and C Only
• B. A, B, and E Only
• C. A, C, and D Only
• D. A and B Only

Hint:

Carboxylic acids and other sufficiently acidic functional groups react with bicarbonates to release carbon dioxide, a useful reaction for identifying certain organic functional groups.

Answer 1

The Correct Option is C

Aqueous sodium bicarbonate ($ NaHCO_3 $) solution is a weak base. Carboxylic acids react with $ NaHCO_3 $ to produce carbon dioxide ($ CO_2 $). Phenols are generally weaker acids than carboxylic acids and do not react with $ NaHCO_3 $ unless they are substituted with strong electron-withdrawing groups.

A. Benzoic acid ($ C_6H_5COOH $): Carboxylic acids react with $ NaHCO_3 $ to produce $ CO_2 $.
This compound produces $ CO_2 $.

B. Phenol ($ C_6H_5OH $): Phenols are generally weaker acids than carbonic acid and do not react with $ NaHCO_3 $.
This compound does NOT produce $ CO_2 $.

C. Picric acid (2,4,6-trinitrophenol): This is a strongly acidic phenol due to the presence of three nitro groups. It can react with $ NaHCO_3 $ to produce $ CO_2 $.
This compound produces $ CO_2 $.

D. Cyclohexanecarboxylic acid ($ C_6H_{11}COOH $): Carboxylic acids react with $ NaHCO_3 $ to produce $ CO_2 $.
This compound produces $ CO_2 $.

E. 4-Methoxyphenol: It is a very weak phenol and does not react with $ NaHCO_3 $, even slightly.
This compound does NOT produce $ CO_2 $.

Therefore, the compounds that produce $ CO_2 $ when reacted with aqueous $ NaHCO_3 $ are A, C, and D.

Final Answer:
The final answer is $ (3)\ A,\ C\ \text{and}\ D\ \text{only} $.

Answer 2

Step 1: Understand the question.
We are asked to identify which compounds among the given options produce CO₂ when treated with aqueous NaHCO₃ solution.

Step 2: Recall the chemical principle.
Only acidic compounds strong enough to react with sodium bicarbonate (NaHCO₃) will produce carbon dioxide (CO₂).
The reaction occurs when the acid has a pKa lower than that of carbonic acid (≈ 6.3).
Hence, carboxylic acids and strongly acidic phenols (with electron-withdrawing groups) can react with NaHCO₃ to evolve CO₂.

Step 3: Analyze each compound.
(A) Benzoic acid (C₆H₅COOH)
Benzoic acid is a carboxylic acid (pKa ≈ 4.2), which is sufficiently acidic to react with NaHCO₃ and liberate CO₂.
✅ Reacts with NaHCO₃.

(B) Phenol (C₆H₅OH)
Phenol is a weak acid (pKa ≈ 10) and does not react with NaHCO₃ since it is less acidic than carbonic acid.
❌ Does not react.

(C) 2,4,6-Trinitrophenol (picric acid)
Due to the presence of three strong electron-withdrawing NO₂ groups, phenolic acidity increases greatly (pKa ≈ 0.3), making it stronger than carbonic acid. It therefore reacts with NaHCO₃ and releases CO₂.
✅ Reacts with NaHCO₃.

(D) Cyclohexanecarboxylic acid
It is an aliphatic carboxylic acid (pKa ≈ 4.8), sufficiently acidic to react with NaHCO₃ and release CO₂.
✅ Reacts with NaHCO₃.

(E) p-Methoxyphenol
The methoxy group (–OCH₃) is an electron-donating group, which decreases the acidity of the phenol (pKa ≈ 10.2). It does not react with NaHCO₃.
❌ Does not react.

Step 4: Conclusion.
The compounds that produce CO₂ with aqueous NaHCO₃ are those that are sufficiently acidic:
A, C, and D only.

Final Answer:
A, C, and D only