The compounds that produce $$CO_{2}$$ with aqueous $$NaHCO_{3}$$ solution are:
A. 

B. 

C. 

D. 

E. 

Choose the correct answer from the options given below:

The test with aqueous $$NaHCO_{3}$$ is an acid-base reaction. It is positive (effervescence of $$CO_{2}$$) only for those organic compounds whose acidity is stronger than that of carbonic acid $$\bigl($$ $$pK_{a}\,\approx\,6.37$$ $$\bigr)$$. In the syllabus this essentially restricts the list to:

• Carboxylic acids $$\left( \,\ce{R-COOH}\, \right)$$
• Sulfonic acids $$\left( \,\ce{R-SO_{3}H}\, \right)$$ (rare in JEE questions)
Phenols, enols, alcohols, aldehydes and ketones are all too weakly acidic to react with $$NaHCO_{3}$$.

Now inspect the five compounds given in the question:

Case A: The molecule contains a carboxyl group $$\left( -COOH \right)$$, so it will release $$CO_{2}$$.
Case B: No carboxyl (or sulfonic) group is present; it will not react with $$NaHCO_{3}$$.
Case C: This structure also possesses a $$-COOH$$ group, therefore it will effervesce.
Case D: The compound again has a carboxylic acid functionality and will give the test.
Case E: Absent of any strongly acidic group, hence no reaction with $$NaHCO_{3}$$.

Thus only compounds A, C and D satisfy the condition.

Option A which is: A, C and D Only