Question

Which one of the following undergoes iodoform test?

• A. Propanal
• B. Ethanal
• C. Benzophenone
• D. Benzaldehyde
• E. Phenol

Hint:

Look for \(CH_3CO-\) or \(CH_3CH(OH)-\) group for iodoform test.

Answer 1

The Correct Option is B

Understanding the Concept: Iodoform test is given by compounds containing: \[ -COCH_3 \quad \text{(methyl ketone)} \quad \text{or} \quad CH_3CH(OH)- \]

Step 1: Understand reaction. \[ RCOCH_3 + I_2 + NaOH \rightarrow CHI_3 \downarrow + \text{other products} \] Yellow precipitate of iodoform confirms the test.

Step 2: Analyze each option. (A) Propanal: Structure: \(CH_3CH_2CHO\) Does not contain \(CH_3CO-\) group → no reaction. (B) Ethanal: Structure: \(CH_3CHO\) This behaves like methyl ketone in haloform reaction → gives iodoform. (C) Benzophenone: No methyl ketone group → no reaction. (D) Benzaldehyde: Aromatic aldehyde → no iodoform test. (E) Phenol: No carbonyl → no reaction. Final Final Answer: \[ \boxed{\text{Ethanal gives iodoform test}} \]