An organic compound "P" of molecular formula \(C_7H_{12}O\) (likely \(C_7H_{12}O_2\) or similar based on options), gives positive Iodoform test but negative Tollen's test. When "P" is treated with dilute acid, it produces "Q". "Q" gives positive Tollen's test and also Iodoform test. The structure of "P" is:
Show Hint
Acetals are stable to base but hydrolyze in dilute acid to regenerate carbonyl compounds. This is a common method to "protect" aldehydes.
• Iodoform test (Positive):
This indicates that compound P contains either a methyl ketone group
\(CH_3–CO–\) or a methyl carbinol group
\(CH_3–CH(OH)–\).
• Tollen’s test (Negative):
This shows that compound P does not contain an aldehyde group.
Step 2: Reaction Analysis and Identification of Compound Q
• Reaction:
Compound P on treatment with dilute acid gives compound Q.
This indicates an acid-catalysed hydrolysis, most likely of an acetal, ketal, or enol ether group.
• Properties of Q:
– Tollen’s test (Positive):
Compound Q contains an aldehyde group
\((-CHO)\).
– Iodoform test (Positive):
Compound Q also contains a methyl ketone group
\((CH_3–CO–)\).
Hence, compound Q must contain both an aldehyde and a methyl ketone group.
A suitable structure is 3-oxobutanal,
\(CH_3–CO–CH_2–CHO\).
Step 3: Deduction of Compound P
Since P does not give Tollen’s test but gives iodoform test, the aldehyde group in Q must be protected in P, while the ketone group remains unchanged.
Therefore, P is the dimethyl acetal of the aldehyde group of Q:
\[
CH_3–CO–CH_2–CH(OCH_3)_2
\]
• Verification for P:
– Contains a ketone group → Iodoform test positive
– Aldehyde is protected as acetal → Tollen’s test negative
• Hydrolysis reaction:
\[
CH_3–CO–CH_2–CH(OCH_3)_2
\xrightarrow{H_3O^+}
CH_3–CO–CH_2–CHO + 2CH_3OH
\]
• Verification for Q:
– Aldehyde present → Tollen’s test positive
– Methyl ketone present → Iodoform test positive
Thus, compound P is the acetal derivative of 3-oxobutanal, corresponding to Option 2.
Was this answer helpful?
0
Top Questions on Organic Compounds and Hydrogenation
