An organic compound (X) has the molecular formula C₅H₁₀O. Draw structures for (X) if it: (I) does not give Tollen's test but gives a positive iodoform test; (II) does not give Tollen's test and iodoform test but undergoes Aldol condensation; (III) undergoes Cannizzaro's reaction.

Question

Write the stepwise mechanism of nucleophilic addition reactions in the carbonyl compounds.

Answer 1

Step 1: Read the clues from the formula.
\(C_5H_{10}O\) has one degree of unsaturation, which fits a C=O group, so X is an aldehyde or a ketone.

Step 2: Use the tests as filters.
Tollen's test is positive only for aldehydes. The iodoform test is positive for a \(CH_3CO-\) (methyl ketone) group. Cannizzaro needs an aldehyde with no alpha hydrogen.

Step 3: Solve part (I).
No Tollen's test means it is a ketone, and a positive iodoform test means it is a methyl ketone. The methyl ketone of \(C_5H_{10}O\) is pentan-2-one, \(CH_3COCH_2CH_2CH_3\).

Step 4: Solve part (II).
No Tollen's and no iodoform, but it does Aldol condensation, so it is a ketone that has alpha hydrogens but is not a methyl ketone. Pentan-3-one, \(CH_3CH_2COCH_2CH_3\), fits well.

Step 5: Solve part (III).
Cannizzaro happens with an aldehyde that has no alpha hydrogen. The aldehyde with the carbonyl carbon attached to no alpha H is 2,2-dimethylpropanal (pivaldehyde), \((CH_3)_3C-CHO\).

Answer: (I) Pentan-2-one, \(CH_3COCH_2CH_2CH_3\); (II) Pentan-3-one, \(CH_3CH_2COCH_2CH_3\); (III) 2,2-dimethylpropanal, \((CH_3)_3C-CHO\).

An organic compound (X) has the molecular formula C₅H₁₀O. Draw structures for (X) if it: (I) does not give Tollen's test but gives a positive iodoform test; (II) does not give Tollen's test and iodoform test but undergoes Aldol condensation; (III) undergoes Cannizzaro's reaction.

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Solution and Explanation

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Questions Asked in CBSE Class XII exam

An organic compound (X) has the molecular formula C5H10O. Draw structures for (X) if it: (I) does not give Tollen's test but gives a positive iodoform test; (II) does not give Tollen's test and iodoform test but undergoes Aldol condensation; (III) undergoes Cannizzaro's reaction.

Show Hint

Solution and Explanation

Top Questions on Aldehydes And Ketones

Questions Asked in CBSE Class XII exam

An organic compound (X) has the molecular formula C₅H₁₀O. Draw structures for (X) if it: (I) does not give Tollen's test but gives a positive iodoform test; (II) does not give Tollen's test and iodoform test but undergoes Aldol condensation; (III) undergoes Cannizzaro's reaction.