See image — Alcohols Phenols and Ethers Chemistry Question

💡 Solution & Explanation

3-methylbutanal has the structure (CH3)2CHCH2CHO — a 4-carbon chain with a methyl branch at C3 and an aldehyde group at C1. Step 1 — Identify the functional group. 3-methylbutanal ends in -al, meaning it has a terminal aldehyde (–CHO) group. This classifies it as an aldehyde, making option A TRUE. It is NOT a ketone (the carbonyl is terminal, not between two carbons), so option B is FALSE. Step 2 — Aldol reaction with NaOH (option C). Aldehydes with alpha-hydrogens undergo aldol condensation in the presence of NaOH. 3-methylbutanal has alpha-hydrogens (the –CH2– adjacent to the CHO). Therefore an aldol reaction does occur, making option C TRUE. Step 3 — Reaction with LiAlH4 (option D). LiAlH4 is a strong reducing agent that reduces aldehydes to primary alcohols. 3-methylbutanal would be reduced to 3-methyl-1-butanol. So there IS a reaction, making option D FALSE. Step 4 — Reaction with excess CH3MgBr (option E). CH3MgBr (methylmagnesium bromide) adds to the aldehyde carbonyl. The aldehyde carbon is C1; adding a methyl group from CH3MgBr to the carbonyl carbon of (CH3)2CHCH2CHO gives, after workup, (CH3)2CHCH2CH(OH)CH3. Numbering this product: the longest chain containing the OH gives 4-methyl-2-pentanol. This is a secondary alcohol with the OH at C2 and a methyl branch at C4. So option E is TRUE. Step 5 — Wolff-Kishner reduction (option F). Wolff-Kishner reduction converts a carbonyl group (C=O) to a CH2 group. Applied to 3-methylbutanal (CH3)2CHCH2CHO, the –CHO becomes –CH3, giving (CH3)2CHCH2CH3, which is 2-methylbutane (isopentane), NOT butane. Butane is a straight 4-carbon chain. Option F is FALSE. Step 6 — Isomer of 3-pentanone (option G). 3-methylbutanal: molecular formula C5H10O. 3-pentanone (CH3CH2COCH2CH3): molecular formula C5H10O. Both have the same molecular formula C5H10O, so they are constitutional isomers. Option G is TRUE. Summary: A (TRUE), B (FALSE), C (TRUE), D (FALSE), E (TRUE), F (FALSE), G (TRUE). Therefore, the correct answer is A,C,E,G.