See image — Reaction Mechanism Chemistry Question

💡 Solution & Explanation

Concept: Grignard reagents add to carbonyl compounds to give alcohols after hydrolysis. The product is tert-Pentyl alcohol (2-methyl-2-butanol), which has the structure (CH3)2C(OH)CH2CH3, i.e., a tertiary alcohol with the carbon skeleton: two methyl groups and one ethyl group attached to the carbon bearing the OH. Step 1: Identify tert-Pentyl alcohol. tert-Pentyl alcohol is 2-methyl-2-butanol: (CH3)2C(OH)CH2CH3. The central carbon (C2) bears: OH, CH3, CH3, and CH2CH3. Step 2: The Grignard reagent used is C2H5MgI (ethylmagnesium iodide), which contributes a –CH2CH3 (ethyl) group. Step 3: In a Grignard reaction, the Grignard reagent (nucleophile) attacks the carbonyl carbon of compound A, and after hydrolysis (H2O/H+) gives the alcohol B = tert-Pentyl alcohol. The carbon from the carbonyl compound A becomes the carbon bearing OH in the product. Step 4: The product carbon (C bearing OH) has: the two groups originally on the carbonyl carbon of A, plus the ethyl group from the Grignard, plus OH. For tert-Pentyl alcohol: the C bearing OH has two methyls and one ethyl. The Grignard contributes the ethyl group. Therefore, compound A must have two methyl groups on the carbonyl carbon, i.e., A is acetone: (CH3)2C=O. Step 5: Verify: Acetone (CH3)2C=O + C2H5MgI → (CH3)2C(OMgI)(C2H5) --H2O/H+--> (CH3)2C(OH)(C2H5) = 2-methyl-2-butanol = tert-Pentyl alcohol. ✓ Why other options fail: - (a) 2-Butanone (CH3COC2H5): Grignard addition of C2H5 gives CH3C(OH)(C2H5)2 = 3-methyl-3-pentanol, not tert-Pentyl alcohol. - (b) Acetaldehyde (CH3CHO): Grignard addition of C2H5 gives CH3CH(OH)C2H5 = 2-butanol, a secondary alcohol, not tert-Pentyl alcohol. - (d) Propanal (CH3CH2CHO): Grignard addition of C2H5 gives CH3CH2CH(OH)C2H5 = 3-pentanol, a secondary alcohol, not tert-Pentyl alcohol. Therefore, the correct answer is C.