See image — Alcohols Phenols and Ethers Chemistry Question

💡 Solution & Explanation

Step 1 - Concept: Grignard reagents (RMgX) act as nucleophiles, adding to electrophilic carbonyl carbons (aldehydes, ketones) or epoxides to give alcohols after aqueous acid workup. The type of alcohol produced depends on the substrate A. Step 2 - PCC test: PCC (pyridinium chlorochromate) in dichloromethane oxidizes primary alcohols to aldehydes and secondary alcohols to ketones, but does NOT react with tertiary alcohols. Since compound B does not react with PCC, B must be a tertiary alcohol. Step 3 - Grignard addition to a ketone gives a tertiary alcohol: When CH3CH2MgI (ethyl Grignard) adds to a ketone, the ethyl group adds to the carbonyl carbon, which already bears two carbon substituents, yielding a tertiary alcohol after protonation. Step 4 - Evaluate option (b): Substance A = CH3CH2C(=O)CH3 (methyl ethyl ketone, butanone). The Grignard (CH3CH2-) attacks the carbonyl carbon of CH3CH2C(=O)CH3, giving the alkoxide CH3CH2C(O^-)(CH2CH3)CH3 after addition, then protonation gives CH3CH2C(OH)(CH2CH3)CH3 = 3-methyl-3-pentanol, a tertiary alcohol. This tertiary alcohol cannot be oxidized by PCC. This matches the condition. Step 5 - Eliminate other options: (a) CH3CHO (acetaldehyde) is an aldehyde; Grignard addition gives a secondary alcohol (CH3CH(OH)CH2CH3), which PCC can oxidize to a ketone. Fails the test. (c) H2C=O (formaldehyde) gives a primary alcohol (CH3CH2CH2OH) after Grignard addition, which PCC oxidizes to an aldehyde. Fails the test. (d) Ethylene oxide gives a primary alcohol (CH3CH2CH2CH2OH after ring opening), oxidizable by PCC. Fails the test. Step 6 - Conclusion: Only option (b), a ketone, produces a tertiary alcohol with the ethyl Grignard, consistent with no reaction with PCC. Therefore, the correct answer is B.