See image — Alcohols Phenols and Ethers Chemistry Question

💡 Solution & Explanation

3-methyl-2-butanone has the structure: CH3-CO-CH(CH3)2 (a ketone with molecular formula C5H10O). Option A: CrO3 oxidation of 2-methyl-2-butanol. 2-methyl-2-butanol is (CH3)2C(OH)-CH2CH3, a tertiary alcohol. Tertiary alcohols cannot be oxidized by CrO3 (they have no H on the carbon bearing OH). So option A is FALSE. Option B: Reaction of 3-methyl-2-butanone with NaBH4. NaBH4 reduces ketones to secondary alcohols. Reducing CH3-CO-CH(CH3)2 gives CH3-CH(OH)-CH(CH3)2, which is 3-methyl-2-butanol — a secondary alcohol (OH on C2, which bears both C1 and C3 substituents). So option B is TRUE. Option C: Acidic Hg2+ catalyzed hydration of 3-methyl-1-butyne. 3-methyl-1-butyne is HC≡C-CH(CH3)2. Markovnikov addition of water to the terminal alkyne (with Hg2+/H+) places OH on C2 (more substituted carbon), giving the enol CH2=C(OH)-CH(CH3)2, which tautomerizes to the ketone CH3-CO-CH(CH3)2, i.e., 3-methyl-2-butanone. So option C is TRUE. Option D: Silver mirror test with [Ag(NH3)2]+. This is Tollens' reagent, which is only positive for aldehydes (and some alpha-hydroxy ketones), not for simple ketones. 3-methyl-2-butanone is a ketone with no aldehyde functionality, so it does NOT give a silver mirror. Option D is FALSE. Option E: Is 3-methyl-2-butanone an isomer of 4-penten-1-ol? 3-methyl-2-butanone: C5H10O. 4-penten-1-ol: CH2=CH-CH2-CH2-CH2OH, molecular formula C5H10O. Both have the same molecular formula C5H10O, so they are constitutional isomers. Option E is TRUE. Therefore, the correct answer is B,C,E.