The correct answer is Option (3) → (A), (B), (C) and (D)
The reagents used in the hydroboration-oxidation of propene involve a two-step chemical process that converts an alkene into a primary alcohol.
The Two-Step Process
- Hydroboration (Step 1): Propene ($\text{CH}_3\text{CH}=\text{CH}_2$) reacts with diborane ($B_2H_6$). Diborane acts as a source of borane ($BH_3$), which adds across the double bond.
- The boron atom attaches to the less substituted terminal carbon (anti-Markovnikov addition).
- This step results in the formation of a trialkylborane intermediate.
- Oxidation (Step 2): The intermediate is treated with hydrogen peroxide ($H_2O_2$) in the presence of an aqueous base (providing $OH^-$ ions), such as sodium hydroxide ($\text{NaOH}$).
- This replaces the boron group with a hydroxyl group ($-\text{OH}$).
- Water ($H_2O$) is used as the solvent for the basic medium and is involved in the hydrolysis of the borate esters to finally yield 1-propanol.
Analysis of Reagents
Based on the mechanism, all four listed substances are involved in the complete sequence:
- (A) $B_2H_6$: The reagent for the hydroboration step.
- (B) $H_2O$: The solvent and source of protons in the basic workup.
- (C) $H_2O_2$: The oxidizing agent that replaces boron with oxygen.
- (D) $OH^-$: The base required to activate the peroxide and catalyze the oxidation.
Therefore, the correct answer is: (A), (B), (C) and (D) |
