Question

What is the product formed when CH₃–CH=CH₂ is treated with B₂H₆ followed by the action of H₂O₂?

• A. CH₃CH₂CH₂OH
• B. CH₃CH₂CH₃
• C. CH₃CH₂CHO
• D. CH₃CH(OH)CH₃

Answer 1

The Correct Option is A

Concept:
The reaction described involves the use of diborane (B₂H₆) followed by hydrogen peroxide (H₂O₂), a common synthetic method known as hydroboration-oxidation. This reaction is typically used to convert alkenes into alcohols with specific regioselectivity.

Reaction Overview:
In this reaction, propene (CH₃–CH=CH₂) reacts with diborane (B₂H₆), which adds across the double bond. This step leads to the formation of an organoborane intermediate. Then, the organoborane is treated with hydrogen peroxide (H₂O₂) in the presence of a base, which replaces the boron atom with a hydroxyl group, resulting in the formation of an alcohol.

The reaction proceeds as follows:
- Step 1: Hydroboration: Diborane (B₂H₆) adds across the double bond of propene. The boron atom adds to the carbon atom of the double bond that has the fewest hydrogen atoms (anti-Markovnikov addition), and the hydrogen atom adds to the carbon with the most hydrogen atoms.
- Step 2: Oxidation: The organoborane intermediate is treated with hydrogen peroxide (H₂O₂) and a base (such as NaOH), replacing the boron atom with a hydroxyl group (-OH), forming a primary alcohol.

Specific Product:
The product of this reaction is 1-propanol (CH₃CH₂CH₂OH). The reaction selectively produces the alcohol at the position of the original double bond, and because of the anti-Markovnikov rule, the hydroxyl group (–OH) is added to the terminal carbon of the propene molecule.

Reaction Mechanism:
1. Hydroboration Step: B₂H₆ adds across the double bond of propene, leading to the formation of an organoborane intermediate.
2. Oxidation Step: The organoborane is treated with hydrogen peroxide and a base (NaOH) to replace the boron atom with a hydroxyl group, resulting in the formation of 1-propanol.

Conclusion:
The product formed when CH₃–CH=CH₂ (propene) is treated with diborane (B₂H₆) followed by the action of hydrogen peroxide (H₂O₂) is 1-propanol (CH₃CH₂CH₂OH). This is a classic example of the hydroboration-oxidation reaction.

Therefore, the correct product is: (A) 1-propanol.