The addition of HBr to 1,3-butadiene gives two products. One of the products is shown below. Identify the second product.
The Correct Answer and Explanation is :
The reaction of HBr with 1,3-butadiene is a typical example of an electrophilic addition reaction. 1,3-Butadiene (CH₂=CH-CH=CH₂) contains two conjugated double bonds, meaning they are adjacent to each other. When HBr is added to 1,3-butadiene, two different products can form due to the regioselectivity of the addition and the resonance stability of the intermediates involved.
The addition can occur in two ways, leading to two possible products:
- Markovnikov’s Addition: The Br atom adds to the carbon atom of the double bond that has the greater number of hydrogen atoms already attached to it. This results in the formation of the more stable carbocation intermediate because the tertiary carbocation is more stable than the secondary one.
- Anti-Markovnikov’s Addition (via a resonance-stabilized intermediate): The addition can proceed via a different mechanism where the Br adds to the less substituted carbon. This process involves the formation of a less stable secondary carbocation that rearranges to a more stable conjugated intermediate, which leads to the product.
In this case, the image you’ve provided shows one of the products, which is 3-bromo-1-butene. This product results from the Markovnikov addition where the Br atom adds to the more substituted carbon (C3), and the hydrogen adds to the C1 position.
The second product is 1-bromo-2-butene, formed by the Anti-Markovnikov addition. In this case, the Br adds to the less substituted carbon (C1) of the conjugated double bond, and the hydrogen adds to the C2 position.
In summary:
- Product 1 (Markovnikov’s addition): 3-bromo-1-butene.
- Product 2 (Anti-Markovnikov’s addition): 1-bromo-2-butene.
Both products arise due to the reaction of HBr with the conjugated diene in 1,3-butadiene, with the regioselectivity of the addition governed by the stability of the carbocation intermediates.
Now, let me generate an image of the structure of both products for you.
Here is the chemical diagram showing the two products of the HBr addition to 1,3-butadiene: 1-bromo-2-butene and 3-bromo-1-butene. Let me know if you need further clarification!
