Answer:
1-butene
Explanation:
In this case, the problem is already stating and saying the reaction involved here.
1-bromobutane undergoes a dehydrohalogenation in presence of a base. This will cause an elimination reaction forming a product.
As this is an elimination product, this can be done in two ways.
The first way is with an unimolecular reaction where the halide is eliminated from the starting reactant in a two step reaction involving a carbocation formation. This is known as E1 reaction. However, the conditions for this reaction is to be in acid medium.
The second way is with a bimolecular reaction where the halide is eliminated from the starting reactant in just one step, and no carbocation is formed. This is known as E2 reaction and is commonly used with bases.
In the case of this problem, we are undergoing an E2 reaction, therefore, the mechanism of reaction is just one step, and when this happens, the base substract the hydrogen from Carbon 2, eliminates the bromide and forms a double bond, giving the 1-butene.
You can see the mechanism in the following picture.
Hope this helps
