The structure of 2-methylbut-2-ene can be determined by identifying the location of the double bond and the position of the methyl group. The name indicates that there are four carbon atoms in the main chain, with a methyl group attached to the second carbon and the double bond between the second and third carbon.
Looking at the options, it can be seen that option A and B have the double bond between the first and second carbon, which is incorrect. Option C has the correct position of the double bond, but the methyl group is attached to the first carbon instead of the second carbon. Therefore, the correct structure for 2-methylbut-2-ene is option D, where the double bond is between the second and third carbon and the methyl group is attached to the second carbon.
