The Wittig reaction involves coupling between a phosphonium ylide and a carbonyl-containing molecule. If a chemist wants to use the Wittig reaction to synthesize 2-methyl-2-butene, which reactants should be used? Use the graded interactive module below to explore the reactivity and mechanism of the Wittig reaction and to construct the target product molecule. Click and drag a reactant molecule from each column onto the reaction stage. Note the mechanism of the reaction and the obtained products. After constructing a product compound, use the Reset button to try again or click on Check Answer to assess your product.

Ethyl bromide is treated with [tex]PPh_{3}[/tex] followed by n-BuLi to prepare the required phosphonium ylide.
Acetone is the carbonyl containing molecule for the preparation of 2-methyl-2-butene via wittig reaction.
At first, the phosphonium ylide of ethyl bromide gives a nucleophilic addition reaction with the keto group of acetone to produce a 4-membered cyclic intermediate.
Then the cyclic intermediate undergoes rearrangement to produce 2-methyl-2-butene.
All the steps are shown below.