Final answer:
In the Wittig reaction to synthesize 2-methyl-2-pentene, a phosphonium ylide and a carbonyl-containing molecule, such as an aldehyde or a ketone, are needed as reactants.
Step-by-step explanation:
The reactants needed for the Wittig reaction to synthesize 2-methyl-2-pentene are a phosphonium ylide and a carbonyl-containing molecule. In this case, the carbonyl-containing molecule should be an aldehyde or a ketone. The phosphonium ylide is usually generated from a phosphine and an alkyl halide. For example, one possible combination of reactants could be triphenylphosphine and methyl iodide to form the phosphonium ylide, which can then react with an aldehyde or ketone to produce 2-methyl-2-pentene.