Question

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?

Answer 1

2-Methyl-2-butene can be synthesized using Wittig reaction in following steps;

1) First of all react Bromoethane with Triphenylphosphine which will undergo SN² reaction to produce Phosphonium salt. Phoshonium salt on treatment with base gives Phosphorous Ylide.

2) The ylide formed when treated with acetone forms a four membered ring intermediate, which readily rearranges to produce 2-methyl-2-butene and triphenylphosphine oxide.

Result:
Starting materials are...

1) Bromoethane

2) Acetone

3) Triphenyl phosphene