Consider the following sequence of reactions:

The final product is `C` is

Options

A.
B.
C. `Ph_(3)P=CHCH_(3)`
D. `Ph_(3)overset(+)PCH_(2)CH_(3)Br`

Answer

B

Explanation

It is an example of a Witting reaction. The phosphorane or phosphorus ylide is prepared by the alkylation of triphenylphosphine with alkyl halides having at least one `alpha-H` atom. The resulting phosphonium halide on treatment with an alkali in an inert solvent like xylene forms phosphorane or the phosphorus ylide. The phosphorus ylide reacts with a carbonyl group to form an oxaphosphetane via a betaine. The oxaphosphetane undergoes a cyclo-elimination reaction to give the desired alkene and `Ph_(3)PO`.