Question

Show how you might synthesize the following compounds starting with bromobenzene, and alkyl or alkenyl halides of four carbon atoms or fewer.

a. 3-phenylprop-1-ene

b.5-methylhex-2-ene

c. dec-5-ene

Short answer

a)

b)

c)

Step-by-step solution

Grignard reaction

Grignard reaction is a typical reaction that involves the addition of magnesium metal to alkyl halides.Further reaction with alkenyl halides results in the formation of alkenes.

Synthesis of 3-phenylprop-1-ene

a) When bromobenzene is treated with Mg in the presence of ether solvent, then Grignard reagent is formed (RMgBr, where R is benzene). Further, on reaction with CH₂=CHCH₂Br forms 3-phenylprop-ene (product)

Synthesis of 3-phenylprop-1-ene

Synthesis of 5-methylhex-2-ene

b) When 2-bromopropane is treated with Mg in the presence of ether solvent, then Grignard reagent is formed (RMgBr). Further, on reaction with CH₃CH=CHCH₂Br, the product formed is 5-methylhex-2-ene (product).

Synthesis of 5-methylhex-2-ene

Synthesis of dec-5-ene

c) When bromopropane is treated with Mg in the presence of ether solvent, the Grignard reagent is formed (RMgBr, where R is CH₃CH₂CH₂). Further, on reaction with Br-CH₂CH=CHCH₂-Br, the product formed is dec-5-ene (product).

Synthesis of dec-5-ene