Question

Show how you would synthesize the following compounds, starting with benzene or toluene and any necessary acyclic reagents. Assume para is the major product (and separable from ortho) in ortho, para mixturesortho) in ortho, para mixtures.I-phenyl-1-bromobutane

Answer 1

The synthesis of 1-phenyl-1-bromobutane from benzene involves a Friedel-Crafts alkylation to form ethylbenzene, followed by reaction with a Grignard reagent to extend the carbon chain, dehydration to form an alkene, and an addition reaction with HBr to attach the bromine.

Step-by-step explanation:

To synthesize 1-phenyl-1-bromobutane starting from benzene, one approach involves several steps to first form the phenyl group containing compound, followed by an extension of the carbon chain, and finally adding the bromine. Here is a step-by-step synthesis:

1. Benzene undergoes alkylation via a Friedel-Crafts reaction to form ethylbenzene. This can be done by reacting benzene with chloroethane in the presence of an aluminum chloride catalyst (AlCl3).
2. The ethylbenzene formed is then reacted with methylmagnesium bromide (a Grignard reagent) resulting in a tertiary alcohol.
3. This tertiary alcohol subsequently undergoes dehydration to form a 1-phenyl-1-butene (alkene).
4. The alkene then undergoes an addition reaction with hydrogen bromide (HBr) to yield 1-phenyl-1-bromobutane.

It is important to note that each reaction should be done under appropriate conditions, for example, the Friedel-Crafts reaction should be done under anhydrous conditions to prevent the aluminum chloride from hydrolyzing.