Question

How to prepare 1-phenyl-3-methyl-2-butanol?

Answer 1

Hint: Aromatic compounds (benzene) can have carbon chain added through Friedal-crafts reactions. Organolithium reagents help in nucleophilic addition reactions. Sodium borohydrides are used as reducing agents for carbonyl compounds.

Complete answer:
We have been given to write about the preparation method of 1-phenyl-3-methyl-2-butanol. As the name suggests, this compound contains a benzene ring with a 4-carbon chain on the first carbon of benzene. This 4-carbon chain has a methyl group on carbon-3 and a hydroxyl group on carbon-2, which makes it a secondary alcohol.
The preparation of 1-phenyl-3-methyl-2-butanol involves friedel-craft acylation of benzene employing a catalyst used to synthesis organic compounds called oxalyl chloride\[(COC{{l}_{2}})\] that helps its formation into a carbon chain on position-1. Then the carbonyl adjacent from the benzene on this carbon chain is reduced, while the other carbonyl is unaffected. Then an organolithium reagent $({{C}_{3}}{{H}_{8}}Li)$ is used to carry a nucleophilic addition that removes the chloride group. The last step involves the use of a reducing agent, sodium borohydride $(NaB{{H}_{4}})$ and water that converts the carbonyl into secondary alcohol. Water helps in the addition of the hydrogen to the oxygen anion. The reaction is as follows:

Hence, through the above reaction we can prepare 1-phenyl-3-methyl-2-butanol.

Note:
Friedel-crafts acylation is used in this reaction because; we have to obtain a secondary alcohol, which can be formed from the acyl group. While, friedel-crafts alkylation will be involved if we have to add up only a carbon chain to the benzene ring.