Question

In Friedel-Crafts alkylation reaction of phenol with chloromethane, the product formed will be

• A. p-cresol only
• B. m-cresol only
• C. mixture of o- and p-cresol
• D. o-cresol only

Hint:

In Friedel-Crafts alkylation of phenol, the electron-donating -OH group directs the alkylation to the ortho and para positions, resulting in a mixture of o- and p-cresol.

Answer 1

The Correct Option is C

The Friedel-Crafts alkylation reaction is a method to introduce an alkyl group into an aromatic compound using an alkyl halide and a Lewis acid such as AlCl₃. In the case of phenol reacting with chloromethane, the mechanism involves the formation of a carbocation from chloromethane, which then undergoes electrophilic aromatic substitution.

Phenol, due to the presence of the hydroxyl group (-OH), is an activated aromatic compound. The -OH group is an ortho-para directing group, which means it increases the electron density on the ortho and para positions of the aromatic ring, making these sites more susceptible to electrophilic attack.

The steps are as follows:

1. Formation of Electrophile: Chloromethane reacts with the Lewis acid (AlCl₃) to form the methyl carbocation (CH₃⁺).
2. Electrophilic Attack: The methyl carbocation attacks the phenol, primarily at the ortho and para positions due to the activating effect of the -OH group.
3. Formation of Products: The main products are o-cresol and p-cresol. The ortho and para positions are more reactive due to increased electron density from the hydroxyl group.

Considering steric and electronic factors, both ortho and para products are formed, resulting in a mixture. The correct answer is: mixture of o- and p-cresol.

Answer 2

In the Friedel-Crafts alkylation reaction of phenol with chloromethane (CH3Cl), the methyl group is introduced into the aromatic ring of phenol. The reaction proceeds through an electrophilic aromatic substitution mechanism.
In this case, the methyl group can be attached to either the ortho (o) or para (p) positions of the phenol ring. 

- The hydroxyl group (-OH) on phenol is an electron-donating group, which activates the aromatic ring and makes the ortho and para positions more reactive toward electrophilic attack. 

- Due to steric and electronic effects, the major product is a mixture of both ortho and para isomers of methylphenol, also known as o-cresol and p-cresol, respectively. 

Thus, the correct answer is mixture of o- and p-cresol.