Which of the following compounds is an example of an alkylating agent?

• A. Phenol ($C_6{H}_5\mathrm{OH}$)
• B. Methyl iodide (${\mathrm{CH}}_{3}I$)
• C. Acetic acid (${\mathrm{CH}}_3\mathrm{COOH}$)
• D. Ethanol (${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{OH}$)

Answer: (B)

Verified step by step guidance

1. Understand what an alkylating agent is: it is a compound that can transfer an alkyl group (a carbon chain fragment) to another molecule, often through a nucleophilic substitution reaction.
2. Examine the structure of each compound to identify if it contains a good leaving group attached to an alkyl group, which is necessary for alkylation.
3. Phenol (C\_6H\_5OH) has an -OH group attached to an aromatic ring, but the hydroxyl group is not a good leaving group for alkylation under normal conditions.
4. Acetic acid (CH\_3COOH) contains a carboxylic acid group, which is not typically involved in alkyl transfer reactions because it does not have a good leaving group attached to an alkyl chain.
5. Methyl iodide (CH\_3I) has a methyl group attached to iodine, a very good leaving group, making it highly reactive in nucleophilic substitution reactions and thus a classic example of an alkylating agent.