Which of the following reactions will not give \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{OCH}_{3}\), as the product? (a) \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{OH}+\mathrm{CH}_{3} \mathrm{Br} \stackrel{\mathrm{NaOH}}{\longrightarrow}\) (b) \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{OH}+\left(\mathrm{CH}_{3}\right)_{2} \mathrm{SO}_{4} \stackrel{\mathrm{NaOH}}{\longrightarrow}\) (c) \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{OH}+\mathrm{CH}_{2} \mathrm{~N}_{2} \longrightarrow\) (d) \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{OH}+\mathrm{CH}_{3} \mathrm{MgBr} \longrightarrow\)

Williamson Ether Synthesis is a fundamental organic reaction forming an ether from an organohalide and an alcohol. This two-step process begins with the deprotonation of the alcohol to form an alkoxide ion, which is a powerful nucleophile. In the case of phenol, which is more acidic than typical alcohols, treatment with a base like NaOH readily forms the phenoxide ion.

Next, the alkoxide ion attacks an alkyl halide in a nucleophilic substitution reaction to form the ether. In the textbook example, the phenoxide ion reacts with methyl bromide, a primary alkyl halide, to yield anisole. It's a classic example of nucleophilic substitution (specifically, an S_N2 reaction) to form ethers—a critical reaction type in organic Synthesis that allows for the creation of a wide variety of complex molecules.

Methylating agents are chemicals used to transfer a methyl group to another molecule. Dimethyl sulfate, the methylating agent used in the textbook example, is one such chemical that is frequently utilized for its ability to donate methyl groups in the formation of ethers and other organic compounds.

These agents are typically strong electrophiles, meaning they are electron-deficient and can react with nucleophiles, such as phenoxide ions. Methylating agents serve an essential role in organic Synthesis, particularly in the methylation of alcohols, phenols, amines, and other nucleophiles. This capability is markedly useful in modifying the structure and properties of organic compounds. For students grasping textbook solutions, it's important to recognize the role of these agents and the conditions under which they operate effectively.

Grignard reagents are a class of organometallic compounds that are invaluable in organic Synthesis. Comprising of an alkyl, vinyl, or aryl group bonded to a magnesium halide, these reagents are highly nucleophilic and react with a variety of electrophiles.

In the context of our example, a Grignard reagent, such as methylmagnesium bromide (CH₃MgBr), reacts with phenol. However, because Grignard reagents are also strong bases, they tend to deprotonate acidic hydrogens. Phenol, with its relatively acidic hydrogen, is deprotonated rather than undergoing a nucleophilic attack to form an ether. Instead of yielding anisole as might be expected with other methylating agents or under Williamson Ether Synthesis conditions, the reaction leads to a biphenyl compound and magnesium salts. When studying organic chemistry reactions, understanding the dual nature of Grignard reagents as both bases and nucleophiles is crucial for predicting reaction outcomes.