Answer
The use of chlorides to form Grignard reagents is due to their high reactivity and the stability of the carbon-chlorine bond. Chlorides readily undergo nucleophilic substitution reactions with magnesium metal in an ethereal solvent, such as diethyl ether or tetrahydrofuran, to form the corresponding Grignard reagent. This reaction is typically conducted under anhydrous conditions to prevent unwanted side reactions.