CH4 + Cl2 → CH3Cl + HCl is an example of which reaction type?

CH4 + Cl2 → CH3Cl + HCl is an example of which reaction type?

• A. Addition
• B. Elimination
• C. Substitution
• D. Combustion

Answer: (D)

Substitution (halogenation) of methane. In this reaction, one hydrogen atom in methane is replaced by a chlorine atom when chlorine gas and light are present. The mechanism involves chlorine radicals: a Cl• abstracts a hydrogen from CH4 to give HCl and a CH3• radical, and then CH3• reacts with another Cl2 molecule to form CH3Cl and another Cl•, continuing the chain. This replacement of H with Cl makes it a substitution process, not addition (no multiple bond to add across), not elimination (no formation of a double bond by removing a small molecule), and not combustion (no oxygen, no oxidation to CO2/H2O).

Substitution (halogenation) of methane. In this reaction, one hydrogen atom in methane is replaced by a chlorine atom when chlorine gas and light are present. The mechanism involves chlorine radicals: a Cl• abstracts a hydrogen from CH4 to give HCl and a CH3• radical, and then CH3• reacts with another Cl2 molecule to form CH3Cl and another Cl•, continuing the chain. This replacement of H with Cl makes it a substitution process, not addition (no multiple bond to add across), not elimination (no formation of a double bond by removing a small molecule), and not combustion (no oxygen, no oxidation to CO2/H2O).