Free radical substitution products of methane are successive chlorinated methanes

Steps:

• Free radical chlorination of methane replaces H atoms with Cl stepwise: CH4 to CH3Cl, then CH2Cl2, CHCl3, and CCl4 with excess Cl2.
• Primary products under standard conditions are CH3Cl, CH2Cl2, CHCl3; CCl4 forms only with excess chlorine.
• Side reactions produce minor C2H6 via CH3• coupling, but not chlorinated dimers like C2H5Cl.
• Option D lists only the standard stepwise substitution products without side or excess-required compounds.

Why D is correct:

• CH3Cl, CH2Cl2, CHCl3 result from successive propagation steps: R• + Cl2 → RCl + Cl•, where R is CH3-, CH2Cl-, CHCl2-.

Why the others are wrong:

• A: C2H6 forms via 2 CH3• → C2H6 termination, not substitution.
• B: CCl4 requires excess Cl2 for complete tetrachlorination of methane.
• C: C2H5Cl derives from ethane chlorination, not methane substitution.

Final answer: D