Propagation steps regenerate radicals in free radical chlorination

Steps:

• Free radical chlorination has initiation (Cl₂ → 2Cl•), propagation (radical + molecule → product + radical), and termination.
• First propagation: chlorine radical abstracts hydrogen from ethane, forming ethyl radical and HCl.
• Second propagation: ethyl radical reacts with Cl₂, forming chloroethane and chlorine radical.
• Valid steps maintain the radical chain without net consumption of radicals.

Why B and C are correct:

• Both follow the propagation rule: a radical reacts with a stable molecule to yield a stable product and new radical, sustaining the chain reaction per free radical mechanism.

Why the others are wrong:

• A: Cl• does not abstract Cl from CH₃CH₂Cl to form HCl; it prefers H-abstraction, making this unfavorable and non-propagating.
• D: Equation unbalanced (6 H on left, 5 on right); resembles faulty initiation, not propagation.

Final answer: B and C