Free-Radical Chlorination of Methane

Also called

free radical chlorination · chlorination of methane · halogenation of alkanes · free radical mechanism · free radical substitution · chain reaction · homolytic fission · homolysis · initiation propagation termination · methyl radical · chlorine free radical · chloromethane · dichloromethane · chloroform · carbon tetrachloride · UV light reaction · मुक्त मूलक · हैलोजनीकरण · श्रृंखला अभिक्रिया

Topics

• Methane and chlorine do not react in the dark; in UV light or diffused sunlight they give CH₃Cl and HCl.
• Initiation: light breaks the Cl–Cl bond evenly (homolysis), each atom keeping one electron: Cl₂ → 2Cl·.
• A free radical is an atom or group with an unpaired electron, so it is very reactive.
• Propagation: Cl· + CH₄ → CH₃· + HCl, then CH₃· + Cl₂ → CH₃Cl + Cl·.
• Each step makes a new radical, so one photon can start a chain that makes thousands of product molecules.
• Termination: two radicals join, as Cl–Cl, H₃C–CH₃ or H₃C–Cl, and the chain stops.
• Ethane found among the products is evidence that methyl radicals take part.
• Chlorination does not stop at CH₃Cl: further substitution gives CH₂Cl₂, CHCl₃ and CCl₄, a mixture.
• Every substitution swaps one H for one Cl and gives off one molecule of HCl.

About this model

A GLB file of about 380 KB, shown in Lably's 3D viewer and, on a phone, placed in your room with AR. Credit: Model, science and animation: Lably (built procedurally with three.js; no downloaded meshes). | CC BY 4.0. Original geometry and animation made for Lably.

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