Propagation Step:Carbon Radical First propagation step H CH H-CI H H methane chlorine atom methyl radical hydrogen chloride Copyright2010 Pearson Prentice Hall,Inc. The chlorine atom collides with a methane molecule and abstracts (removes)an H, forming another free radical and one of the products (HCI). Chapter 4 6
Chapter 4 6 Propagation Step: Carbon Radical The chlorine atom collides with a methane molecule and abstracts (removes) an H, forming another free radical and one of the products (HCl)
Propagation Step:Product Formation Second propagation step H H H- C-CI H H methyl radical chlorine molecule chloromethane chlorine atom Copyright2010 Pearson Prentice Hall,Inc. The methyl free radical collides with another chlorine molecule,producing the organic product(methyl chloride)and regenerating the chlorine radical. Chapter 4 7
Chapter 4 7 Propagation Step: Product Formation The methyl free radical collides with another chlorine molecule, producing the organic product (methyl chloride) and regenerating the chlorine radical
Overall Reaction photon ( :C+C1: First propagation step H H H- H H一C H一CI H H methane chlorine atom methyl radical hydrogen chloride Second propagation step H H H-C. H一C-C CI methyl radical chlorine molecule chloromethane chlorine atom H H HCH+C一CI heat or light H-H-CI+H一C H H methane chlorine chloromethane hydrogen (methyl chloride) chloride Chapter 4 8
Chapter 4 8 Overall Reaction
Termination Steps H H H H H A reaction is classified as a termination step when any two free radicals join together producing a nonradical compound. Combination of free radical with contaminant or collision with wall are also termination steps. Chapter4 9
Chapter 4 9 Termination Steps • A reaction is classified as a termination step when any two free radicals join together producing a nonradical compound. • Combination of free radical with contaminant or collision with wall are also termination steps
More Termination Steps H一( C H CI-CI H HH ·CH H一C一C一H H H HH H H H collides with wall wall H H Cl·collides with wall wall Copyright 2010 Pearson Prentice Hall,Inc Chapter 4 10
Chapter 4 10 More Termination Steps