H Propagation Step (1) The chlorine atom collides with a methane molecule and abstracts (removes)a H, forming another free radical and one of the products (HCI). First propagation step H H H-CE H-C. H-CI H H methane chlorine atom methyl radical hydrogen chloride Copyright 2005 Pearson Prentice Hall,Inc. 三> Chapter 4 6
Chapter 4 6 Propagation Step (1) The chlorine atom collides with a methane molecule and abstracts (removes) a H, forming another free radical and one of the products (HCl). =>
H Propagation Step(2) p H The methyl free radical collides with another chlorine molecule,producing the other product(methyl chloride)and regenerating the chlorine radical. Second propagation step H H H methyl radical chlorine molecule chloromethane chlorine atom Copyright@2005 Pearson Prentice Hall,Inc. Chapter 4
Chapter 4 7 Propagation Step (2) The methyl free radical collides with another chlorine molecule, producing the other product (methyl chloride) and regenerating the chlorine radical. =>
Overall Reaction H.. H g:+ photon(hv) Ci. H H H H-C· H一CI H H H H CI- H H H H C-H CI-CI heat or light +H一C H => Chapter 4 8
Chapter 4 8 Overall Reaction =>
Termination Steps H.. sP: Collision of any two free radicals. H Combination of free radical with contaminant or collision with wall. H H H H H H Can you suggest others? => Chapter 4 9
Chapter 4 9 Termination Steps • Collision of any two free radicals. • Combination of free radical with contaminant or collision with wall. Can you suggest others? =>
H. Equilibrium Constant ·Kea=[products] [reactants] For chlorination Keg=1.1 x 1019 ·Large value indicates reaction“goes to completion.” => Chapter 4 10
Chapter 4 10 Equilibrium Constant • Keq = [products] [reactants] • For chlorination Keq = 1.1 x 1019 • Large value indicates reaction “goes to completion.” =>