H Propagation Step (1)HN The chlorine atom collides with a methane molecule and abstracts (removes)a H, forming another free radical and one of the products(Hcl) H +:C HC·+H-Cl Chapter 4
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). C H H H H + Cl C H H H + H Cl =>
H Propagation Step(2) C——H The methyl free radical collides with another chlorine molecule, producing the other product (methyl chloride) and regenerating the chlorine radical H H H- Cl-Cl H 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. C H H H + Cl Cl C H H H Cl + Cl =>
Overall reaction H + C—H H iC: Cl+ photon(hv) Cl +: Cl +:Cl HC·+H-Cl H ClCl HC-Cl+Cl· H H—C-H+C-Cl—>H-C-C1+H-Cl= H Chapter 4
Chapter 4 8 Overall Reaction C H H H H + Cl C H H H + H Cl C H H H + Cl Cl C H H H Cl + Cl C H H H H + Cl Cl C H H H Cl + H Cl => Cl Cl + photon (h) Cl + Cl
Termination Steps H C-h Collision of any two free radicals Combination of free radical with contaminant or collision with wall H HC°+Cl H-C—Cl H Can you suggest others? Chapter 4
Chapter 4 9 Termination Steps • Collision of any two free radicals • Combination of free radical with contaminant or collision with wall. C H H H + Cl C H H H Cl Can you suggest others? =>
H Equilibrium constant H Keg= products reactants For chlorination Keg =1.1 x 1019 Large value indicates reaction "goes to completion.” Chapter 4
Chapter 4 10 Equilibrium constant • Keq = [products] [reactants] • For chlorination Keq = 1.1 x 1019 • Large value indicates reaction “goes to completion.” =>