Organic Chemistry, 5th Edition H C——H L G. Wade Jr H Chapter 4 The study of Chemical Reactions Jo blackburn Richland College, Dallas, TX Dallas County Community College District C 2003. Prentice hall
Chapter 4 The Study of Chemical Reactions Jo Blackburn Richland College, Dallas, TX Dallas County Community College District ã 2003, Prentice Hall Organic Chemistry, 5th Edition L. G. Wade, Jr
H Tools for Study + C—H H To determine a reactions mechanism look at >Equilibrium constant >Free energy change >Enthalpy >Entropy >Bond dissociation energy >Kinetics >Activation energy Chapter 4
Chapter 4 2 Tools for Study • To determine a reaction’s mechanism, look at: ØEquilibrium constant ØFree energy change ØEnthalpy ØEntropy ØBond dissociation energy ØKinetics ØActivation energy =>
H Chlorination of Methane HA heat or light H-C-H CI H--C-CI HCl Requires heat or light for initiation The most effective wavelength is blue, which is absorbed by chlorine gas Lots of product formed from absorption of only one photon of light (chain reaction Chapter 4
Chapter 4 3 Chlorination of Methane • Requires heat or light for initiation. • The most effective wavelength is blue, which is absorbed by chlorine gas. • Lots of product formed from absorption of only one photon of light (chain reaction). => C H H H H + Cl2 heat or light C H H H Cl + HCl
H Free-Radical chain reaction C——H Initiation generates a reactive intermediate Propagation the intermediate reacts with a stable molecule to produce another reactive intermediate(and a product molecule Termination side reactions that destroy the reactive intermediate Chapter 4
Chapter 4 4 Free-Radical Chain Reaction • Initiation generates a reactive intermediate. • Propagation: the intermediate reacts with a stable molecule to produce another reactive intermediate (and a product molecule). • Termination: side reactions that destroy the reactive intermediate. =>
H Initiation Step C——H H A chlorine molecule splits homolytically into chlorine atoms(free radicals) :C: C:+ photon(hv) Cl t Cl. Chapter 4
Chapter 4 5 Initiation Step A chlorine molecule splits homolytically into chlorine atoms (free radicals) => Cl Cl + photon (h) Cl + Cl