Transcript Chapter 5
Chapter 5 Overview of Organic reaction 5.1 Kinds of Organic reactions • Addition reaction – become one unit • Elimination reaction – opposite of addition • Substitution reaction – Exchange parts • Rearrangement reaction – bonds and atoms reorganize. 5.2 How organic reactions occur • Reaction mechanism - step by step transformation • Formation of products – bond breaking/making Bond breaking Homolytic Heterolytic Bond making Homogenic Heterogenic Reaction Radical Polar 5.3 Radical reactions • • • • See earlier notes: Initiation Propagation Termination • Note this involves single electron species. 5.4 Polar reactions: how they occur • Due to attractions between positive and negative charges. • Organic molecules are electrically neutral. • Bond polarity makes it reactive. Figure 5.1 page 140 Carbon bonded to another element Page 140 McMurry 6e. p.141 Interaction with solvents or lewis acids • Eg. Alcohol (textbook) – carboxylic acids. Polarizability • Eg., Carbon and Iodine (non polar, but reactive) • Why? – Changes in electron distribution. – Large atoms have loosely held electrons Polar reactions • The basics: • Electron rich react with electron poor – Bond formation – donation of electrons – Bond breaking – atom leaves with both e- General polar reaction Similar to Lewis acids and bases Nu:- and E+ used for bonds to carbon 5.5 Addition reaction Why alkenes and not alkanes What is the mechanism? 5.6 Curved arrow Mechanism • • Nu: (lone pr. or multiple bond) to an E+ Types of Nu:– Neutral or Negatively charged • Type of E+ – Neutral or Positively charged • Must follow octet rule Problems in text • Problem5.8 a (in class) • Problem 5.8 b,c (on your own) 5.7 Describing A reaction: Equilibria • • • • • • Please read pages 150-153. Summary: Equilbrium constant Thermodynamics (Go and Keq) Go versus G Go = Ho - TSo 5.8 Review of Bond dissociation • The energy required to break a given bond into two radical fragments when molecule is in the gas phase. • Purpose: It roughly gives Ho 5.9 Energy diagrams and Transition states. Reaction energy diagram for the reaction of Ethylene with HBr p. 156 Key terms • Transition state • Activation energy Transition state • Highest energy • Can not isolate • Bond breaking/bond formation shown. Reaction profiles 5.10 Describing a reaction: Intermediates • Reactions – One step – Two step Biological stuff (p.159)