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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.
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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 breakingBond makingReaction Homolytic Homogenic Radical Heterolytic Heterogenic 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.
Carbon bonded to another element Page 140 McMurry 6e.
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
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.
5.10 Describing a reaction:Intermediates • Reactions • One step • Two step