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 Bond making Reaction 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.

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 Summary: Equilbrium constant Thermodynamics (  G o and Keq)  G o versus  G  Go =  H o - T  S o

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  H o

5.9 Energy diagrams and Transition states. p. 156 Reaction energy diagram for the reaction of Ethylene with HBr

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)