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❏Resonance → molecule represented by more than one lewis structure but differing in
only placement of electron.
❏Resonance is not the true structure because it is not in chemical equilibrium, it does not
fluctuate. Therefore the true structure is the resonance hybrid.
❏Resonance structures used because Lewis structures is localized therefore resonance
❏Resonance hybrid has lower potential energy therefore more stable.
❏Rules for drawing resonance:
❏Only move multiple bonds and lone pairs. NOT single bonds.
❏Atom position stays the same.
❏Proper lewis structure (no pentavalent carbon)
❏Charge conservation -- sum of formal charges must be the same.
❏Receptor of electron pairs are positive charged atoms, EN atom, or atom with multiple
❏Drawing resonance for cation → One arrow changed at a time. Electron pair moves
towards the positive formal charge.
❏Drawing resonance for anion → Move two arrows at a time. Electron pair moves away
from negative charge. Note: Atom to bond, bond to atom.
❏Negative charge is most favoured on the most EN atom.
❏When there is a positive charge remaining, the positive charge is favoured on the
resonance with full octet.
❏Charge separation (when compound is neutral breaks to positive and negative). It is not
Types of Chemical Reactions
1. Acid-Base Reactions (Proton Transfer)
2. Substitution Reaction → One element replaces another
3. Elimination Reaction → Removal of two elements to form alkene
4. Addition Reaction → Addition of two elements to break alkene bond
5. Rearrangement (catalyst) → change in carbon skeleton
6. Oxidation (w/ [O] as catalyst) → remove Hydrogen to form water
7. Reduction (catalyst) → Addition of Hydrogen; Example Ketone → Alcohol.
❏Homolytic cleavage (homolysis) → Electron pair splits, each atom takes its own
electrons (half arrows).
❏Heterolytic Cleavage (heterolysis) → One atom takes all and an ion is formed.
❏Bronsted-Lowry Acid → Donates proton.
❏Bronsted-Lowry Base → Accepts proton. Base has a lone pair of electrons to accept
Organic Reaction Notes
❏As pKa increases, the acid becomes weaker.