1. Intermolecular Interactions

2. Types of Interactions Two main categories (but subtleties in both)
Charged
Van der Waals (London Dispersion Forces)

3. Charged Interactions Non-charged Fully charged Partially charged
Basically based on Coulomb’s Law
Non-charged
Alkanes, oil, benzene
Fully charged
Salt, ammonium (not ammonia)
Partially charged
Polar, dipoles

4. Other Electric Considerations
Electric fields
Induction
Electric field “displaces” charges
Polarizability
How easy induction happens

5. Polarity Can be strong or weak Stems from molecular features
Strong – water, acids
Weak – alcohols, esters
Stems from molecular features
Double/Triple bonds
Nitriles
Presence of oxygens and nitrogens
Ethylene is non polar, a ketone is polar
Acidic hydrogens
Acids
Aromaticity
Diminishes polarity
A nitrogen in an aromatic ring is less polar
Pi-Pi stacking

6. Hydrogen-Bonding Subcomponent of polarity Acceptors Donors
If not somewhat polar, they can’t H-bond
Acceptors
Ketones
Donors
Amines
Acceptor/Donors
Acids
Relative strengths (like polarity)

7. London Dispersion Forces
Hard sphere
Repulsions
Billiard balls
“Touching” is favorable
Better the contact, the more attractive
Lennard-Jones – example potential

8. VDW Contacts All about how much/well molecules touch
Basically, how they pack
Size (big v. small)
Shape (bent, linear, planar, etc…)

9. Let’s characterize
Acetonitrile

10. Let’s characterize
Toluene

11. Let’s characterize
Acetone

12. Let’s characterize
CO2