1. Intramolecular Bonding vs Intermolecular Forces/Interactions
Intra (3 types)
Inter (4 types)
Which is stronger (generally)?
Which determines state of matter?

2. London Dispersion Forces
alignment of instantaneous dipole moments/induced dipoles
all molecules have London
non-polar covalent have London only
short lived, weak

3. Dipole-Dipole Forces alignment of permanent dipoles
polar covalent molecules have both London and Dip-Dip
larger difference in electronegativity (Pauling scale), increase strength of dipole-dipole
as distance between two dipoles increases, strength of IM decreases
In gas phase, strength decreases at large V and low P

4. Can water H bond to HF? HCN? Can HCN H bond to itself?
H bonding
strongest of three IM forces we have discussed
Need H attached to O, N, F
We will call one molecule the H-donor; the other will be the H-acceptor
if you have both, you can H bond to yourself
Can water H bond to HF? HCN?
Can HCN H bond to itself?
Can acetone (CH3COCH3) H bond to H2O? To itself?

6. H Bonding/Water
1 molecule of H2O can engage in 4 H bonds

7. Large spaces in ice make solid water < dense than liquid (makes life in water possible)
Reflects hexagonal crystal structure of ice

8. Ion Dipole Interactions
Generally, strongest of the four
When an ion “talks to” dipole moment
Ex. Na+ (aq) or Cl- (aq)
Draw this interaction

9. Solvent Properties of Water (likes dissolve likes)
Can dissolve np, polar, ionic, and things that can H bond
Dissolves ionic compounds through ion-dipole forces
Dissolve many polar non-ionic compounds through H bonding or dipole-dipole
Dissolved non-polar gases through dipole-induced dipole interactions

11. What forces are present in
ane, ene, yne?
alcohols?
amines?
carboxylic acids?
aldehydes?
ketones?
ethers?

12. Which of the following has the strongest IM Forces?
C2H6 or C2H5Cl
C2H5Cl or C2H5OH
CH4 or C2H6

13. Chromatography HPLC, GLC, Paper, Column
Uses IM forces and solubility to separate components of mixture
Do this with two phases
Stationary Phase
medium you put the mixture on (filter paper)
Mobile Phase
put stationary phase in developing solvent.
As solvent moves along the stationary phase, create mobile phase.

14. Chromatography
Separation is based upon differences in solubility or attraction to mobile phase versus the stationary phase
If component is attracted to solvent, will move with mobile phase more than something that is attracted to stationary phase

15. Clarify Step 4
Least soluble in stationary phase/most soluble in mobile phase moves fastest

16. Paper Chromatography
Separation process = resolution

17. Retention/Retardation Factor
Rf = distance to center of spot (no units)
distance solvent front
Rf values indicate if component is more attracted to mobile phase or stationary phase-How?

20. Physical properties like bp, surface tension, viscosity, and Pvap depend on
Size of molecule, MM
Generally, as increase MM, increase the physical properties
bp gets harder (requires higher temp), higher surface tension and more viscous
Strength of IM forces (depends on type)

22. Both C5H12

25. Liquids form droplets because there is a net inward pull.
Surface Tension is the energy to “flatten” droplet, to overcome IM forces and increase surface area.
High surface tension is for stronger IM bonds.

26. Liquids with high surface tension have strong IM forces
Explains why bugs can walk on water but we cannot
Would you expect a higher surface tension for
Ether or Methanol
Methane or Ethane

27. Viscosity Measure of a liquids resistance to flow (thickness)
Influenced by
IM forces MM
Shape (long chains make more contact)
Temperature (hot oil flows more easily)
Which has greater viscosity?
Ethanol or methanol
Butane or octane
Butane or cyclobutane
Butane or chlorobutane

28. Vapor Pressure, Pvap

29. Trends in Vapor Pressure
Water (H2O) = 24 mm Hg
Ethanol (CH3CH2OH) = 65 mm Hg
Ether (CH3CH2OCH2CH3) = 545 mm Hg

30. Vapor Pressure affected by
Strength of IM forces
Size of molecule (MM)
Surface area
What about temperature?