Boiling Points and Intermolecular Forces - Exercise 33
Exercise 1.33 - Boiling Points and Intermolecular Forces
Introduction
In this video, Exercise 1.33 is discussed, focusing on arranging compounds in order of increasing boiling points. The goal is to determine the order based on intermolecular forces such as hydrogen bonds, dipole-dipole interactions, and London dispersion forces.
Main Points
- Identifying Hydrogen Bonds:
- Molecules with N, O, F, or Cl bonded to H can form hydrogen bonds.
- Out of the given molecules, only two can form one hydrogen bond each.
- Dipole-Dipole Interactions:
- Molecules with N, O, F, or Cl bonded to something other than H can form dipole-dipole interactions.
- Again, only two molecules can form one dipole-dipole interaction each.
- London Dispersion Forces:
- Count the number of significant atoms (C and O) to determine the strength of London dispersion forces.
- More atoms mean more London dispersion forces.
- The molecule with seven significant atoms has the highest boiling point due to stronger London dispersion forces.
- Ranking the Molecules:
- The molecule with the most atoms has the highest boiling point.
- Next is the molecule with significant intermolecular forces.
- For the remaining molecules, count branching to determine the next highest boiling points:
- Least branching leads to stronger London dispersion forces and a higher boiling point.
- More branching leads to fewer London dispersion forces and a lower boiling point.Conclusion
By analyzing intermolecular forces, we can rank molecules by their boiling points. Hydrogen bonds and dipole-dipole interactions are crucial, but when these tie, the number of atoms and branching help determine the boiling points.