Bonding

• what does increasing nuclear charge do on energy levels?

  lowers the energy of all orbitals
• Describe the bonding between C and O:

  • Electron density is unevenly distributed, more of the electron density resides on the more electronegative element (O)
  • The orbital coefficient in the bonding MO is larger on O
  • conversely, the orbital coefficient in the antibonding is large on C
• what are the requirements for a strong overlap?

  • Good energy match between interacting orbitals
  • Overlap efficiently (eg same size)
  • Correct symmetry
• what is a homo?

  Highest occupied molecular orbital
• what is a Lumo?


  lowest unoccupied molecular orbital
• How to tell which give the best energy match?

  closest in energy of homo and lumo
• what in the bonding interation nucleophiles?

  homo
• what is the bonding interaction of LUMOs?


  electrophile
• what do curly arrows represent?

  the movement of a pair of electrons from a filled orbital (HOMO) to an empty orbital (LUMO)
• what happens to charge in a reaction?


  cannot be created or destroyed
• Nucleophiles: donate an electron to an electrophile to form a chemical bond in a reaction. All molecules with a free pair of electron or at least one pi bond can act as nucleophiles.
• Order of nucleophile ability:

  1. negative charge on atom
  2. Lone pair
  3. Pi bond
  4. sigma bond
• How to draw a nucleophile mechanism for pi bond?

  arrow from centre of C=C bond through carbon making the new bond to electrophile
• How to draw a nucleophile mechanism for a sigma bond?

  Arrow through centre of B-H through the hydrogen atom making the new bond to electrophile
• Electrophiles: accept an electron pair from a nucleophile to form a chemical bond in a reaction. All molecules with either a full or partial positive charge, or those have an atom which does not have an octet of electrons can act as a electrophile
• Order of electrophilic ability:

  1. empty orbital
  2. Pi bond
  3. sigma bond