1. REACH will present significant challenges to all of us
REACH will present significant challenges to all of us. There’s still much water to flow under the bridge before the detailed requirements of REACH are set in tablets of stone.
However, there is one thing we can anticipate and that is that REACH will demand much greater supply chain co-operation on the use of chemicals.
From the chemical manufacturer, through the formulator, to the product manufacturer to the final retailer we will all have to work together far more, understand each others challenges, languages and contribution to a mutual value chain.
Today we want to share with you some ideas about how such partnerships can work. We don’t offer a panacea, nor do we imagine that our relationship is necessarily representative of those that you in this room may have, but we feel much of the learning from our experience can be interpreted constructively in your supply chains.

2. Molecular orbital (MO) theory

3. NOTE: +/- signs show PHASES of waves, NOT CHARGES! A B B A A + B
An analogy between light waves and wave functions () used to describe electron waves from interacting atomic orbitals.
Amplitudes of wave functions added
NOTE: +/- signs show
PHASES of waves, NOT
CHARGES! A B
Amplitudes of wave functions subtracted. B A
A + B
A - B

4. A B In phase 1SA + 1SB = bonding MO 1S
Out of phase 1SA- 1SB = antibonding MO
*1S

6. Contours and energies of the bonding and antibonding molecular orbitals (MOs) in H2.
Axially symmetric
OUT OF PHASE
E-density = blue
IN PHASE
Axially symmetric
H Atomic orbitals
Molecular orbitals of H2

7. The MO diagram for H2
# ANTIBONDING e’s = 0
# BONDING e’s = 2

8. 2 H.
H:H

9. Moleculuar Orbital (MO) Theory
ANTBONDING
These two new orbitals have different energies. 
BONDING
The one that is lower in energy is called the bonding orbital,
The one higher in energy is called an antibonding orbital.

10. MO diagram for He2+ and He2
Energy
s*1s
s1s
s*1s
AO of He 1s
AO of He+ 1s
AO of He 1s
AO of He 1s
Energy
s1s
MO of He+
MO of He2
He2 bond order = 0
He2+ bond order = 1/2
He2 does not exist!

12. . . Bonding/antibonding combinations of the three p atomic orbitals x
Note that “z” is the
internuclear direction z z y y
Axial symmetry means  bond
Non-axial symmetry
means  bond
Bonding/antibonding combinations of the three p atomic orbitals

13. Relative MO energy levels for Period 2 homonuclear diatomic molecules.
without big 2s-2p repulsion
with big 2s-2p repulsion
MO energy levels for O2, F2, and Ne2
MO energy levels for B2, C2, and N2

14. E(2p)-E(2s):
N eV
O eV
F eV
For N:
“small” 2p/2s separation
“big” *(2s) / (2pz) repulsion

16. MO occupancy and molecular properties for B2 through Ne2
Bond order 1 2 3 2 1
MO occupancy and molecular properties for B2 through Ne2

17. Using MO Theory to Explain Bond Properties
PROBLEM:
As the following data show, removing an electron from N2 forms an ion with a weaker, longer bond than in the parent molecules, whereas the ion formed from O2 has a stronger, shorter bond:
Bond energy (kJ/mol)
Bond length (pm) N2
N2+ O2
O2+
945
110
498
841
623
112
121
Explain these facts with diagrams that show the sequence and occupancy of MOs.
N2 loses 2p bonding e O2 loses *2p antibonding e

18. Two non-bonding orbitals are the lone pairs on F
The MO diagram for HF s
Two non-bonding orbitals
are the lone pairs on F
seen in The Lewis structure
for HF
AO of H 1s s
Energy
Note the H1S
is less stable
than the F2P
AO of F 2p
2px
2py
MO of HF

19. The MO diagram for NO PARAMAGNETIC 1 unpaired e 2p Energy 2p
2pxy
s2pz
*2pxy
s*2pz
The MO diagram for NO
PARAMAGNETIC
1 unpaired e 2s
AO’s of N 2p 2s
AO’s of O 2p
Energy
Note AO’s of the more
electronegative O are
More stable than those
of N
s*2s
s2s
MO of NO