ABSTRACT
The kinetic stability of molecular oxygen The standard redox potential of the oxygen couple (02/H20) is very positive (+0.82 V) and hence the reaction of most materials with oxygen takes with a large release of energy. Fortunately for life on earth, the oxygen molecule is very stable and at room temperature is relatively inert, otherwise little free oxygen would exist in the biosphere . The kinetic barrier preventing the reaction of molecular oxy gen with most other compounds arises from its electronic structure . It might be assumed at first sight that molecular oxygen would have a simple covalent double-bond structure 0 = 0. This valence bond arrangement would seem to satisfy the pairing of the six outer electrons of the two individual atoms:
However, the oxygen molecule shows magnetic properties , indicating the presence of two unpaired electrons , not at all obvious from the simple valence arrangement shown above. The reason for the presence of unpaired electrons can be seen from an examination of the molecular orbitals of the molecule (Figure 6 . 1 ) . When the atomic orbitals at the 2p level hybridise , the resulting molecular orbitals arrange such that the IT* orbital is ala lower energy than the a* orbital.
