Structure and Properties
... and in the solid (crystalline) phase.H2O2 adopts a nonplanar structure of C2 symmetry. Although chiral, the molecule undergoes rapid racemization. The flat shape of the anti conformer would minimize steric repulsions, the 90° torsion angle of the syn conformer would optimize mixing between the filled p-type orbital of the oxygen (one of the lone pairs) and the LUMO of the vicinal O-H bond. The observed anticlinal "skewed" shape is a compromise between the two conformers.
Although the O−O bond is a single bond, the molecule has a relatively high barrier to rotation, of 29.45 kJ/mol; the rotational barrier is 12.5 kJ/mol for the bulkier molecule ethane. The increased barrier is ascribed to repulsion between nonbonding electrons (lone pairs) on the adjacent oxygen centres. The bond angles are affected by hydrogen bonding, which is relevant to the difference between the structure of gaseous and crystalline forms; indeed a wide range of values is seen in crystals containing H2O2.
Read more about this topic: Hydrogen Peroxide
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