Studies of Hydrogen Peroxide: The Infrared Spectrum and the Internal Rotation Problem

Several hydrogen peroxide infrared absorption bands have been obtained under 0.2 cm—1 resolution. They demonstrate both doubling due to internal rotation and effects due to the inertial asymmetry. The ground-state rotational constants are found to be: A″=10.068 cm—1, B″=0.8740, C″=0.8384. These parameters indicate a wide dihedral angle for H2O2, as proposed in the following structure: OO bond=1.475 A, OH bond=0.950 A, dihedral angle=119.8°, and OOH angle=94.8°. The constants are applied to the microwave data for H2O2 and the deuterated species. The ground-state splitting is found to be 11.44 cm—1, and this, used with the recently reported torsion at 317 cm—1, yields the barriers hindering internal rotation. They are Vcis=1300 cm—1 and Vtrans=300 cm—1. A simple correlation of the infrared doublings is attempted.