The Infra-Red Spectrum of Hydrogen Peroxide

The absorption spectrum of hydrogen peroxide vapor was examined under low dispersion in the range 2–15μ. Four bands were observed at 3590, 2630, 1255, and 877 cm−1. The spectrum of the liquid also was measured between 2 and 21μ; it showed five bands at about 3400, 2780, 1350, 880, and 550 cm−1. The last one, which seems very diffuse, is presumably the torsional oscillation of the OH groups; as such it corresponds to a potential energy barrier of the order of 4 kcal./mole. New assignments are proposed in agreement with the model of Penney and Sutherland. Under high dispersion the second harmonic O–H frequency was found to consist of two identical hybrid bands at 7036.6 and 7041.8 cm−1, of which the rotational constant for the ground state is in perfect agreement with that already found for the third harmonic band. The explanation given previously for the doublet character of the vibrational levels of hydrogen peroxide is further substantiated by the present results. From both vibrational and rotational data the O–H distance in hydrogen peroxide appears to be slightly greater than that in water.