INFRARED SPECTRUM, MOLECULAR STRUCTURE, AND THERMODYNAMIC FUNCTIONS OF HYDROXYLAMINE

The absorption spectrum of pure hydroxylamine in the vapor and solid states was measured with a prism instrument in the range 1.5–25 µ. Except in one case the fundamental vibrations were clearly outlined and in some instances, particularly the 1115 cm−1 band, the fine structure was resolved well enough for a significant calculation of the rotational constants. From the latter it was possible to confirm, within fairly close limits, the probable structure of the hydroxylamine molecule, a nearly symmetric top of point group Cs. At least two of the bands appeared to be doubled owing, presumably, to existence of a mixture of cis-and trans-forms of the molecule. The O—H and N—H distances have nearly the same value as in water and ammonia respectively and the N—O distance is 1.46 Å.The thermodynamic functions of gaseous hydroxylamine were calculated using the observed fundamental frequencies; some uncertainty accrues from the torsional oscillation. The infrared spectrum of crystalline hydroxylamine hydrochloride was also studied.