Raman spectra of gaseous and solid N₂F₄

Abstract

The Raman spectrum of gaseous N2F4 at a pressure of 760 torr was recorded with a spectral slit width of 3 cm-l. Ten of the expected eleven fundamentals of the symmetric motions of both the gauche and trans isomers give rise to strongly polarized Raman lines. These new data require a reassignment of some of the fundamentals for both the C2 and C2h conformers. The Raman of the solid at 18K was also recorded. Both conformers were found in the solid even after annealing the sample for 9 hours at a temperature of 101.6K and 3 hours at a temperature of 106.8K. Bands attributable to the gauche isomer became more intense relative to those for the trans isomer after several hours of annealing.

Thermodynamic properties of tetrafluorohydrazine and the difluoroamino radical

“…13 The latter authors analyzed their results by assuming that only the gauche isomer of NzF4 was present. 20,22 For the present work, the fundamental frequencies of Durig and MacNameeZ0 were used. Furthermore, at room temperatures, the gas consists of an equilibrium mixture of the two forms even though there is still some uncertainty about the exact composition of this mix-tUre.14J7, 19,21 Fundamental vibrational frequencies for both the gauche and trans forms of N2F4 have been reported15J6*18v20 and the assignments of different investigators are in good agreement.…”

“…The minor differences that do exist have been discussed. 20,22 For the present work, the fundamental frequencies of Durig and MacNamee20 were used. Values measured from Using these fundamental frequencies, heat capacities, entropies and Gibbs free-energy functions for the temperature range 298-1000 K have been calculated for both gauche and trans N2F4.…”

Conformational Stability of Tetrafluorohydrazine, N2F4

“…The assignment of a second fundamental in the 700 cm -1 region for the gauche conformer requires the deletion of another band previously assigned to this conformer. ,, The obvious choice is the 242 cm -1 infrared band, which is probably the P branch of the ν 6 fundamental (252 cm -1 ) of the trans conformer. There may be some contribution from the overtone of the torsional mode to the 242 cm -1 infrared absorption.…”

“…c Calculated Raman intensities in Å 4 u -1 using the RHF/6-31G* basis set. d Observed frequencies taken from ref with some reassignments.…”

“…Clearly from the previous experimental and theoretical findings, there is no doubt about the existence of gauche and trans rotamers of N 2 F 4 , but the conformational stability has not yet been determined. Additionally, many different vibrational assignments have been proposed and several interpretations are contradictory . Additionally, the potential function governing the conformational interchange in N 2 F 4 has not been determined.…”