The Raman Spectra and Molecular Constants of Phosphorus Trifluoride and Phosphine

Abstract

The Raman frequencies of PF₃(l) were found to be ω₁(1), 890 cm^‐1; ω₂(1), 531 cm^‐1; ω₃(2), 840 cm^‐1; and ω₄(2), 486 cm^‐1, indicating a regular pyramid structure of the molecule. Three frequencies were observed for PH₃(l): 2306 cm^‐1, 1115 cm^‐1 and 979 cm^‐1. With the aid of electron diffraction data the standard virtual entropies of PF₃(g), PCl₃(g), AsF₃(g), and AsCl₃(g) at 25°C are calculated to be 64.2, 74.7, 69.2, and 78.2 cal./deg., respectively; that of PH₃(g) is estimated to be 50.5 cal./deg. These data lead to the following free energies of formation at 25°C: AsCl₃(g), ‐62,075 cal.; PH₃(g), 2750 cal.; PCl₃(g), ‐62,220 cal.