The Raman Spectra and Molecular Constants of Phosphorus Trifluoride and Phosphine

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.