Nature of Phosphorus(V) Chloride in Ionizing and Nonionizing Solvents

Document Type

Article

Publication Date

1973

Publication Source

Journal of the American Chemical Society

Abstract

Laser Raman spectra in conjunction with freezing point depression measurements provide evidence for two competing equilibria in the ionizing solvents CHICN, CH3N02, and C6H5N02, (1) 2PC15 8 PC14+ + PCl6- and (2) PCls s PC14+ + C1-, with (1) being predominant above about 0.03 m and (2) being predominant at lower concentrations. These observations resolve earlier conflicting reports on the ionization scheme in acetonitrile and nitrobenzene. The nature of phosphorus(V) chloride has also been studied in nonionizing solvents. When cryoscopic data are treated in the usual manner (neglect of possible solid solution formation) the apparent molecular weight in C6H6 supports the monomeric formulation PC15, while in CCl, the apparent molecular weight supports the dimeric formulation P2C110. This study has shown, however, that solid solution formation does occur in the carbon tetrachloride-phosphorus(V) chloride system and that it cannot be neglected. Application of the experimentally determined coefficient for the distribution of solute between solid and liquid phases (mole fraction of solute in solid phase :mole fraction of solute in liquid phase = 0.50 + 0.02 at infinite dilution) to correct for solid solution formation gives an apparent molecular weight which is in excellent agreement with monomeric PCls.

Inclusive pages

1474–1479

ISBN/ISSN

0002-7863

Publisher

American Chemical Society

Volume

95

Peer Reviewed

yes

Issue

5

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