³¹P nuclear magnetic resonance chemical shifts of elemental phosphorus in the gas phase

Abstract

The N.M.R. signals of phosphorus vapour, relative to liquid white phosphorus, have been measured in the temperature and vapour pressure ranges of 253 to 295~ and 440 to 990 mm of Hg. A linear relationship with a gradient of -3"3 • 10-3 p.p.m./mm of Hg was found between the chemical shift of the vapour, relative to orthophosphoric acid, and the vapour pressure. Extrapolation to zero vapour pressure gives a value of 553"1 p.p.m, for the chemical shift of the isolated phosphorus molecule. The predicted gas phase chemical shift at zero pressure is found to be ll-0p.p.m, to higher field than this extrapolated shift. A qualitative discussion about solvent effects indicates that this difference originates from the diamagnetic component of the shielding changes caused by the repulsive overlap forces. The spin-lattice relaxation time of phosphorus vapour in the investigated temperature range is estimated to be /> 5 ms.

Reaction field model with free volume for the NMR chemical shift of129Xe dissolved in organic solvents

“…Eqs. (11) and (12) also predict the slope to be negative as has been previously observed [8,19,25,[38][39][40]. Deviations from linearity have been observed for methanol [38,39], elemental liquid phosphorous [40], and solid xenon [12].…”

31P N.M.R. studies of the gas phase and solvent chemical shifts of phosphorus tribromide

“…In order to calculate 8 from 8 P, the temperature dependence of the line position of liquid PBra, relative to orthophosphoric acid, was measured. As recently determined experimentally [1], the shielding change of the phosphorus atom in HaPO 4 between 40 and 211~ causes, at most, an upfield shift of 0-2 p.p.m. with increasing temperature.…”

“…Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions In a previous report the gas-to-liquid downfield chemical shift of white phosphorus was found to have the unusually large value of 93-0 p.p.m. [1]. Also, very large solvent effects have been observed for white phosphorus [2,3].…”

“…The gas-to-infinite dilution chemical shifts of elemental phosphorus, measured to date, lie within a range of 41-3 p.p.m. [1]. In the present work the gas-to-liquid shift and the chemical shifts of dilute solutions of phosphorus tribromide are given and compared with the corresponding shifts of white phosphorus.…”

“…The gas phase signals were obtained by summing between 36 and 144 scans using a Fabri-Tek FT-1062 time averaging computer. The experimental procedures for the determination of 8 p were the same as those we have described recently for nuclear magnetic resonance studies of the vapour of elemental phosphorus [1]. The vapour pressure over PBr a in the temperature range employed was obtained as a mean from two slightly different empirical vapour pressure-temperature relations [4].…”