Phosphorus compounds, mass spectra

J.10 (a) White phosphorus, which has the formula P4, burns in air to form compound A, in which the mass percentage of phosphorus is 43.64%, with the remainder oxygen. The mass spectrum of A yields a molar mass of 283.9 g-mol. Write the molecular formula of compound A. (b) Compound A reacts with water to form compound B, which turns litmus red and has a mass percentage composition of 3.087% 11 and 31.60%... 

Alkylphosphines have been studied (99, 231), as have cyclopolyphos-phines (120). The reaction products of phosphorus with various olefins were investigated using mass spectral methods (108), and a large number of phospholines have been reported (181, 237). The mass spectrum of the trimer of tetramethylphosphinoborine showed that B—P, C—B, and C—P bonds were broken first, and with the pentamer of the dimethyl compound, B—H, B—P, and C—P bonds were broken (101, 232). The spectra of thiophosphorustri-A -methylimide and its arsenic analog were reported by Holmes and Forstner (130). Ionization potentials have been recorded for many perfluoroalkylarsines and some of the related alkyl compounds (79). 

Analysis of A found C, 13.8% H, 2.1% P, 21.3% F, 39.2% and Rh, 23.6%. The mass spectrum of A showed a highest mass peak at m/z = 436. When compound A was heated to 60°C it was converted initially into an isomeric derivative B which subsequently formed a third isomer C. The H n.m.r. spectra of compounds A, B and C, measured at room temperature, are listed in the table. These spectra can be assigned by taking into account proton-proton and proton-rhodium couplings [l( " Rh) natural abundance of Rh isotope is 100%], proton-phosphorus couplings are not observed under these conditions. Interpret these data as fully as you can. Deduce the molecular structures of the complexes A, B and C and suggest a mechanism for the isomerization. 

Both compounds crystallize with the cadmium diiodide structure (space group P3ml) as previously reported on polycrystalline samples.3 For platinum disulfide, ao = 3.542(1) A and c0 = 5.043(1) A, and for platinum ditelluride, a0 = 4.023(1) A and c0 = 5.220(3) A. Direct chemical analysis for the component elements was not carried out. Instead, precision density and unit-cell determinations were performed to characterize the samples. The densities of both compounds as determined by a hydrostatic technique with heptadecafluorodeca-hydro-l-(trifluoromethyl)naphthalene as the density fluid4 indicated that they are slightly deficient in platinum. For platinum disulfide, = 7.86 g/cm3 and Pmeas = 7.7(1) gm/cm3, and for platinum ditelluride, p = 10.2 gm/cm3 and Pmeas = 9.8(1) gm/cm3. In a typical experiment an emission spectrum of the platinum disulfide showed that phosphorus was present in less than 5 ppm. A mass spectroscopic examination of the platinum ditelluride revealed a small doping by sulfur (less than 0.4%) and traces of chlorine and phosphorus (less than 100 ppm). 

Conversions in pentane proceed in an nonuniform manner at high temperatures. In addition to unidentified products exhibiting different 31P NMR AX patterns, as well as the main product dichlorophosphane and another unknown substance, which exhibits a 31P NMR shift of + 301 ppm, one obtains a red compound, of which elemental analysis and the molecular mass point to the trimer phosphathioketene. The number of isomer compounds of this composition is limited by the 31P NMR spectrum. The A2X system, of which the X triplet is split into a double doublet if detected in solution in chloroform, indicates two acyclic PC double bonds and one phosphorus atom as a ring member (117). A possible explanation is given in Fig. 22. This could be in agreement with the addition of a monomer to the dimer, forming the six-membered ring compound with the proposed structure. 

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