Phosphorus, thermodynamic data

The thermodynamic data presented in Table XYI are calculated for the temperature T=0K. Note that the entropy factor favors betaine decomposition via directions A and B at higher temperatures. The reactions of organoelement analogs of carbenes with phosphorus and arsenic ylides are yet poorly studied. The presented above results of calculations allow an optimistic prognosis about the possibility of developing a new method for the synthesis of elementaolefins R2E14=CH2 (E14 = Si, Ge, Sn) on the basis of these reactions. 

Phosphorus. Early reports on the aromaticity of phospholes (Scheme 52) were controversial.152 X-ray crystallographic data show that 1,2,5-triphenylphos-phole has a nonplanar phosphole ring, while NMR, chemical, and thermodynamical data account for delocalization. Low inversion barriers of the phosphorus atom compared to the saturated congeners suggest nljz conjugation.153 154... 

Provision of Thermodynamic Data for Gaseous PCI, and PC1, Ions Arising from Studies on Ionic Isomerism in Phosphorus (V) Chloride... 

Calculations based on the experimental conditions presented above are consistent with our observations. Modeling of the Stanford experiments ( ) represent a great improvement over past efforts although a quantitative match seems to require more stable KPOx species or lower electron affinities for POjj species (16). Thus, It appears that our assumed thermodynamic data will provide a qualitatively correct picture although much of It Is uncertain by more than 10 kcal/mole. We now apply our model to realistic MHD generator conditions In order to predict the role of phosphorus chemistry in channel conductivity. 

Thermodynamic Data of Formation. The standard enthalpy of formation of gaseous PH3, fH298 = 5.4 1.7 kJ/mol, was calculated from the heats of the explosive decomposition of PH3/SbH3 mixtures with white phosphorus as the reference state and is the recommended value different experimental values are given in Phosphor C, 1965, pp. 10/1. The experimentally determined value yields AfG29s=13.4 and AfHo=13.39 kJ/mol [27]. Calculations from molecular constants with standard methods yielded thermodynamic data of formation and the equilibrium constant for the formation of PH3 as an ideal gas the reference states used were crystalline a white phosphorus (0 to 195 K), crystalline p white phosphorus (195 to 317 K), the melt (317 to 1180 K), and an ideal P2 gas at higher temperatures. Selected results are as follows [28] ... 

Equilibrium constants given by [3] log(Kp/atm° )=-275/T+2.46 log T-4x10 T-3.74 for (1) and log(Kp/atm° )=(387 87)/T+0.272 log T+1.32x10 T for (4)). A comparison of the gas-phase equilibria (1) to (3) shows that, apart from H2, P4 is the mayor product expected thermodynamically up to ca. 1200 K. Above that temperature P2 becomes predominant, while phosphorus atoms are less abundant than P4 by a factor 10, even at 2000 K [1]. Thermodynamic data predict that PH3 is unstable at room temperature, and disposed to decompose into gaseous [1, extrapolation of figure 3] or solid P4 (white phosphorus) [3]. 

As mentioned above (see Scheme 1), three main directions of the decomposition of intermediates that formed are possible when phosphorus and arsenic ylides react with compounds bearing C=X bonds 5,6,19,63,64,88 (i) elimination of R3E15=X to form olefins (Wittig type reaction) (ii) retro-Wittig type decomposition and (iii) elimination of R3E15 and formation of three-membered cycles (Corey-Chaykovsky type reaction). According to the data of Erker and coworkers,12,13,51 under kinetic control, the reaction of phosphorus ylides with thiocarbonyl compounds also affords phosphines and thiiranes, whose further transformations lead to olefins and R3PS under thermodynamic control. 

L. D. Quin, 15C Nuclear Magnetic Resonance Spectral Data of Heterocyclic Phosphorus Compounds, Thermodynamic Research Center, College Station, Texas 1983. 

P (c, red). The exact thermodynamic status of the solid forms of phosphorus other than yellow has not yet been determined. The vapor pressure of red phosphorus was measured by Chapman1 and Troost and Hautefeuille1 and the latter calculated, from the difference in the temperature coefficients of the vapor pressures of the yellow and red forms, the heat of transition from yellow to red to be 4.2 at 700°. From the difference in the heats of combustion of the yellow and red forms of phosphorus, Giran1 found T=3.7. A more direct measurement of the heat of transition is that from the data of Giran1 on the heats of reaction of the two forms with bromine in carbon disulfide, (2 = 38.79 and 43.01 for the red and yellow forms, respectively. These data yield T=4.22. Giran1 found that the so-called violet or black phosphorus had a heat of reaction of 38.56 with bromine in carbon disulfide. Apparently this form is thermochemically identical with the red form. 

Quantitative data are sparse for phosphorus macrocycle complex stabilities. However, the broad thermodynamic principles that apply to nitrogen systems should apply to those of phosphorus. The macrocylic effect is the net effect of a number of factors, inter alia changes in entropy, enthalpy, pH, solvent effects, ring size, and conformation, that results... 

The thermodynamic measurements for nickel phosphides were recently summarised by Schlesinger [2002SCH] (in that reference, red phosphorus (V) was used as the standard state for phosphorus). Schlesinger concluded that the details of the Ni-P phase diagram remain controversial, and that the available data are insufficient to allow calculation of assessed thermodynamic values for any nickel phosphides. No values are selected in the present review. 

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