Phosphorus molecule

The trapping of alkyl, alkoxyl and alkylthiyl radicals by trivalent phosphorus compounds, followed by either a-scission or p-scission of the ensuing phosphoranyl radical, is a powerful tool for preparation of new trivalent or pen-tavalent phosphorus compounds [59]. However, the products of these reactions strongly depend on the BDE of the bonds, which are either formed or cleaved. For example, the addition of phenyl radicals on a three-coordinate phosphorus molecule occurs irreversibly, while that of dimethylaminyl (Me2N ) or methyl radicals is reversible, the amount of subsequent P-scission (formation of compound C) depending on the nature of Z and R (Scheme 25). For tertiary alkyl radicals and stabilized alkyl radicals no addition is observed (Scheme 25) [63]. 

The strained hydrocarbon [1,1,1] propellane is of special interest because of the thermodynamic and kinetic ease of addition of free radicals (R ) to it. The resulting R-substituted [ 1.1.1]pent-1-yl radicals (Eq. 3, Scheme 26) have attracted attention because of their highly pyramidal structure and consequent potentially increased reactivity. R-substituted [1.1.1]pent-1-yl radicals have a propensity to bond to three-coordinate phosphorus that is greater than that of a primary alkyl radical and similar to that of phenyl radicals. They can add irreversibly to phosphines or alkylphosphinites to afford new alkylphosphonites or alkylphosphonates via radical chain processes (Scheme 26) [63]. The high propensity of a R-substituted [1.1.1] pent-1-yl radical to react with three-coordinate phosphorus molecules reflects its highly pyramidal structure, which is accompanied by the increased s-character of its SOMO orbital and the strength of the P-C bond in the intermediate phosphoranyl radical. 

There have been ab initio studies of the bonding for a series of imino and amino phosphorus molecules,15 and for the phosphonium ylides (8).14 The anion character of the ylidic carbon is intermediate between that of olefinic and substituted carbanions. Polarisation of the H3P group has a stabilising effect. The influence of the substituent X on the inversion of the carbanion and also the tendency of the molecule to dissociate to carbene and phosphine is also discussed.14 CNDO/S MO calculations on the... 

Explanation (mole level) When 1 mole of solid phosphorus molecules reacts with 6 moles of gaseous... 

Since the atomic mass of phosphorus is 31.0, the formula of phosphorus molecules in the vapor is P4. (4 atoms / molecule x 31.0 = 124)... 

JH Here ogam, both the diphosphoranc-typc system on the left and ihc anionic structures on the nghi are unknown in simple phosphorus molecules, hut S-Fm is known, so these are reasonable structures. 

A large number of phosphorus compounds possess P - O bond(s) as phosphate esters (e.g., DNA, RNA, ATP, phospholipids, etc.) and these phosphates play important roles in living systems. Unlike a P - O bond, a P - C bond constructs phosphorus molecules, which are relatively reduced molecules compared to compounds constructed with a P - O bond. Both of the two... 

On the Jahn-Teller Origin of the Phosphorus Molecule P4 Activation by One- and Two-Electron Reduction... 

To find such effective compounds in activation processes by reduction (or oxidation), it is necessary to study in detail these processes and the activation mechanism. This can be done on the basis of the quantum chemical calculations only, which reveal the effects that take place when the phosphorus molecule is changed. 

In this article for the simulation of the phosphorus molecule in coordinated states the quantum chemical calculations of P4 were carried out with values of charge q = 0, — 1, —2. Special attention is given to the instabilities of the electronic and nuclear subsystems with the possible reduction of symmetry, resulting in the breaking of the chemical bonds in the tetrahedral phosphorus molecule. Results are analyzed using vibronic theory. 

Calculations of the electronic structure of the phosphorus molecule were carried out by ab initio MO LCAO Hartree-Fock-Roothaan SCF method in the restricted (RHF), restricted-open (ROHF) or unrestricted Hartree-Fock (UHF)... 

Transformations of phosphines to difluorophosphoranes proceed with xenon difluoride under mild conditions and in high yields, and the phosphorus-hydrogen bond is stable chlorine atoms are replaced by fluorine in chlorine-phosphorus molecules, while triphenyl and trimethyldifluorophosphorane are isolated in 90-100% yield130-132. Reactions of compounds containing P—N, P—O and P—S bonds with xenon difluoride proceed by fragmentation or dimerization133 (Scheme 55). 

The explanation why such a complicated reaction as the slow oxidation of phosphorus appears to be unimolecular is one which has often been brought forward in similar cases. The slowest part of the process is a diffusion, either of oxygen molecules to the reaction surface, or of phosphorus molecules from the surface, or of the inhibiting molecules of phosphorus oxide from the surface. According to the theory of diffusion the rates will follow the unimolecular law. Since the vapour pressure of phosphorus is low at ordinary temperatures, the... 

Complexes of type A with phosphane are determined by the tr-donor bond of the phosphorus atom. On the contrary, the (d-d)n back donation of the phosphorus is poor, due to much lower x-acceptor ability, and the balance of electrons cannot take place within the phosphorus metal bond. With respect to 31P NMR the phosphorus molecule is deshielded, exhibiting a low-field shift for the i 1-coordinated P atom of about 30-60 ppm compared to the uncoordinated phosphane phosphorus. 

Here Lgam, both the diphiuphorune-iypc iyi tcm on the lefl unil ihc amonic sirut-lurc . on the nghi ure unknown in simpW phosphorus molecules, but SiFm is known, so these are reusonnhic siruciures. 

In the gas phase, phosphorus, unlike nitrogen, exists as a tetrahedral molecule (Fig. 164). The a bonds, in spite of their being bent, are apparently preferred to the tz bonds of a nitrogen-like configuration. The dissociation energy of the phosphorus molecule is small and the element accordingly much more reactive than nitrogen. 

At its boiling point (280°C) and at atmospheric pressure, phosphorus has a gas density of 2.7 g L. Under the same conditions, nitrogen has a gas density of 0.62 g How many atoms of phosphorus are there in one phosphorus molecule under these conditions ... 

Here ag.iin. boih the (lipho.sphor in( -lype. sy.stcm on the left ami ihc anionic. slruclurc.s on the right arc unknown in simple phosphorus molecules, but SiFui is known, so these arc reasonable structures. 

Some other elements exist as more complex molecules. One form of phosphorus molecules consists of four atoms, and sulfur exists as eight-atom molecules at ordinary temperatures and pressures. Molecules that contain two or more atoms are called polyatomic molecules (Figure 2-3). 

Table 20. Ligand-Ligand Distances for Some Oxofluoro and Oxochloro Phosphorus Molecules and Phosphazenes...

Table 3.4. Exact masses and elemental compositions of organic phosphorus molecules observed in the ...

Table 3.6. Exact masses, elemental compositions and hydrogen deficiencies of organic phosphorus molecules observed only in the Experimental Nutrient Removal wetland outflow. Reprinted from Llewelyn et al. (2002) with permission from the American Chemical Society.

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