P atom

This is better understood with a picture see figure B3.3.11. The discretized path-integral is isomorphic to the classical partition fiinction of a system of ring polymers each having P atoms. Each atom in a given ring corresponds to a different imaginary tune point p =. . . P. represents tire interatomic interactions... 

As another example, the 2s and 2p orbitals on the two N atoms of N2 can be formed into pairs of sp hybrids on each N atom plus a pair of p atomic orbitals on each N atom. The sp hybrids directed... 

Tyson, J. P. Atomic Spectrometry and Plow Injection Analysis A Synergic Gombination, Anal Chim. Acta 1988, 214, 57-75. 

The reactivity of the individual O—P insecticides is determined by the magnitude of the electrophilic character of the phosphoms atom, the strength of the bond P—X, and the steric effects of the substituents. The electrophilic nature of the central P atom is determined by the relative positions of the shared electron pairs, between atoms bonded to phosphoms, and is a function of the relative electronegativities of the two atoms in each bond (P, 2.1 O, 3.5 S, 2.5 N, 3.0 and C, 2.5). Therefore, it is clear that in phosphate esters (P=0) the phosphoms is much more electrophilic and these are more reactive than phosphorothioate esters (P=S). The latter generally are so stable as to be relatively unreactive with AChE. They owe their biological activity to m vivo oxidation by a microsomal oxidase, a reaction that takes place in insect gut and fat body tissues and in the mammalian Hver. A typical example is the oxidation of parathion (61) to paraoxon [311-45-5] (110). 

Reaction with triplet oxygen 0( P) atoms [17778-80-2] gives high yields of CO and chloroacetaldehyde [107-20-0], with smaller amounts of acetyl chloride [75-36-5], HCl, methane [74-82-8], and polymer. The rate of the gas-phase reaction of vinyl chloride with 0( P) atoms has also been reported (41). 

FIGURE 18.14 With NMR spectroscopy one can observe the metabolism of a living subject in real time. These NMR spectra show the changes in ATP, creadne-P (phosphocre-adne), and P levels in the forearm muscle of a human subjected to 19 minutes of exercise. Note that the three P atoms of ATP a, /3, and y) have different chemical shifts, reflecting their different chemical environments. 

Me3C6H2-). By contrast, B(PEt2>3 is a dimer with a planar B2P2 ring of 4-coordinate B and P atoms (124).d o) planar 4-membered ring of 3-coordinate planar B and pyramidal P atoms is featured in the diphos-phadiboretane MesPB(tmp) 2 (125) (tmp =... 

Gep2 is formed as a volatile white solid (mp 110°) by the action of Gep4 on powdered Ge at 150-300° it has a unique structure in which trigonal pyramidal [GePsI units share 2 P atoms to form infinite spiral chains (Pig. 10.2). Pale-yellow GeCl2 can be prepared similarly at 300° or by thermal decomposition of GeHCls at 70°. Typical reactions are summarized in the scheme ... 

Turning finally to compounds with bonds from the heavier Group 14 elements to heavier Group 15 elements we may note compounds such as [Sn C(PMe2)3)2] which has the pseudo trigonal bipyramidal structure (6). This complex, which has Sn bonded exclusively to four P atoms, is formed as yellow crystals by the... 

C), and is much less reactive it is therefore safer and easier to handle, and is essentially non-toxic. The amorphous material can be transformed into various crystalline red modifications by suitable heat treatment, as summarized on the right hand side of Fig. 12.3. It seems likely that all are highly polymeric and contain three-dimensional networks formed by breaking one P-P bond in each P4 tetrahedron and then linking the remaining P4 units into chains or rings of P atoms each of which is pyramidal and 3 coordinate as shown schematically below ... 

MP (M = Cr, Mn, Fe, Co, Ru, W) distorted trigonal prismatie eoordination of P by M plus two rather short eontaets to P atoms in adjaeent trigonal prisms, thus building up a eontinuous ehain of P atoms NiP is a distortion of this in whieh the P atoms are grouped in pairs rather than in ehains (or isolated as in VP). 

As seen from Fig. 12.15 the structure of a-P4S4 resembles that of AS4S4 (p. 579) rather than N4S4 (p. 723). The 4 P atoms are in tetrahedral array and the 4 S atoms form a slightly distorted square. The 2 P-P bonds are long (as also in P4S3... 

It follows from these structural principles that each P atom is 5-covalent. However, the oxidation state of P is 5 only when it is directly bound to 4 O atoms the oxidation state is reduced by 1 each time a P-OH is replaced by a P-P bond and by 2 each time a P-OH is replaced by... 

There has been much confusion over the structure of these compounds but their diamagnetism has long ruled out a monomeric formulation, H2PO3. In fact, as shown in Table 12.7, isomeric forms are known (a) hypophosphoric acid and hypophosphates in which both P atoms are identical and there is a direct P-P bond (h) isohypophosphoric acid and isohypophos-phates in which 1 P has a direct P-H bond... 

The structure of isohypophosphoric acid and its salts can be deduced from nmr which shows the presence of 2 different 4-coordinate P atoms, the absence of a P-P bond and the presence of a P-H group (also confirmed by Raman spectroscopy). It is made by the careful hydrolysis of PCI3 with the stoichiometric amounts of phosphoric acid and water at 50° ... 

Figure 12.22 Structures of (aj (Cl PNMe) , and (b) jCl(S)PNMc 2- Note the difference in length of the axial P-N and equatorial P-N bonds (and of the axial and equatorial P-Cl bonds) about the trigonal bipyramidal P atoms in (a).

An X-ray crystal structure of the Pr N-derivative shows the presence of a bent, 2-coordinate P atom, equal P- N distances, and accurately planar 3-coordinaie N atoms as in (c) above.In liquid ammonia ammonolysis also occurs ... 

Figure 12.31 Schematic representation of the molecular structure of [P(C3HMes)(02C2H4)Ph] showing the rectangular-based pyramidal disposition of the 5 atoms bonded to P the P atom is 44 pm above the C2O2 plane.

Fig. A. Molecular-orbital representation of the 1-centrc F-Xe-F bond, (a) The possible combinations of colinear p, atomic orbitals, and (b) the energies of the resulting MOs (schematic).

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