Phosphorus groups

Phosphor-gehalt, m. phosphorus content, -geruch, m. phosphorus odor, -geschoss, n. phosphorus bullet, incendiary bullet, -gruppe, /. phosphorus group, -guano, m. phosphatic guano. 

The bonding of the phosphorus group to the aromatic ring of PS is an important element of these groups, which creates a higher resistance capability to fire [17-21]. The conversion of PS into its peroxide form... 

Studies on the formation and reactivity of P-centered radicals continue to be a versatile source of mechanistic information and reactions of interest in synthetic chemistry. Various new persistent or stable P-centered radicals have been described and could find applications as paramagnetic probes. The possibility of influencing the properties of organic free radicals bearing an appropriately located phosphorus group should find interesting applications. 

The extent of restricted rotation about the amide band of (38) was used to compare the electron-withdrawing process of phosphonium salts (38, Y = alkyl) and chalcogenides (38, Y = O or S) with the more conventional electron-withdrawing groups. These phosphorus groups were found to exert a — A7 effect comparable with that of a nitro-group. 

Most of the methods of synthesis reported above present some limitations and constraints lack of solubility for polycationic phosphorus-containing dendrimers from generation 3 [2], dendrimers of weak molecular weight [4], difficulties to overcome cross Unking reactions [6], possibility only to incorporate phosphorus groups on the surface of dendrimers [3], etc. 

Fig. 6. Dendrimers of generation 5 with 96 various terminal phosphorus groups...

At this stage two strategies (one of them outlined in Scheme 37) can be developed to start the construction of dendrimers within the cascade structure of 88-[G3]. Each of them allows the synthesis of six internal dendrimers of generation 4 into the internal voids of 88- [G3]. 31P NMR constitutes an extraordinary and unique tool for monitoring the construction of these controlled polydendritic structures (see Fig. 9 for illustration). Chemical shifts of phosphorus groups are different from one generation to another and the intensities of signals are of... 

Various bifunctional potentially hemilabile ligands (72) bearing phosphorus groups were prepared and their coordination to rhodium was studied. Their effect on the hydroformylation of styrene was assessed.237... 

Cristau, H.J., Vors, J.P, Beziat, Y., Niangoran, C., and Cristol, H., Umpolung of a,p-ethylenic ketones and aldehydes by phosphorus groups, in Phosphorus Chemistry, Proceedings of the 1981 International Conference, Quin, L.D. and Verkade, J.G., Eds., American Chemical Society, Washington, D.C., 1981, p. 59. 

Perhaps the first successful variation of the PPFA framework was the development of the JosiPhos family of ligands (33) [125, 131, 141, 142], Here, the two phosphorus groups are attached to the same cyclopentenyl ring rather than one to each of the rings. The C2-symmetry model is now a distant memory for these ligand families. 

Eq. 2.79. Rearrangement reaction of zirconacycles containing an alkynyl phosphorus group. 

The migration of a C=C bond to form a C=N bond was also observed with hydro-xylamine [78, 79], hydrazine [80, 81] and primary amines [82]. The /f iminylphos-phine oxide formed in the reaction may serve as a Wittig reagent in the presence of a base to react with a ketone or an aldehyde leading to ,/fun saturated alkenyl-imines 153 (Scheme 10.74). The phosphorus group can be a phosphonium salt as well as a phosphonate. 

Aromatic substituent effects due to phosphorus groups have been studied for a number of reactions.47 Thus ester hydrolysis and fluoride-displacement rates, for (56) and (57) respectively, are enhanced by phosphorus substituents (X = O or ), while the rate of hydrolysis of the halide (58) is enhanced for X = , but slowed for X = O.47 A perturbation M.O. analysis of these observations has been presented.48... 

The main feature for cation recognition by tetra-bridged phosphorylated cavitands arises from the cooperative effect of the four phosphorus groups and the aromatic molecular cavity. In the phosphorus(IV) cavitands guest binding will be achieved through O (P=0) or S (P=S) coordination with different affinity for hard or soft metal ions. On the other hand, transition metal rim complexes described above can act as host for metal cation. 

Unhke silanol groups, acidic P-OH groups cannot self-condense in solution, which discards the formation of P-O-P bonding. The formation of frameworks including phosphorus groups involves P-O-Metal hnkages (as in... 

When Roscoe investigated them he found that vanadium is a tri- and pentavalent element of the phosphorus group. He also discovered that what Berzelius had taken for the metal was really the mononitride, VN, and that most of the vanadium compounds studied by the Swedish chemists had contained oxygen. 

Another important biochemical compound derived from adenine is adenosine triphosphate (ATP). ATP plays a critical role in supplying energy in organisms to support metabolism. ATP is a nucleotide similar to RNA. In ATP the base is adenine and the phosphorus group is a three-phosphoryl (P032 ) chain. 

Cristau et a/.41 reported an electrochemical deprotection of y-thioacetalated phos-phonium salts which involves the elimination of the base of the phosphorus group. The reaction scheme is represented by reaction 19. This conversion proceeds through an... 

Bicyclic bridged phosphorinane derivatives can be synthesized by different methods. When phenylphosphine is heated with cycloocta-2,7-dienone to 135 °C in the presence of polymerization inhibitors, e.g. hydroquinone, and the double Michael addition product is oxidized, the two crystalline syn and anti isomers (total yield 48-59%) are isolated. Separation by crystallization gives the pure compounds which can in turn be transformed at the carbonyl or the phosphorus group (equation 10) (75T33,76JOC589). 

In a preceding section we saw crystallographic evidence that substitution of phosphorus ligands for carbon monoxide in Cr(C0)6 leads to a strengthening of Cr—C bonds, particularly those trans to the phosphorus groups, and this was interpreted in... 

NUCLEOSIDE. A compound of importance in physiological and medical research, obtained during partial decomposition (hydrolysis) of nucleic acids and containing a purine, oi pyrimidine base linked to either tf-ribose, forming ribosides, or rf-deoxyribose, forming deoxynbosides. They are nucleotides minus the phosphorus group. See also Adenosine and Nucleic Acids... 

The second paper230 investigated the stereochemistry at phosphorus. The pyramidal nature of the phosphorus group was confirmed, with an inversion barrier of ca. 19 kJ mol-1, slightly greater than in PH3. The barriers for inversion in directly-bonded three-co-ordinate atoms is determined principally by the differences in electronegativity of the atoms.231... 

In contrast with all of the other groups described in this chapter, the majority of the structures for the phosphorus-group xanthates are in fact binary xanthates. There are four discernable structural motifs for these compounds, but all are... 

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