Phosphorus-containing groups

All the above structures contain the P—C—O—B fragment. Among boryloxyalkylphosphines and their derivatives with an exocyclic phosphorus containing group, (123)—(125) are reported (92IZV196). Such compounds were obtained from secondary phosphines, aromatic aide-... 

Figure 2). -Diketones 35 and j5-ketoesters 36-38 are commonly used as CH-acidic ketones 24. Cyanoketones 39 and 40, nitroketones 41, as weU as ketones substituted with beteroaromatic 42, sulfur-containing 43, and phosphorus-containing groups 44 and 45 are also favored (Figure 2). Syntheses... 

The introduction of a phosphorus-containing group into the side chain of the hydrazone fragment of isatin was reported in [97]. The results of a study of the kinetic relationships and mechanism of the addition of dialkyl phosphites to substituted benzylideneamines, which were related to the basicity of the initial amines, were published as abstracts in [98]. 

J.R. Ebdon, D. Price, B.J. Hunt, P. Joseph, F. Gao, G.J. Milnes, and K.L. Cunhffe, Flame retardance in some polystyrenes and poly(methyl methacrylate)s with covalently bound phosphorus-containing groups Initial screening experiments and some laser pyrolysis mechanistic studies. Polym. Degrad. Stab., 69, 267-277 (2000). 

Banks, M., Ebdon, J. R., and Johnson, M., Influence of covalently bound phosphorus-containing groups on the flammability of poly(vinyl alcohol), poly(ethylene-co-vinyl alcohol) and low-density polyethylene, Polymer, 1993, 34, 4547 1556. 

Lecithin is a complex mixture of materials see Section 4. The structure above shows phosphatidylcholine, the principal component of egg lecithin, in its a-form. In the jl-form, the phosphorus-containing group and the R group exchange positions. 

Despite wide variations of synthesis conditions, the treatment of cellulose with dimethylphosphite, monomethylphosphite and phosphorous acid failed to yield phosphites containing only one type of phosphorus-containing groups. This difficulty was overcome by using phosphoric anhydrides as the esterifying reagents. The action of mixed anhydrides of phosphorous acids and acetic acid on cellulose has yielded cellulose esters with alkyl-(methyl-)phosphorous acid (73) ... 

Transferases Catalyze the transfer of carbon-, nitrogen-, or phosphorus-containing groups... 

Epoxy resins modified with polysiloxane containing organophosphorus and epoxide groups Pendant cyclic phosphorus containing groups LOI and cone calorimetry performed to evaluate flame retardancy [26]... 

Table 12.1 Various phosphorus-containing groups discussed in this chapter.

Phosphorus is known as an effective char promoter. Charring limits the release of fuels to the flame and therefore reduces the heat released. Moreover, the char accumulates on the surface of the material and can act as a protective layer which limits the heat transfer from the flame to the condensed phase and the gas transfer from the pyrolysis zone to the flame. This phenomenon is called the barrier effect. Nevertheless, it should be noted that the presence of char is not a sufficient condition to observe an effective barrier effect. Its structure (cohesion, porosity, thickness) is also veiy important but rarely studied. Thermal stability is another important parameter to assess the reaction to fire of a material. Indeed, the higher is the degradation temperature of a polymer, the greater is the heat required to start its pyrolysis. Table 12.2 lists the effects of phosphorus-containing groups on the thermal stability and charring for a variety of polymers. 

Table 12.3 Contributions of some phosphorus-containing groups.

Finally, Vahahi et al. calculated the contributions of the phosphonate group for two chemically modified PMMAs. Significant differences were found between both molecular structures. This result confirms that the contributions of phosphorus-containing groups could hardly be calculated while their effects depend on their chemical environment. 

Vinyl and allyl phosphonates can be used as comonomers in addition polymers. Also, modifications of polymers with phosphorus-containing groups, such as phosphorylation of polyvinyl alcohol, leads to improvements in flame retardancy compared to the polymers themselves. Phosphorus-containing acrylates have adhesive properties as well as FR ones. Acrylates containing phosphonic acid groups have some interesting and encouraging properties. 

NUCLEOSIDASES AND RELATED ENZYMES - TRANSFERRING A PHOSPHORUS-CONTAINING GROUP-KINASES... 

Introducing phosphorus-containing groups in the substrate has also proved to be a flexible and efficient procedure for controlling the regio- and stereoselectivity of the reaction. Thus, homoallylic alcohols have been transformed into homoallylic phosphites, and the influence of the coordinating heteroatom on the regio- and stereoselectivity of cyclohexenyl derivatives has been studied [53]. 

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