Phosphorus compounds, oxidation

Electroless coatings form by the reduction of nickel ions by hypophosphite (usually monobasic sodium hypophosphite, NaH2P02>. The treating solution contains an excess of nickel. Rates of precipitation depend on temperature and pH, and control of these variables allows control of the properties of the coating, in particular its phosphorus content [144]. The oxidized phosphorus compound releases hydrogen ions, which tend to reduce the pH of the solution. The formulation therefore usually contains acetate or citrate buffers. 

Flame retardants antimony oxide, phosphorus compounds, halogenated compounds, antoxidants... 

On concentrating the solution, a solid of formula As40jq. SH O (which may be composed by hydrated arsenic(V) acid) is obtained, and this, on fairly prolonged heating to 800 K, loses water and leaves arsenic(V) oxide. No compounds corresponding to the other acids of phosphorus are formed, but salts are known. 

Prolonged oxidation of any phosphorus compound, followed by standing in water, converts it to phosphate(V). This can then be detected by the formation of a yellow precipitate when heated with... 

Organophosphorus Derivatives. Neopentyl glycol treated with pyridine and phosphorus trichloride in anhydrous dioxane yields the cycHc hydrogen phosphite, 5,5-dimethyl-l,3-dioxaphosphorinane 2-oxide (2) (32,33). Compounds of this type maybe useful as flameproofing plasticizers, stabilizers, synthetic lubricants, oil additives, pesticides, or intermediates for the preparation of other organophosphoms compounds (see Flame retardants Phosphorus compounds). 

Phosphorus. Eighty-five percent of the phosphoms, the second most abundant element in the human body, is located in bones and teeth (24,35). Whereas there is constant exchange of calcium and phosphoms between bones and blood, there is very Httle turnover in teeth (25). The Ca P ratio in bones is constant at about 2 1. Every tissue and cell contains phosphoms, generally as a salt or ester of mono-, di-, or tribasic phosphoric acid, as phosphoHpids, or as phosphorylated sugars (24). Phosphoms is involved in a large number and wide variety of metaboHc functions. Examples are carbohydrate metaboHsm (36,37), adenosine triphosphate (ATP) from fatty acid metaboHsm (38), and oxidative phosphorylation (36,39). Common food sources rich in phosphoms are Hsted in Table 5 (see also Phosphorus compounds). 

Phosphorus compounds exhibit an enormous variety of chemical and physical properties as a result of the wide range ia the oxidation states and coordination numbers for the phosphoms atom. The most commonly encountered phosphoms compounds are the oxide, haUde, sulfide, hydride, nitrogen, metal, and organic derivatives, all of which are of iadustrial importance. The hahde, hydride, and metal derivatives, and to a lesser extent the oxides and sulfides, are reactive iatermediates for forming phosphoms bonds with other elements. Phosphoms-containing compounds represented about 6—7% of the compound hstiugs ia Chemical Abstracts as of 1993 (1). 

Although unsynunetrically substituted amines are chiral, the configuration is not stable because of rapid inversion at nitrogen. The activation energy for pyramidal inversion at phosphorus is much higher than at nitrogen, and many optically active phosphines have been prepared. The barrier to inversion is usually in the range of 30-3S kcal/mol so that enantiomerically pure phosphines are stable at room temperature but racemize by inversion at elevated tempeiatuies. Asymmetrically substituted tetracoordinate phosphorus compounds such as phosphonium salts and phosphine oxides are also chiral. Scheme 2.1 includes some examples of chiral phosphorus compounds. 

A comparison of bromine and phosphorus compounds on the flammability of PET fiber shows phosphorus (as phosphine oxide) to be 3.7 times more effective than bromine (Table 1). No synergy was observed. Nevertheless, phosphorus was shown to be more effective than antimony normally used as a synergist, resulting in a higher oxygen index at a lower concentration (Table 2). 

Nitrogen analogs are known for some of these phosphorus compounds, but they are less stable because the resonance is lacking. For example, amine oxides, analogs of... 

SET reactions involving phosphoniumyl radicals have been developed by Yasui et al. [41,55], particularly for the dediazoniation of arenediazonium salts [56] (Scheme 20) and for the oxidation of trivalent phosphorus compounds [41,57] (Scheme 21). 

Three- and pentacoordinate organic phosphorus compounds can be oxidized through a free radical Arbuzov reaction, i.e., formation and p-scission of a phosphoranyl radical (Scheme 24). The P-scission is regioselective homolysis occurs on a ligand located in an equatorial site. Both a- and P-scissions are strongly dependent on the strength (bond dissociation energy) of the cleaved... 

Phosphorus compounds occur widely in nature, with some of the most common forms being phosphate rocks and minerals, bones, and teeth. Phosphate minerals include calcium phosphate, Ca3(P04)2 apatite, Ca5(P04)30H fluoroapatite, Ca5(P04)3F and chloroapatite, Ca5(P04)3Cl. Elemental phosphorus was first obtained by H. Brand, and its name is derived from two Greek words meaning "light" and "I bear" because of the phosphorescence of white phosphorus due to slow oxidation. 

Photo-oxidation was seen as a possible route to a total phosphorus method. Again, early work on the method was done by Armstrong et al. [15] and Armstrong and Tibbitts [36]. Grasshoff [37] adapted the method to continuous automatic analysis a variation on this method is considered the standard method for automatic analysis today [18]. Bikbulatov [38], on the other hand, feels that such important phosphorus compounds as ATP and DI are not completely decomposed by ultraviolet irradiation and that persulfate oxidation gives better results. 

Typically, intense chemiluminescence in the UV/Vis spectral region requires highly exothermic reactions such as atomic or radical recombinations (e.g., S + S + M - S2 + M) or reactions of reduced species such as hydrogen atoms, olefins, and certain sulfur and phosphorus compounds with strong oxidants such as ozone, fluorine, and chlorine dioxide. Here we review the chemistry and applications of some of the most intense chemiluminescent reactions having either demonstrated or anticipated analytical utility. 

Neodymium Nickel Phosphorus Aluminum, aluminum(III) chloride, ethylene, 1,4-dioxan, hydrogen, methanol, nonmetals, oxidants, sulfur compounds... 

The cyclopolyphosphines that were used to prepare the carbene-phosphinidene complexes described earlier were formed by the reduction of higher oxidation state phosphorus compounds, typically di-chlorophosphines, RPC12 (47-49). However, in some cases a separate reduction step is not necessary and it is possible to prepare the car-bene-phosphinidene complex (74) directly by reaction of a stable nucleophilic carbene with RPC12 (44). 

Quite often, we find nonsystematic nomenclature used in the literature dealing with organophosphorus compounds. This results in unnecessary confusion, as systematic nomenclature is easy to use and understand. Nomenclature based on the oxidation state of the phosphorus center eliminates the confusion and helps to promote understanding of the chemistry as well as to facilitate communication. Table 1.1 shows structures for tricoordinate and tetracoordinate phosphorus compounds related to oxyacids with their English general names. Also noted are the names for simple esters of the parent acids. They are organized based on oxidation state and the number of bonds of the carbon-phosphorus type. 

Phosphorus compounds, 19 19-73 bond properties of, 19 26 chemical properties of, 19 20-31 chiral-centered, 19 25-26 economic aspects of, 19 67-69 as flame retardants, 19 51 inorganic, 11 487-488 oxidation states, coordination numbers, and geometries of, 19 20-26 as oxyacid derivatives, 19 20 reactive organic, 11 496 497 titanium in, 25 56-57 triply connected, 19 25 U.S. prices of, 19 68t U.S. production of, 19 67t... 

Vanadium is beneficial and possibly essential for humans. It is certainly essential for a number of organisms. Vanadate (oxidation state V) and its derivatives are phosphate analogues, showing both ground state and transition state analogy (both structural and electronic) with phosphorus compounds. The analogy of five-coordinate vanadium compounds with the transition state of phosphate ester hydrolysis is well documented, and explains why so many vanadium compounds are potent inhibitors of phosphatases, ribonucleases and ATPases. 

Just as O.M.P.A. is oxidized enzymically to a cholinesterase inhibitor of greatly enhanced activity (p. 173), so also are systox (p. 179), thimet and certain related sulphur organo-phosphorus compounds. 

The oxidation of mixtures of PBN and Nu- by TBPA + in HFP gave no spin adducts from the commonly used nucleophiles (Table 10), except in the case of triethyl phosphite and related phosphorus compounds (Eberson et al., 1996a). Thus any PBN + formed must react so slowly with Nu that the spin adduct concentration is too low to be detectable. Titration of the percentage HFP in dichloromethane which just barely allowed for the formation of the... 

Compared with peroxysulfur compounds, very few peroxyphosphorus compounds are reported. Phosphorus peroxide derivatives have been postulated as possible intermediates in certain biological transformations, although they have never been isolated in such systems . Monoperoxyphosphonic acid can be prepared in situ and applied for some common oxidation reactions ". Only one example of phosphorus peroxide, i.e. bis(phenylphosphinyl) peroxide, has been studied . It is believed that when trivalent phosphorus compounds are allowed to react with ozone and a source of singlet oxygen, phosphorus ozonides 54 are obtained (equation 89). ... 

Trivalent phosphorus compounds are more readily oxidized than the corresponding nitrogen derivatives on account of their higher nucleophilicity however, the oxidation of such highly reactive substrates by dioxiranes has been sparsely studied. Only about a handful of examples are available in the literature, such that little may be said about the general trends in reactivity and selectivity. 

As a potential class of compounds we came to consider phosphine oxides, reasoning that pentavalent phosphorus compounds are certain not to interact strongly with Ru. 

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