Phosphorus lead halides

When this type of reaction was applied to the preparation of the ester 2, phosphorus trichloride was used as the phosphorus (III) halide. Treatment of this with one mole equivalent of 3,3-dimethoxyprop-l-ene yields mainly the enol ether 4, with smaller amounts of the isomeric a-chloroallyl methyl ether 5. This mixture is not very stable and has to be treated with trimethyl phosphite rapidly, in order to provide 2 in good yield, as shown in Scheme 1. The significance of this sequence is that it reveals that since 2 is the only product, the reactions leading to 2 via 4 must proceed by two allylic inversions, whilst those via 5 involve direct substitution twice at the original acetal carbon. 

It was McCormack who, in 1953, in the patent literature, first reported the cycloaddition of phosphorus(III) halides to l,3-dienes . As then represented, the sequence took the form depicted in reaction 13 (X = Cl or Br). The careful addition of water to the crystalline 1 1 adduct, formulated as a halogenophosphonium salt (92), gave the unsaturated phosphinic chloride (93, R = Br or Cl) or acid (93, R = OH). Since the original publication of the procedure, the application of modern spectroscopic techniques has demonstrated that the final products in such reactions are mixtures of the 3-phospholene (93) and 2-phospholene (94) isomers, conveniently represented, when admixed and in unknown proportions, as 95. It has since become apparent that the relative proportions of the isomeric forms 93 and 94 of any derivative depend on the nature of the halogen X and on the manner of work-up thus, in an acidic work-up medium, the products tend to have the structure 94, but neutralization during the hydrolysis step leads to derivatives of the isomeric 93. The reaction consists simply in mixing the reactants at room temperature and... 

The amminolysis of phosphorus (V) halides leads to a class of inorganic materials known as phosphazenes which are characterized by the repeating (R2P=N) unit. The presence of two elements active in flame retardancy (phosphorus, nitrogen) which may behave in a synergistic manner makes phosphazenes particularly attractive in this important application. 

Lead dioxide Aluminum carbide, hydrogen peroxide, hydrogen sulfide, hydroxylamine, ni-troalkanes, nitrogen compounds, nonmetal halides, peroxoformic acid, phosphorus, phosphorus trichloride, potassium, sulfur, sulfur dioxide, sulfides, tungsten, zirconium... 

Another general method for converting alcohols to halides involves reactions with halides of certain nonmetallic elements. Thionyl chloride, phosphorus trichloride, and phosphorus tribromide are the most common examples of this group of reagents. These reagents are suitable for alcohols that are neither acid sensitive nor prone to structural rearrangement. The reaction of alcohols with thionyl chloride initially results in the formation of a chlorosulfite ester. There are two mechanisms by which the chlorosulfite can be converted to a chloride. In aprotic nucleophilic solvents, such as dioxane, solvent participation can lead to overall retention of configuration.7... 

In a similar vein, the keto bridge in 5 can be replaced by oxygen with retention of activity. Reduction of acetophenone derivative 19 by means of sodium borohydride leads to the corresponding alcohol (20). Reaction with phosphorus tribromide with cyanide gives... 

A variety of leaving groups (other than simple halide) may be associated with the electrophilic component of the reaction with these phosphorus components. These include haloepoxides (leading to (3-ketophosphoryl compounds),59 quaternary ammonium salts,60-64... 

In the instances of phosphorous and phosphonous acid systems, the generation of a new C-P bond via the classical Michaelis-Arbuzov reactions as noted above leads to products that are esters themselves. Isolation of the free acid product requires cleavage of the ester linkage in a separate reaction step, generally after isolation and purification of the initial product. The advent of silyl phosphorus reagents for the Michaelis-Arbuzov reaction allowed free acid products to be isolated simply by water workup of the reaction system. Further, since the byproduct was a silyl-halide, the general concern that the by-product halide would participate in an extraneous Michaelis-Arbuzov reaction was obviated. 

The mechanism for the reactions with phosphorus halides can be illustrated using phosphorus tribromide. Initial reaction between the alcohol and phosphorus tribromide leads to a trialkyl phosphite ester by successive displacements of bromide. The reaction stops at this stage if it is run in the presence of an amine which neutralizes the hydrogen bromide that is formed.9 If the hydrogen bromide is not neutralized the phosphite ester is protonated and each alkyl group is successively converted to the halide by nucleophilic substitution by bromide ion. The driving force for cleavage of the C—O bond is the... 

To date, however, only few reactions between phosphine and a non-metal halide, in which a chemical bond is formed between phosphorus and a non-metal by HCl condensation, are known. To these, apart from the above-mentioned reactions, belongs also the reaction with CF3SCI which, depending upon the chosen proportions of the reactants, in a sealed tube at -95 °C leads to the formation of (CF3S)2PH or (CF3S)3P Both compounds are not very stable thermally and decompose at 40-50 °C. Tris(trifluoromethylthio)-phosphine forms an unstable adduct with chlorine, which decomposes at 0 °C to give a mixture of PCI3, bis(trifluoromethyl)-disulphide and trifluoromethyl-sulphenyl chloride. 

Phosphorus halides react with alcohols to yield alkyl halides at low temperature (0 °C). Primary and secondary alcohols undergo Sn2 reactions with PX3. This type of reaction does not lead to rearranged products, and does not work well with 3° alcohols. PI3 has to be generated in situ via reaction of iodine and phosphorus. 

Studies of the formation, chemical composition, and properties of deposits have shown that they consist of partially oxidized organic material, including more or less nitrogen, sulfur, and phosphorus. Compounds of iron, silicon, calcium, and other metals are present in small quantity, together with substantial amounts of lead oxides, sulfates, and halides from combustion of the antiknock fluid. The effects of these deposits are both physical and chemical in nature they may physically interfere with lubrication, heat transfer, gas flow, operation of valves and spark plugs chemically, they may bring about corrosion and oxidation. 

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