Methods phosphorus

Phosphorus and Silicon in Waters, Effluents and Sludges [e.g. Phosphorus in Waters, Effluents and Sludges by Spectrophotometry-phosphomolybdenum blue method. Phosphorus in Waters and Acidic Digests by Spectrophotometry-phosphovanadomolybdate method. Ion Chromatographic Methods for the Determination of Phosphorus Compound, Pretreatment Methods for Phosphorus Determinations, Determination of silicon by Spectrophotometric Determination of Molybdate Reactive Silicon-1 -amino-2-naphthol-4, sulphonic acid (ANSA) or Metol reduction methods or ascorbic acid reduction method. Pretreatment Methods to Convert Other Eorms of Silicon to Soluble Molybdate Reactive Silicon, Determination of Phosphorus and Silicon Emission Spectrophotometry], 1992... 

The preparation of fluonnated acid anhydrides can be done by simple methods Phosphorus pentoxide removes a molecular equivalent of water from tnfluoroacetic acid and tnfluoromethanesulfonic acid and forms the mixed anhydride [Si] (equation 53)... 

The process used by Kunckel and Boyle gives slight yield and phosphorous was an expensive product in their day. Only after Gahn or Scheele (about 1771) had shown that bones contain phosphoric acid, was discovered the process in which the syrupy liquid produced by removing a great part of the calcium by nitric or sulphuric acid is reduced by ignition with carbon. By this method phosphorus was obtained at a cost which removed it from the class of expensive rarities, and gave it wide industrial possibilities. 

Preparative Methods phosphorus trichloride is allowed to react sequentially with alkylmagnesium chloride, methylmagnesium bromide, and BH3-THF complex in THF to give... 

Kudzin. Z.H.. Kotynski. A., and Andrijewski, G., Aminoalkanediphosphonic acids. The synthesis via thioureidoalkanephosphonate method. Phosphorus, Sulfur Silicon Relat. Elem., 77, 208, 1993. 

Al, Si, P Digestion with diethyl ether-concentrated sulphuric acid-potassium persulphate. Silicon determined gravimetrically. Aluminium determined by titrimetric EDTA method. Phosphorus determined by spectrophotometric molybdenum blue method. 

In larhon surface science XRF and EDX are mainly used to determine the inorganic constituents of carbons which cither exist there as a result of activation method (phosphorus in phosphoric acid activated carbon), are present in the precursor [282], or are deposited on the surface as a product of surface reactions [78]. Quantitatively determination of the content of elements in carbon using XRF is not an easy task. Using solid as a matrix requires special calibration precautions such as high and uniform dispersion of the target element, uniform particle sizes of the matrix, the constant volume of the matrix, etc. [283]. Moreover, very often special filters liave to be used to separate, for instance sulfur signal fiom that of phosphorus. 

Non-radioactive elements can be converted into radioactive isotopes by neutron bombardment in a reactor, cyclotron or van de Graaff generator they can then be detected by radiometric methods. Phosphorus-, sulphur- and chlorine-containing compounds for example, have been detected on paper chromatograms in this way. In order to determine traces of a compound quantitatively, known amounts of it are irradiated on the same chromatogram. 

In modified methods, phosphorus pentoxide is rendered soluble by derivatizing it with a TMS group, resulting in polyphosphates. Trimethylsilyl polyphosphate (TMS-PP) has been employed to prepare l-cyano-6-methoxy-benzonorbornadiene in 91% yield from the corresponding carboxamide [1087]. 

It is however more complicated, esters of phosphorous acid being also formed (c/. p. 308). Iodides are usually prepared by a modification of this method, the ethanol being mixed with red phosphorus, and iodine added. The phosphorus iodide is thus formed in situ, and at once reacts with ethanol to give the corres ponding iodide. 

This is a modification of Method 5, iodine being added to a mixture of red phosphorus and ethanol phosphorus tri- iodide is thus formed m situ, and readily reacts with the ethanol, giving ethyl iodide and phosphorous acid (p. 96). 

One of the general methods for the preparation of acid chlorides is the action of phosphorus pentachloride on the corresponding carboxylic acid ... 

One disadvantage of this method is that it is sometimes difficult to separate the acid chloride sharply from the phosphorus oxychloride by fractional dis tillation, and unless the boiling oints of these two substances are fairly wide apart, traces of the oxychloride will occasionally pass over in the vapour of the acid chloride. If, however, thionyl chloride is used instead of phosphorus... 

This method of sulphonamide Tormation may obviously be invalidated by the presence of nuclear —NHj or —OH groups, which could react with ihe phosphorus pentachloride or with the subsequent —SO Cl group. 

Method 2. Mix 1 0 g. of 3 5-dinitrobenzoic acid with 1 5 g. of phosphorus pentachloride in a small, dry test-tube. Warm the mixture gently over a small smoky fiame to start the reaction when the reaction has subsided (but not before), boil for 1-2 minutes or until the solid matter has dissolved. Pour the mixture while still liquid on a dry watch glass (CAUTION the fumes are irritating to the eyes). When the product has solidified, remove the liquid by-product (phosphorus oxychloride) by transferring the pasty mixture to a pad of several thicknesses of filter paper or to a small piece of porous tile. Spread the material until the liquid has been absorbed and the residual solid is dry. Transfer the 3 5 dinitrobenzoyl chloride to a test-tube, add 0-5-1 ml. of the alcohol, and continue as in Method 1. 

The melting points of these esters are usually much lower than those of the corresponding 3 5 dinitrobenzoates their preparation, therefore, offers no advantages over the latter except for alcohols of high molecular weight and for polyhydroxy compounds. The reagent is, however, cheaper than 3 5 dinitrobenzoyl chloride it hydrolyses in the air so that it should either be stored under light petroleum or be prepared from the acid, when required, by the thionyl chloride or phosphorus pentachloride method. 

Method 1. Use the apparatus depicted iu Fig. Ill, 56, 1, but omit the thermometer also attach a cotton wool (or calcium chloride) tube to the side arm of the filter fiask receiver in order to prevent the entrance of moisture into the apparatus. Mount the reaction fiask in a water bath e.g., a large beaker or other convenient vessel). It is important that all the apparatus be perfectly dry, since both phosphorus trichloride and acetyl chloride are decomposed by water. The set-up should be assembled in the fume eupboard. 

Trimethylene dibromide (Section 111,35) is easily prepared from commercial trimethj lene glycol, whilst hexamethylene dibromide (1 O dibromohexane) is obtained by the red P - Br reaction upon the glycol 1 6-hexanediol is prepared by the reduction of diethyl adipate (sodium and alcohol lithium aluminium hydride or copper-chromium oxide and hydrogen under pressure). Penta-methylene dibromide (1 5-dibromopentane) is readily produced by the red P-Brj method from the commercially available 1 5 pentanediol or tetra-hydropyran (Section 111,37). Pentamethylene dibromide is also formed by the action of phosphorus pentabromide upon benzoyl piperidine (I) (from benzoyl chloride and piperidine) ... 

The procedure is not usually applicable to aminosulphonic acids owing to the interaction between the amino group and the phosphorus pentachloride. If, however, the chlorosulphonic acid is prepared by diazotisation and treatment with a solution of cuprous chloride in hydrochloric acid, the crystalline chlorosulphonamide and chlorosulphonanilide may be obtained in the usual way. With some compounds, the amino group may be protected by acetylation. Sulphonic acids derived from a phenol or naphthol cannot be converted into the sulphonyl chlorides by the phosphorus pentachloride method. 

It is believed that the red phosphorus is the true reducing agent and the iodine (or iodide) functions as a hydrogen carrier. This proc ure replaces the obsolete method of heating with red phosphorus and concentrated hydriodic acid in a sealed tube. 

Method 2. Place 90 g. of sodium benzenesulphonate (Section IV,29) (previously dried at 130-140° for 3 hours) and 50 g. of powdered phosphorus pentachloride (1) in a 500 ml. round-bottomed flask furnished with a reflux condenser heat the mixture in an oil bath at 170-180° for 12-15 hours. Every 3 hours remove the flask from the oil bath, allow to cool for 15-20 minutes, stopper and shake thoroughly until the mass becomes pasty. At the end of the heating period, allow the reaction mixture to cool. Pour on to 1 kilo of crushed ice. Extract the crude benzenesulphonyl chloride with 150 ml. of carbon tetrachloride and the aqueous layer with 75 ml. of the same solvent. Remove the solvent under atmospheric pressure and proceed as in Method 1. The yield is about 170 g., but depends upon the purity of the original sodium benzenesulphonate. 

White phosphorus may be made by several methods. By one process, tri-calcium phosphate, the essential ingredient of phosphate rock, is heated in the presence of carbon and silica in an electric furnace or fuel-fired furnace. Elementary phosphorus is liberated as vapor and may be collected under phosphoric acid, an important compound in making super-phosphate fertilizers. 

METHOD 2 [113]-Phenol can be oxidized with either performic, formic or acetic acids to catechol. For example phenol, formic acid, concentrated H2O2 and polyphosphoric acid are heated 2 hours at 80 C to give 53% catechoi. Addition of phosphorus pen-toxide (P2O5) is said to increase the yieid. 

The most suitable synthetic method for these products is the heterocyc-lization reaction of N-thioacyl derivatives of amino acids (202) with phosphorus tribromide (378, 442-450, 559, 560) or anhydrous trifluoroacetic acid (448, 449, 451, 452) (Scheme 103). Treatment of N-thioacyl amino acids with acetic anhydride leads directly to the thiazolylacetate without isolation of an intermediate thiazolinone (365. 452). 2-Alkoxy-derivatives of A-2-thiazoline-5-one, however, can be obtained without acetylation by this method (453, 454). 

The O-S exchange method in presence of a-halogenated carbonyl compound is a very good one for thiazole compounds. The thioamide is prepared in situ by the action of amide upon phosphorus pentasulphide with solvent. The a-halogenated aldehyde reacts directly. But the O-Se exchange cannot be performed with a-halogenated carbonyl compounds because of the apparition of phosphoric acid. (Scheme 3), The C-Se bond is very sensitive to add pH. 

Another method, due to V an Dormael (57) involves heating acelamidoethanoi with phosphorus pentaselenide (Scheme 57),... 

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