Modified method of preparation

Chatt, J. et al., J. Chem. Soc., Dalton Trans., 1985, 1131-1136 A modified method of preparation from ethylene, phosphorus trichloride and phosphorus in a stainless autoclave gives a highly pyrophoric reaction residue. 

A modified method of preparation from ethylene, phosphorus trichloride and phosphorus in a stainless autoclave gives a highly pyrophoric reaction residue. 

Blue perchromates, which are referred to the second type, R HjCrO, or R CrOs.HjOa, are formed by the interaction at a low temperature of 30 per cent, hydrogen peroxide with acid solutions of chromates a modified method of preparation consists in the neutralisation of a cooled blue ethereal solution of perchromic acid by an alcoholic solution of the alkali. Similar to the red salts, the crystalline blue perchroniates are unstable in the moist condition they are even more so than the red variety, but both forms may best be preserved by keeping in an atmosphere saturated with aqueous vapour. ... 

Methods of preparation of the laminates depend on the partieular grade of polyimide resin used but in one process the polyimide precursor is dissolved in acetone and this solution is used to impregnate the glass or carbon fibre and thus produce a pre-preg . The pre-preg is dried and then pre-cured at about 200°C for about 3 hours. This operation reduces the volatile content and also modifies the flow properties to make them more suitable for the subsequent... 

Although not so generally applicable for the preparation of dicyclopentadienyl metal compounds as the sodium cyclopenta-dienide method, the amine procedure represents the simplest preparation of ferrocene. The amine procedure can also be employed for dicyclopentadienylnickel (about 80% yield), using nickel bromide obtained by the action of bromine on nickel metal powder and 1,2-dimethoxyethane as the solvent. The method of preparation given here is a modified version of that originally described. ... 

The precipitation of casein in its uncombincd form by the addition to milk of one or another acid, forms the basis of all methods of preparation. These differ widely, however, in the subsequent purification. In the method of Hammarsten,4 just enough alkali is added to dissolve this casein completely. The alkalinity reached in this process somewhat modifies its physical properties but probably not its composition. In the method of Van Slyke and Bosworth 5 the last trace of calcium is removed by adding oxalate to an ammoniacal solution of the casein, but... 

Since the possibility of direct melt intercalation was first demonstrated [11], melt intercalation has become a method of preparation of the intercalated polymer/ layered silicate nanocomposites (PLSNCs). This process involves annealing, statically or under shear, a mixture of the polymer and organically modified layered fillers (OMLFs) above the softening point of the polymer. During annealing, the polymer chains diffused from the bulk polymer melt into the nano-galleries between the layered fillers. 

The requirement of small structural differences within the series of reactants for obtaining a LFER has its parallel in series of catalysts. Meaningful values of result only when the catalysts operate principally in the same way, that is, when the reaction mechanism is basically the same. This is most likely to occur when the catalysts differ only by minor modifications in the method of preparation or when their composition is only slightly modified by the addition of promoters. With chemically different catalysts the similarity is achieved when the active centers have as their decisive component a common species, for example, protons on solid acidic catalysts. 

The synthesis of the four monocarboxylic acids of dibenzothiophene has been recorded in the previous review. However, several modified preparations have since been described. Ethyl 1-dibenzothiophene-carboxylate has been synthesized from 2-allylbenzo[6]thiophene (Section IV,B, 1) hydrolysis afforded the 1-acid (57% overall). In a similar manner, 3-methyl-1-dibenzothiophenecarboxylic acid was obtained from the appropriately substituted allyl compound. This method is now the preferred way of introducing a carbon-containing substituent into the 1-position of dibenzothiophene. 2-Dibenzothiophenecarboxylic acid has been prepared by oxidation of the corresponding aldehyde or by sodium hypoiodite oxidation of the corresponding acetyl compound. Reaction of 2-acetyldibenzothiophene with anhydrous pyridine and iodine yields the acetyl pyridinium salt (132) (92%), hydrolysis of which yields the 2-acid (85%). The same sequence has been carried out on 2-acetyldibenzothiophene 5,5-dioxide. The most efficient method of preparing the 2-acid is via carbonation of 2-lithio-... 

The method of preparation and physical properties of the alkyl azides used in the study are also presented in Table 2.1. The alkyl bromide and sodium azide in aq MeOH is denoted as A and aq EtOH and sodium azide is denoted as B. 1,2-Diazidobenzene and 1,4-diazidobenzene were synthesized using the process shown in Fig. 2.10. 1-Azidonorborniane was synthesized according to a modified literature procedure shown in Fig. 2.11. 

Patent Number EP 823443 A2 19980211 FOAMED PARTICLES OF MODIFIED POLYPROPYLENE RESIN AND METHOD OF PREPARING SAME... 

Method of enzyme modification. The method of preparation of the organic solvent-soluble enzyme called modified lipase (J) is presented below ... 

Research Focus Method of preparing surface adhesives using phenolic resins either modified with disulfides or free radically copolymerized with ethane-dithol and then postreacted with epichlorohydrin. 

Efforts have been made by many research workers in the past to modify or suppress the phase-transition of AN by phase stabilizing it with the help of some suitable chemical compounds induced in the AN lattice or by modifying its properties with the application of surfactants, or by changing the method of preparation of AN itself in order to make it acceptable for use in propellant formulations. 

The general route outlined below, follows the modified method of Williams [48] used his preparation of the gem-dimethyl dioxepin ring of PHB. By this method we were able to prepare the four dioxepin-ring anaologs in which the geminal methyl groups at C26 of MFA were replaced by a cyclobutyl 67a, cyclohexyl 67b, diethyl 67c, and ethyl-methyl 67d groups [Fig. (20)]. 

The preparation Of iodine dioxide.—N. A. E. Millon s method of preparation by the reduction of iodic acid, modified by M. M. P. Muir, is as follows ... 

The described procedure is based on the methods of Johnson and Ambler 3 and Anderson et al.,4 as modified by Ulbricht and Price.5 This procedure is illustrative of a general method of preparing pyrimidines, wherein one condenses thiourea, guanidine, or an amidine with alkoxymethylenemalonic esters, alkoxy-methylenecyanoacetic esters, or alkoxymethylenemalononitrile. Kenner and Todd recently reviewed the synthesis of pyrimidines.6... 

The production of industrially important perfluoroalkane sulfonic acids is generally accomplished by electrochemical fluorination. This method of preparation remains expensive and proceeds in good yields only for short hydrocarbon chains.30 Recently however, Wakselman and Tordeux have described a chemical method for the preparation of trifluoromethane sulfonic acid.31 The procedure involves reaction of a metal selected from zinc, cadmium, manganese, and aluminum with sulfur dioxide in DMF, followed by the introduction of trifluoromethyl bromide under slight pressure. The intermediate sulfinate is subsequently oxidized by hydrogen peroxide, and then hydrolyzed which leads to formation of the trifluoromethane sulfonic acid. Successful extension of the sulfination process to the modification of PCTFE should result in the formation of a sulfinated polymer which can ultimately be oxidized to give a sulfonic-acid modified polymer. 

The method of Kim et al.[89-93] starts from the synthesis of the three-carbon phosphonium salt according to the modified method of Corey et alJ94,95] The Wittig reaction of the phosphonium salt with a Z-protected a-amino aldehyde using potassium hexamethyldisilazanide provides the ds-alkene without racemization. Efficient hydrolysis of the orthoester without double bond migration is achieved by acidolytic hydrolysis with aqueous hydrochloric acid in tert-butyl alcohol under reflux conditions. Then, an a-amino acid methyl ester is coupled. The desired epoxide product is obtained by treatment with 3-chloroperoxybenzoic acid. The epoxidation reaction is stereoselective and predominantly provides one isomer (R,S S,R = 4-10 1). The trans-epoxide can also be prepared using a trans-alkene-containing peptide. A representative synthetic procedure to obtain the ds-epoxide isostere is detailed below. 

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