Cadmium bromide, reaction

It is apparent from the foregoing that a more specific method for the determination of xylan would be desirable. To this end, the determination of xylose, after acid hydrolysis of the polysaccharide material, has been attempted. Xylose may be oxidized to xylonic acid which can be precipitated with cadmium bromide as the double salt, but the precipitation is not quantitative. Xylose forms an insoluble, crystalline di-O-benzylidene dimethyl acetal which permits identification in the presence of other sugars, but the necessity for anhydrous reaction conditions precludes the adaptation of this method to ordinary analysis. AVise and Ratliff prepared this derivative of both d- and L-xylose, as well as analogous derivatives from other aromatic aldehydes, and concluded that, with either the di-O-benzylidene or the di-O-(p-isopropylbenzylidene) dimethyl acetal, an excellent, highly specific, qualitative test was available for d- or n-xylose. 

Hudson and Isbell developed the buffering action further. Calcium or barium benzoate was employed to maintain the oxidation solution at a pH of 5-6, and the reaction mixture was kept in the dark. Lactose was converted to lactobionic acid without hydrolysis, and 96 and 90% yields of calcium D-gluconate and cadmium D-xylonate-cadmium bromide were reported by the use of this method. Isbell and Pigman developed this method later into a valuable tool for the study of the mechanism of bromine oxidation and for the study of the structure of various aldoses (see pages 171, 182). 

Cadmium carbonate may be especially useful In this regard (1 ) the cadmium bromide formed In this reaction likely acts as a catalyst. Silver perchlorate (0.2 mol/mol aglycone) has been reported to be an effective catalyst when used together with silver carbonate (13). Phase transfer catalysis (PTC) conditions were used for synthesis of methyl (2-benzyloxy-4-forBiylphenyl... 

The method of converting vinyl to carbonyl groups by ozonolysis has received much attention and has been successfully applied to a variety of phosphonates containing homoallyl groups, including oc-functionalized phosphonates. The homoallyl group is introduced by the reaction of allyl-bromide with diethyl 1-lithioalkylphosphonates. - A convenient preparation of diethyl 1,1-difluoro-2-formylethylphosphonate (Scheme 5.28) involves the ozonolysis of diethyl l-allyl-1,1-difluoromethylphosphonate, which, in turn, is prepared from diethyl bromodifluoromethylphosphonate in 62% yield by treatment of its cadmium bromide derivative with allyl bromide. ... 

The initial tests of the sodium dispersion-metal halide system were made with ferric chloride, fortunately, and with a nonaqueous solvent in which ferric chloride was soluble. Thus, ferric chloride was present as a solution and, consequently, presented maximum surface for contact with the sodium particles. This feature, coupled with the lower activation energy requirements, permitted the reaction to proceed at temperatures well below room temperature and established the operability of the method. The success of the initial (ferric chloride) tests lent encouragement to tests on other metal systems and prompted continued investigations when the initial runs at lower temperatures failed. The discovery of the threshold, or trigger, temperature for nickel (II) chloride reduction paved the way for successful reduction of other metal halides such as manganese (II) chloride, cobalt (II) chloride, and cadmium bromide. 

Only a few reports of unsacurated fluormated cadmium compounds have appeared The direct reaction of perfluoroalkenyl lod ides or bromides with cadmium powder in DMF stereospecifically gives the vinylcadmium compounds [143] (equation 110) Table 5 shows several typical vinylcadmiums prepared by this method. 

The perfluoroallylcadmium reagent can be prepared similarly by direct reaction of perfluoroallyl iodide with cadmium metal [146] (equation 113). Reaction of this cadmium reagent with ally bromide gives F2C=CFCp2CH2CH=CH2 in 78% yield [146]. 

The addition reaction requires the presence of 4 equivalents of HMPA, thus partial racemization of optically active aldehydes under these basic conditions is anticipated. Unfortunately, the addition of magnesium bromide, zinc chloride or cadmium iodide reverses the regioselectivity11 ... 

These are well known nonelectrodic reactions38. The electrochemical processes are meant to take care of the large amount of elemental lead set free in transmetallation, and has been devised to confine all the reactions to a single-compartment cell process. The cell in the present example is undivided, with Cd and Pb electrodes in DMF or DMSO solutions containing TBAP and Etl(10%) with Nal(5%). A sacrificial cadmium cathode is oxidized to diethylcadmium by ethyl iodide or, less readily, with ethyl bromide. 

Di-n-butylcadmium was prepared by the rapid addition of cadmium chloride (50.4 g, 0.275 mol) to a cooled solution of n-butylmagnesium bromide formed from magnesium (12.15 g, 0.50 mol) and n-butyl bromide (75.4 g, 0.55 mol) in anhydrous diethyl ether (550 ml). Following the addition, the reaction mixture was stirred at 0°C for 2 h. The di-n-butylcadmium reaction mixture, including the precipitate, was then added to a stirred solution of phosphorus trichloride (85.9 g,... 

The enhancement of SWV net peak current caused by the reactant adsorption on the working electrode surface was utilized for detection of chloride, bromide and iodide induced adsorption of bismuth(III), cadmium(II) and lead(II) ions on mercury electrodes [236-243]. An example is shown in Fig. 3.13. The SWV net peak currents of lead(II) ions in bromide media are enhanced in the range of bromide concentrations in which the nentral complex PbBr2 is formed in the solntion [239]. If the simple electrode reaction is electrochemically reversible, the net peak cnnent is independent of the composition of supporting electrolyte. So, its enhancement is an indication that one of the complex species is adsorbed at the electrode snrface. 

Cadmium(II) bromide Cd + 2Br " —> CdBr. This compound is used in photography, engraving, and lithography. The other halogen elements also combine with cadmium in a similar ionic reaction as with bromine. 

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. 

Barbier reaction Samarium(II) iodide, 270 Benzoannelation Chromium carbene complexes, 82 Dicarbonylcyclopentadienylcobalt, 96 Ethyl (Z)-3-bromoacryIate, 130 Grignard reagents, 138 Methyl acrylate, 183 Methyllithium, 188 Ruthenium(III) chloride, 268 Benzoin condensation Benzyltriethylammonium chloride, 239 3-EthyIbenzothiazolium bromide, 130 Benzoylation (see also Acylation) Cadmium, 60 Dibutyltin oxide, 95 Birch reduction Birch reduction, 32... 

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