Vanadous bromide

Vanadous Bromide, vanadium tribromide, VBr3, is conveniently obtained synthetically. When powdered vanadium is gently warmed with pure, dry bromine, combination takes place readily, considerable heat is evolved and the tribromide is formed. Ferrovanadium alloy gives the same product.7 It is also obtained by the action of pure,... 

I-A1ON0-2-NAPHIH0L-4-SULE0NIC acid, 11, 72 16, 91 17, 91 Aminonaphtholsulfonic acids, coupling to form azo dyes, 16,16 p-Aminophenol, 16, 39 Aminopiperole, 16, 6 /3-Ahinopropionic acid, 16, 1 4-Aminoveratrole, 16, 4 Ammonium dichromate, 16, 74 Ammonium formate, 17, 77 Ammonium thiocyanate, 16, 74 Ammonium vanadate, 13, 1 to w-Amyl alcohol, IS, 17 hri.-Amyl alcohol, 13, 68 -Amylbenzene, 10, 4 -Amyl borate, 13, 17 -Amyl bromide, 16, 41 iso-Amyl iodide, 13, 62 n-Amyl iodide, 13, 62 n-Amybnagnesium bromide, 16, 41... 

Lithium aluminum hydride reduced )J-azidoethylbenzene to j8-aminoethyl-benzene in 89% yield [600], The azido group was also reduced with aluminum amalgam (yields 71-86%) [149], with titanium trichloride (yields 54-83%) [601], with vanadous chloride (yields 70-95%) [217] Procedure 40, p. 215), with hydrogen sulfide (yield 90%) [247], with sodium hydrosulfite (yield 90%) [259], with hydrogen bromide in acetic acid (yields 84-97%) [232], and with 1,3-propanedithiol (yields 84-100%) [602]. Unsaturated azides were reduced to unsaturated amines with aluminum amalgam [149] and with 1,3-propane-dithiol [602]. 

Among water soluble retardants (nondurable type) may be cited Amm bromide, Amm tungstate, Na vanadate, Li hydroxide, Na molybdate, K or Na hydroxide, Amm metavanadate, DiAmm phosphate Zn chloride. 

Alkyl hydroperoxides, including ethyl hydroperoxide, cuminyl hydroperoxide, and tert-butyl hydroperoxide, are not used by V-BrPO to catalyze bromination reactions [29], These alkyl hydroperoxides have the thermodynamic driving force to oxidize bromide however, they are kinetically slow. Several examples of vanadium(V) alkyl peroxide complexes have been well characterized [63], including [V(v)0(OOR)(oxo-2-oxidophenyl) salicylidenaminato] (R = i-Bu, CMe2Ph), which has been used in the selective oxidation of olefins to epoxides. The synthesis of these compounds seems to require elevated temperatures, and their oxidation under catalytic conditions has not been reported. We have found that alkyl hydroperoxides do not coordinate to vanadate in aqueous solution at neutral pH, conditions under which dihydrogen peroxide readily coordinates to vanadate and vanadium( V) complexes (de la Rosa and Butler, unpublished observations). Thus, the lack of bromoperoxidase reactivity with the alkyl hydroperoxides may arise from slow binding of the alkyl hydroperoxides to V-BrPO. 

Analogous to the preceding cw-dioxovanadium(V)-catalyzed system of bromide oxidation by dihydrogen peroxide, Secco carried out a detailed kinetic analysis of vanadate-catalyzed oxidation of iodide by dihydrogen peroxide [75], Peroxovanadate species (i.e., V0[02]+ and V0[02]2 ) or their hydronated forms oxidize iodide in acidic aqueous solution, forming V02+ and V0(02)+, respectively however, once V0(02)+ and V0(02)2 are consumed, iodide reduces... 

FIGURE 2.3 51V NMR spectrum of vanadate in a nematic lyotropic liquid crystalline solution. The spectrum shows quadrupole-split signals from V and V4, while the signal of V2 is broadened. The quadrupole splittings are 200 Hz and 5.35 kHz for V and V4, respectively. The spectrum was obtained from a tetradecyltrimethylammonium bromide (TDTMABr) mesophase of composition TDTMABr, 160 mg decanol, 30 mg D20,450 mg NaCl, 10 mg. 

Interestingly, there is a close structural correspondence between the active sites of the haloperoxidases and the acid phosphatases that allows both peroxidase and phosphatase activity from the two types of enzymes [49-51], For instance, recombinant acid phosphatases from both Shigella flexneri and Salmonella enterica ser. typhimurium, when substituted by vanadate, are able to oxidize bromide when in the presence of hydrogen peroxide. However, the turnover rate is quite slow, which is in accord with the phosphatase active sites not being optimized for peroxidase activity [52],... 

Chromates, vanadates, and cerium salts give colour reactions with the reagent and should therefore be absent. Iron salts give a yellow colour with hydrogen peroxide, but this is eliminated by the addition of syrupy phosphoric acid. Fluorides bleach the colour (stable [TiF6]2 ions are formed), and large amounts of nitrates, chlorides, bromides, and acetates as well as coloured ions... 

Similarly, when vanadate is introduced in the active site of the acid phosphatases, these artificial enzymes are able to oxidize bromide in the presence of H2O2 and to sulfoxidize sulfides in an enantioselective manner. The turnover frequency... 

Reaction of the tetraethylammonium salt of the tetracarbonyl[l,2-bis(diphenylphosphanyI)-ethane]vanadate complex 37 with 1,2,3-triphenylcyclopropenylium bromide (33) afforded the hydrogenated acyl complex of the type 38 with the acyl group linked to the metal via its carbon and oxygen atoms formally acting as a three-electron donor. The structure was determined by X-ray crystallography. ... 

To a solution of tetraethylammonium tctracarbonyl[l,2-bis(diphenylphosphanyl)ethane]vanadate (2.40g, 3.47 mmol) in THF (250 mL) was added an excess molar amount of l,2,3-triphenylcyclopropenylium bromide at 20 "C under irradiation with a 125-W high-pressure Hg lamp vigorous gas generation occurred. After 30 min, the brown mixture was filtered, evaporated, and washed repeatedly with 50-mL portions of EtjO. The product was obtained after washing with MeOH and recrystallization (CH Clj/hexane 1 1) yield 0.470 g (16.4%) mp 98-104" C (dec.). 

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