Solvents reaction with powders

A CF3Cu solution can also be prepared by the reaction of bis (trifluoromethyl) mercury [90] or AT-trifluoromethyl-AT-nitrosotrifluoromethanesulfonamide (TNS-Tf) [91] with activated copper powder in dipolar aprotic solvents. Reaction with aryl iodides gave the corresponding trifluoromethylated aromatics in good yields. (Scheme 29). 

For solvent extraction of a tetravalent vanadium oxyvanadium cation, the leach solution is acidified to ca pH 1.6—2.0 by addition of sulfuric acid, and the redox potential is adjusted to —250 mV by heating and reaction with iron powder. Vanadium is extracted from the blue solution in ca six countercurrent mixer—settler stages by a kerosene solution of 5—6 wt % di-2-ethyIhexyl phosphoric acid (EHPA) and 3 wt % tributyl phosphate (TBP). The organic solvent is stripped by a 15 wt % sulfuric acid solution. The rich strip Hquor containing ca 50—65 g V20 /L is oxidized batchwise initially at pH 0.3 by addition of sodium chlorate then it is heated to 70°C and agitated during the addition of NH to raise the pH to 0.6. Vanadium pentoxide of 98—99% grade precipitates, is removed by filtration, and then is fused and flaked. 

Alkaloids of Pot Curare. This variety of curare is a dark brown, comparatively dry extract. According to Boehm, it contains protocurine, colourless hair-like needles, m.p. 306° (dec.), a base of low toxicity and yielding crystalline salts. A second alkaloid of similar type is protocuridine prisms, m.p. 274-6°, sparingly soluble in all ordinary solvents. The poisonous constituent is protocurarine, a red powder, easily soluble in water, and giving characteristic colour reactions with nitric acid and with oxidising agents in sulphuric acid, this latter reaction indicating a Strychnos spp. as a possible botanical source. 

Under N2, clean Li metal (0.17 g, 25 mmol) was placed in a round-bottom flask with a solvent mixture of MeOH (3 mL) and pcntan-t-ol (17 mL). The mixture was heated under N, until the reaction with Li was complete. Then, naphthalene-2,3-dicarbonitrilc (2 g, 11 mmol) was added to the mixture which turned green-brown the mixture was refluxed for 3h. The brown powder, obtained after cooling and removal of the solvent under reduced pressure, was dissolved in anhyd acetone (20 mL) and then hexane (70 mL) was added. The green precipitate was separated from the brown solution by filtration. This purification by precipitation was repeated twice. The green precipitate was placed in a Soxhlet extractor and extracted for 3 h with acetone (200 mL) in order to separate the product from the insoluble metal-free species and LiOH. The acetone solution was evaporated down to a volume of 20 mL. The product precipitated after the addition of hexane (70 mL). This latter purification step was performed several times yield 1.29 g (64%). 

Allenyl iodides can be prepared from propargylic mesylates by Sn2 displacement with LiCuI2 (Eq. 9.143) [118]. The reaction proceeds primarily by an anti pathway with slight racemization. Metallation of these iodides with powdered indium in various donating solvents leads to transient allenylindium intermediates which react in situ with aldehydes to afford anti homopropargylic alcohols (Table 9.52). Additions... 

The commonest solvent for TPAP in organic oxidations is CH Clj (DCM), normally in conjunction with 4 A powdered molecular sieves (PMS) to remove water formed during the oxidation. Addition of CH3CN, as in many Ru-catalysed oxidations, makes reactions with TPAP/NMO more effective [59], and occasionally CH3CN is used as the only solvent [159]. Ionic liquids, e.g. [emim](PF )/PMS [479] and [bmim](BF )/PMS [480] have been used with TPAP/NMO. It has also been used in supercritical CO [457]. 

In the past most enzymologists tacitly assumed that the external medium in which enzymes act must be aqueous. However, many enzymes function well in media containing largely hydrocarbons. Enzymes in a dry, powdered form have been suspended directly in organic solvents.192 193 Under these conditions, enzymes may contain only tightly bound "structural" water, together with less than one equivalent of a mono-layer of water outside the protein. The enzymes often remain active and are able to catalyze reactions with an altered substrate specificity as well as different reactions overall. 

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