Hexamethylphosphoramide, solution

In dimethyl sulfoxide (80% )-tert-butyl alcohol solution at 27° 3°C. h At complete reaction, moles oxygen absorbed per mole substrate. c In hexamethylphosphoramide solution. d tert-Butyl alcohol solution. 

The reduction of UCI4 to prepare these compounds can also be effected by sodium in hexamethylphosphoramide solution (43). 

The most effective solvent-catalyst systems for alkene isomerizations are hexamethylphosphoramide solutions of alkali alkylamides. For example, sodium dimethylamide in hexamethylphosphoramide is about 300,000 times as effective in catalyzing the isomerization of 2,4,4-trimethyl-1-pentene as is potassium / r/.-butoxide in dimethylsulfoxide. ... 

Figure 18-1 Visible spectra of quinacridone — absorption spectrum of quinacridone in hexamethylphosphoramide solution ...

Technora. In 1985, Teijin Ltd. introduced Technora fiber, previously known as HM-50, into the high performance fiber market. Technora is based on the 1 1 copolyterephthalamide of 3,4 -diaminodiphenyl ether and/ -phenylenediamine (8). Technora is a whoUy aromatic copolyamide of PPT, modified with a crankshaft-shaped comonomer, which results in the formation of isotropic solutions that then become anisotropic during the shear alignment during spinning. The polymer is synthesized by the low temperature polymerization of/ -phenylenediamine, 3,4 -diaminophenyl ether, and terephthaloyl chloride in an amide solvent containing a small amount of an alkaU salt. Calcium chloride or lithium chloride is used as the alkaU salt. The solvents used are hexamethylphosphoramide (HMPA), A/-methyl-2-pyrrohdinone (NMP), and dimethyl acetamide (DMAc). The stmcture of Technora is as follows ... 

The polyamides are soluble in high strength sulfuric acid or in mixtures of hexamethylphosphoramide, /V, /V- dim ethyl acetam i de and LiCl. In the latter, compHcated relationships exist between solvent composition and the temperature at which the Hquid crystal phase forms. The polyamide solutions show an abmpt decrease in viscosity which is characteristic of mesophase formation when a critical volume fraction of polymer ( ) is exceeded. The viscosity may decrease, however, in the Hquid crystal phase if the molecular ordering allows the rod-shaped entities to gHde past one another more easily despite the higher concentration. The Hquid crystal phase is optically anisotropic and the texture is nematic. The nematic texture can be transformed to a chiral nematic texture by adding chiral species as a dopant or incorporating a chiral unit in the main chain as a copolymer (30). 

Examples of alkali metal stannides are mainly limited to tris(trimethylsilyl)- and triphenylstannides. NMR studies of trimethyl- and tributylstannide in ether, THF, and hexamethylphosphoramide (HMPA, OP(NMe2)3) reveal the compounds to be monomeric in solution, as indicated by the large Li-Sn coupling. The addition of HMPA produces an... 

To test the validity of this mechanism, chromium carbonyl (1.0 g) was photolyzed under Ar at ambient temperature in a solution of methanol and hexamethylphosphoramide in the apparatus shown in Figure 5. The lamp was turned off periodically to check for the disappearance of slightly soluble Cr(C0) . Several photolyzing cycles were necessary to effect nearly complete conversion to the solvent-stabilized coordinately unsaturated species (equivalent to in Figure 4),... 

Paquette and coworkers reported the electrochemical behaviour of silyl-substituted cyclooctatetraene [72]. Two waves are observed with polarography in hexamethylphosphoramide (HMPA) solutions. The silyl substitution causes a... 

If pure oxazoline is required, residual amounts of hexamethylphosphoramide can be removed by elution of the ethereal solution through silica gel (20-40 mesh). 

A dry, 1-1., three-necked, round-bottomed flask is equipped with an overhead mechanical stirrer, a 125-ml. pressure equalizing dropping funnel fitted with a rubber septum, and a nitrogen inlet tube. The system is flushed with nitrogen, and 15.4 g. (0.1 mole) of geraniol (Note 1), 35 ml. of dry hexamethylphosphoramide (Note 2), 100 ml. of anhydrous ether (Note 3), and 50 mg. of triphenylmethane (Note 4) are placed in the flask. The stirred solution is cooled to 0° with an ice bath, and 63 ml. (0.1 mole) of 1.6Jf methyllithium in ether (Note 5) is injected into the addition funnel. The methyllithium solution is added dropwise over a period of 30 minutes. After the addition is complete, the funnel is rinsed by injecting 5 ml. of dry ether. 

Kemp et al., 1978). The rate is slowest in an aqueous solution and is enhanced in aprotic and/or dipolar solvents. The rate augmentation of 106—108 is attainable in dipolar aprotic solvents such as dimethyl sulfoxide and hexamethylphosphoramide (HMPA). Interestingly, the decarboxylation rate of 4-hydroxybenzisoxazole-3-carboxylate [53], a substance which contains its own protic environment, is very slow and hardly subject to a solvent effect (1.3 x 10-6 s-1 in water and 8.9 x 10-6 s-1 in dimethylformamide Kemp et al., 1975). The result is consistent with the fact that hydrogen-bonding with solvent molecules suppresses the decarboxylation. 

Figure 25 Cyclic voltammograms recorded in solutions of PVF in (a) CH2Cl2 (b) thf (c) hmpa (hexamethylphosphoramide)...

DMF, and Nbl jSDMF have been shown to involve O-bonded DMF molecules by i.r. studies. The latter compound may be constituted as [Nb-(DMF)g]l4 since no bands attributable to Nb—I were observed, and this formulation is supported by preliminary conductance data in DMF solution. E.s.r. studies of NbCl4,2L complexes (L = DMF, DMA, THA, dioxan, dimethoxyethane, hexamethylphosphoramide, or AA -diethylformamide) indicate that they adopt a trans-octahedral geometry. 

Ni[R-dtp]2 complexes form paramagnetic five-co-ordinate adducts with hexamethylphosphoramide Xo date no phosphate esters have been found to form adducts. However, the NMR spectra of solutions of Ni(R-dtp>2 complexes after long standing or gentle heating clearly show that scrambling reactions of the type ... 

Diffusion coefficients of Pb(II) determined in organic solvents - dimethylsulf-oxide and hexamethylphosphoramide -are about 1 order of magnitude lower than in aqueous solutions [33, 34, 37]. 

Solutions of dipositive lanthanide cations have been obtained in liquid ammonia, ethanol, THF, acetonitrile and hexamethylphosphoramide. Ions stabilized, or for which there is evidence for stabilization, include Nd2+, Dy2+ and Tm2+ as well as Eu2+, Yb2+ and Sm2+. The non-hydroxylic solvents are best at stabilizing M2+ ions. Thus NdCl2(THF)2 has been reported from the reduction of NdCl3 in THF by Na(naphthalene),657 and corresponding reductions of MC13 (M = Eu, Yb or Sm) have also been achieved.658 Solutions of solvated MI2 (M = Sm or Yb) in THF may easily be made by the quantitative reaction of the metal with 1,2-diiodoethane, producing ethane. The solid THF adducts may be isolated.659... 

In hexamethylphosphoramide, sodium reduction of lanthanide trihalides gives solutions of Eu2+ (pale yellow), Yb2+ (yellow), Sm2+ (red-violet) and Tm2+ (red-brown). The latter has a half-life at 4.5 hours. The solution of SmCI2 tends to be more stable (half-life, 60 hours) than those of SmBr2 (30 hours) or Sml2 (25 hours).660,661 In liquid ammonia, Eu2+ or Yb2+ may be... 

B. Reduction of 1-Dodecyl Tosylate to n-Dodecane. In a dry 200-ml. three-necked flask equipped exactly as described in Section A are placed 50 ml. of hexamethylphosphoramide (HMPA), 1-dodecyl tosylate (6.80 g., 0.0201 mole) (Note 8), and sodium cyanoborohydride (5.02 g., 0.080 mole) (Note 3). The solution is stirred at 80° for 12 hours (Note 9), then diluted with 50 ml. of water, and extracted with three 60-ml. portions of hexane. The hexane solution is washed twice with water, dried over anhydrous magnesium sulfate, and then concentrated at reduced pressure with a rotary evaporator. Distillation of the residue through a short-path apparatus (Note 5) (Cautionl foaming) affords 2.49-2.64 g. (73-78%) of w-dodecane, b.p. 79-81° (3.75 mm.) na4D 1.4217 (lit.,3 n20d 1.4219) (Note 7). 

A solution of 2.57 g of l-(2, 4 -dichlorophenyl)-2-(N-imidazolyl)ethanol in 10 ml of hexamethylphosphoramide was dropped at 25°C into a suspension of 0.52 g of sodium hydride (50% in oil) in 5 ml of hexamethylphosphoramide. When hydrogen emission was over, the salification was completed by heating for 1 hour at 50°C. After cooling to 25°C, 2.58 g of l-chloromethyl-4-phenylthiobenzene were added. The temperature was raised to 50°C and maintained at that temperature for 12 hours. At the end of the reaction, the mixture was poured into 200 ml of water, the product was extracted with diethyl ether, the solvent was evaporated off and the residue was purified twice on a silica gel column, using ethyl acetate as eluant and testing the various fractions by TLC. The solvent was evaporated off the middle fractions... 

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