Methanol-water salts

The hydrochloride salt is dissolved in 100 ml of methanol and 110 ml of 15% ammonium hydroxide is added in several portions. The mixture is cooled and the crystalline product is filtered and washed with methanol-water (1 1). The dried 3f5-hydroxy-16o -methoxylaminopregn-5-en-20-one acetate (114) obtained in ca. 90% yield is recrystallized from acetone mp 147-149°. 

The filtrate is diluted with 140 ml of 50% methanol-water and placed in the refrigerator for 3 days. The thick sheet of crystalline material which forms on the surface is removed by filtration and washed with 75 % acetic acid to yield 32.5 g of crude product. The filtrate is again cooled overnight and an additional 8.7 g of solid is removed. The crops are combined and the material, mp 120-124°, which is highly colored due to chromium salts, is recrystallized twice from methanol to yield 27 g (24 %) of the keto acid (69) mp 127-129° 78° (CHCI3). 

Asymmetric hydrogenolysis of epoxides has received relatively little attention despite the utility such processes might hold for the preparation of chiral secondary alcohol products. Chan et al. showed that epoxysuccinate disodium salt was reduced by use of a rhodium norbornadiene catalyst in methanol/water at room temperature to give the corresponding secondary alcohol in 62% ee (Scheme 7.31) [58]. Reduction with D2 afforded a labeled product consistent with direct epoxide C-O bond cleavage and no isomerization to the ketone or enol before reduction. 

The sequence Gly-Glu-Arg... folds better in water than in methanol as shown below. Many folding investigations have shown clearly different influences of the solvents. Even in many cases, folding can be enhanced in methanol, or methanol/water mixtures, trifluoroethanol, buffer solutions, or higher concentrated salt solutions. 

Solution 11a Dissolve 2.25 g sodium nitrite in 10 ml water and make up to 50 ml with methanol. Diazonium salt —Atom amine Azo dye ... 

This problem was resolved by Nakae et al. [7] using non-polar octadecylsilica as the stationary phase and a solution of 0.1 M of sodium perchlorate in methanol/water (80 20) as the mobile phase. The ternary system (water-alcohol-salt), previously used by Fudano and Konishi [8] as an eluent for the separation of ionic surfactants at higher concentrations, induced the so-called salting out effect . The addition of the organic solvent to the water modified the polarity of the eluent and produced a good separation within a short period of time [9]. It also has the function of dissociating the surfactant micelles in individual molecules that are dissolved in the eluent [8], The presence of the salt (NaC104) in the mobile phase has a considerable influence on... 

The sequence of the selectivities towards cations is also solvent dependent for dibenzo-18-crown-6 [11] the sequence is K+ > Na+ > Rb+ > Cs+ in water, methanol, dimethylformamide and dimethyl sulfoxide (Dechter and Zink, 1976 Srivanavit et al., 1977), whereas it is Na+ > K+ > Rb+ > Cs+ in acetonitrile (Hofmanova et al., 1978). A reversal of the K+/Na+ selectivity on going to apolar aprotic solvents was also observed for fluorenyl salts (Wong et al., 1970). Whereas for alkali cations the sequence of binding constants and enthalpies are the same in water (Izatt et al., 1976a), they differ considerably in methanol/water mixtures (Izatt et al., 1976b), dimethyl sulfoxide and acetone (Arnett and Moriarity, 1971). 

Another type of ternary electrolyte system consists of two solvents and one salt, such as methanol-water-NaBr. Vapor-liquid equilibrium of such mixed solvent electrolyte systems has never been studied with a thermodynamic model that takes into account the presence of salts explicitly. However, it should be recognized that the interaction parameters of solvent-salt binary systems are functions of the mixed solvent dielectric constant since the ion-molecular electrostatic interaction energies, gma and gmc, depend on the reciprocal of the dielectric constant of the solvent (Robinson and Stokes, (13)). Pure component parameters, such as gmm and gca, are not functions of dielectric constant. Results of data correlation on vapor-liquid equilibrium of methanol-water-NaBr and methanol-water-LiCl at 298.15°K are shown in Tables 9 and 10. 

The reaction mixtures were either heated in sealed tubes or ignited in a bomb with a hot filament. The by-product salts are then removed by washing with an appropriate solvent (generally methanol, water and diethyl ether). These reactions are highly exothermic and generally self-propagating. Accidental self-detonation of the mixture may be observed on mixing the reactants. 

The addition of an amino acid to mixed solvents at selected temperatures can be a means to compensate even partially for the decrease of dielectric constant due to the solvent addition. Limitations are imposed by the solubility of the amino acid in such mixtures for instance, there is a salting-out effect in methanol-water 50 50 at 25°C when the concentration of glycine is about 0.5 Af (8 20). 

Transfer chemical potentials for the low-spin amine-diimine complexes [Fe(tsba)2] " with tsba = (8 were estimated from the solubilities of their perchlorate salts, in methanol-water mixtures.Solubility and transfer chemical potential data are also available for [Fe(Me2bsb)3] " " in several nonaqueous solvents. One of the main purposes in determining transfer chemical potentials for these iron(II)-diimine complexes is to enable dissection of reactivity trends into initial state and transition state components for base hydrolysis (see next section) in binary aqueous solvent mixtures. Systems for which this has been achieved are indicated in Table 8. 

Fe(5N02phen)3] + aquation in ternary water-Bu OH-polyethyleneglycol (PEG400). " Kinetic patterns for systems of these types have been the subject of theoretical analyses, as in the application of the Savage-Wood Group Additivity principle to [Fe(5N02phen)3f" " aquation in a variety of water-rich binary aqueous mixtures and in aqueous salt solutions " and in the Kirkwood-Buff treatment of preferential solvation of initial and transition states for [Fe(phen)3] + aquation in methanol-water " and for [Fe(gmi)3] " " aquation in Bu OH + water. " ... 

EXAFS studies on tris-maltolatoiron(III) in the solid state and in solution, and on [Fe(Ll)3] hydrate, pave the way for detailed investigation of the hydration of complexes of this type in aqueous media.Solubilities and transfer chemical potentials have been determined for tris-maltolatoiron(III) in methanol-water, and for tris-etiwlmaltolatoiron(III) in alcohol-water mixtures and in isobutanol, 1-hexanol, and 1-octanol. Solubility maxima in mixed solvents, indicating synergic solvation, is relevant to trans-membrane transport of complexes of this type. Solubilities of tris-ethylmaltolatoiron(III) and of [Fe(Ll)3] have been determined in aqueous salt solutions (alkali halides NH4 and NR4 bromides). ... 

The imidazoUdinonium salt 12 HC1 was shown to be an excellent catalyst for the Diels-Alder reaction of a,P-unsaturated aldehydes 15 (Scheme 2) [3]. Using just 5 mol% of the catalyst at room temperature in a methanol/water mixture (19 1), adducts were obtained in excellent yield (75-99%) and enantiomeric excess (84-93%). The simplicity of these transformations, operating at room temperature in the presence of moisture and air without the need for rigorous purification of solvents and reagents, makes these procedures highly practical and opened up a new area for further research. 

The phosphine in the reaction mixture is partially in the form of the quaternary salt. In highly polar solvents, e.g. water and methanol, the salt formation can predominate leading to total loss of electron-donating phosphine and to catalyst deactivation. In protic solvents the iodide may form a stable iodotricarbonyl nickel complex. 

Rh/19 (n=1,2,3,6) catalysts were used in the hydroformylation of 1-octene in the presence of conventional tensides such as the sodium salt of the dodecyl-benzene sulfonic acid (0.5 wt.%) in an 1-octene/nonane/methanol/water (60/34/50/ 56) mixture.121 With Rh/19 (n=6) the TOF achieved was 28 h. 1,21... 

Figure 6. Plot of y vs. x (salt-free basis) methanol-water-potassium acetate 764 mmHg a 12 = —0.20, a 23 = 0.30, a 3 = 0.0 (ideal)...

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