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Pyridine-water

A mixture of water/pyridine appears to be the solvent of choice to aid carbenium ion formation [246]. In the Hofer-Moest reaction the formation of alcohols is optimized by adding alkali bicarbonates, sulfates [39] or perchlorates. In methanol solution the presence of a small amount of sodium perchlorate shifts the decarboxylation totally to the carbenium ion pathway [31]. The structure of the carboxylate can also support non-Kolbe electrolysis. By comparing the products of the electrolysis of different carboxylates with the ionization potentials of the corresponding radicals one can draw the conclusion that alkyl radicals with gas phase ionization potentials smaller than 8 e V should be oxidized to carbenium ions [8 c] in the course of Kolbe electrolysis. This gives some indication in which cases preferential carbenium ion formation or radical dimerization is to be expected. Thus a-alkyl, cycloalkyl [, ... [Pg.116]

Brisset. J.-L. Solnbilities of varions nitroanilines in water-pyridine, water-acetonitrile, and water-ethylene glycol solvents. J. Chem. Eng. Data, 30(4) 381-383. 1985. [Pg.1636]

Nickel(II) complexes of 8-hydroxyquinoline, HL, are well known from the viewpoint of analytical chemistry. The brown, diamagnetic complex ML2 has cis square planar coordination (342). The same coordination occurs in C6H6 and CHC13 solutions. In water, pyridine or dioxane, this complex is green and paramagnetic, as is the solid hydrate NiL2-2H20. [Pg.214]

For the optimum HPLC separation, the liquid chromatograph was connected to a mass detector. A column (250 X 5-mm ID) of SPHERISORB C8 (5-yttm particles) was eluted with a solvent gradient, with reservoir A containing methanol and reservoir B containing water-pyridine-acetic acid (98.5 1.5 0.025). The mobile phase was A B = 92 8, and this composition was held for 10 min. The flow rate was 0.75 ml/min. [Pg.185]

N,N-dImethylformamide, see N,N-dimethylformamide-methanol-water -pyridine, see methanol-pyridine-water -2-propanol, see 2-propanol-water Pyridine, see pyridine-water... [Pg.691]

This order of base activity corresponds almost exactly to that observed in the formation of pyrroles from ketoximes and acetylene, evidently for the same causes. The failure of trimethylbenzylammonium hydroxide to catalyze the reaction of vinylation is believed (59MI1 66MI1) to be caused by its lack of coordination. Along with inhibition of the reaction with water, pyridine, o-phenanthroline, and diketones, this indicates the reaction occurs by complex ionic mechanisms in which the participation of the complex ion as an intermediate is possible. [Pg.190]

Another unexpected rearrangement was encountered in the synthesis of 1 - e/u -valiolamine, when the alkene 4 was subjected to dihydroxylation conditions. Thus, heating of a mixture of 4 with a catalytic amount of OSO4 in a water/pyridine/t-butanol mixture containing trimethylamine N-oxide under reflux for 2 days gave a mixture of 5 (29%) and the a-diol 6 (14%) together with 46% of unchanged alkene 4. [Pg.142]

Gold - Water-soluble gold porphyrin ions, [Au(TPPS4)]3 and [Au(TMPyP)]5+ (as the 3- and 4-pyridyl isomers), were obtained from the respective free-base porphyrins in a mixture of water/pyridine/lithium chloride containing KAuCl4 [142]. The products were purified by extraction with acetone and methanol and subsequent HPLC, however, the counterions were not determined. [Pg.20]

Solvent CC14 + C2H5OH water + pyridine + alcohols cyclohexene polystryene matrices X, > 350 nm ... [Pg.209]

The substitution path b) (Eq. (94) ), is favored by the following experimental conditions low current density, grapliite as anode material, alkaline medium, water or water-pyridine as solvent, and admixture of foreign ions e.g., bicarbonate, sulfate, perchlorate, dihydrogen phosphate, Pb2+, Mn2+, Cu2+, Fe2+, Co2+. The carbonium ion path b) can furthermore be expected for carboxylates RR CHOO with a-substituents R such as alkyl, phenyl 198 hydroxy, halogen 1 amino, or alkoxy. These substituents facilitate oxidation of the intermediate alkyl radical R to the carbonium ion R+. Product formation occurs via carbonium ions and not, as is also conceivable, via mixed coupling of R with Nu ... [Pg.63]

Anodic bisdecarboxylation is normally conducted at a platinum anode in water-pyridine-triethylamine as electrolyte and with both carboxyl groups neutralized. Synthetic applications of this method are illustrated by the following examples (Eq. (139-145)). [Pg.93]

Another variation on the same theme is the predominant formation of alcohols in the oxidation of carboxylates in mixtures of pyridine and water. To take but one example, the oxidation of a 3-bicyclo[3,l,0] hexanecarboxylate in water-pyridine (3 1) gave isolated yields of alcohols of up to 60% (Gassman and Zalar, 1966), although we generally think of pyridine as a far stronger nucleophile than water by a factor of perhaps 103- 104. And, in these two examples, why does the carboxylate itself not function as a nucleophile (as can be found in other cases under different conditions) ... [Pg.92]

The solvents should be free of air and water. Pyridine and 1,5-cyclooctadiene were distilled under nitrogen. Tetrahydrofuran was distilled from lithium tetrahydridoaluminate(l —) and stored over sodium in a nitrogen atmosphere. Pentane was dried over molecular sieve and sparged with nitrogen. [Pg.113]

Good lignin solvents (e.g., acetone/water, dioxane/water, pyridine, ethylene chloride/ethanol, and acetic acid) exhibit strong IR bands and therefore are not commonly used for solution state IR investigations. An exception is chloroform. [Pg.235]

PROP White to brownish-gray powder. Disagreeable odor. Sol in water, pyridine, ethanol less sol in acetone, ether, chloroform, pentane, benzene. [Pg.121]

It is noted that the magnitude of the contact contribution varies considerably between the and resonances. In order to obtain structural information on the lanthanide complexes at least six Gj values are, in general, required (three polar coordinates to fix the position of the lanthanide ion relative to the molecule, two additional angles to define the main magnetic axis orientation, and one signed value for the proportionality constant). The six nuclei used to provide these Gj values need not necessarily be protons. In a later paper Reilley et al. (388) discuss certain refinements of their method and apply it to a wide variety of LSR complexes including those of water, pyridines, alcohols, anilines, aliphatic amines, and ketones. The contact contributions of the C shifts of Ln(DPA)3 and Ln(MDPA)3 complexes are found to be important even for carbons five bonds removed from the lanthanide ion. (390)... [Pg.70]

By an analogous method the dithionate salt has been obtained from ds-[tetra-ammineaquahydroxochromium(Ill)] chloride.In the method described here, the aquachloro complex is hydrolyzed at room temperature in a water-pyridine mixture and the resulting cis-[tetraammineaquahydroxochromium(III)] complex is isolated as the dithionate salt. The crude product is contaminated with a small amount of sulfate but has a purity suitable for the syntheses of di-p-hydroxo-bis[tetraamminechromium(III)] salts given in Section H. ds-[Tetra-ammineaquachlorochromium(III)] sulfate is described in Section A. [Pg.80]


See other pages where Pyridine-water is mentioned: [Pg.149]    [Pg.251]    [Pg.279]    [Pg.119]    [Pg.120]    [Pg.111]    [Pg.119]    [Pg.120]    [Pg.247]    [Pg.54]    [Pg.97]    [Pg.19]    [Pg.291]    [Pg.125]    [Pg.32]    [Pg.33]    [Pg.221]    [Pg.373]    [Pg.387]    [Pg.27]    [Pg.168]    [Pg.327]    [Pg.3493]    [Pg.701]    [Pg.343]    [Pg.131]    [Pg.125]    [Pg.32]    [Pg.33]    [Pg.204]    [Pg.96]    [Pg.82]    [Pg.90]   
See also in sourсe #XX -- [ Pg.2377 ]




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