Phase acid-facilitated

The catalytic effect of quaternary ammonium salts in the basic liquid liquid two-phase alkylation of amines [1-3] is somewhat unexpected in view of the low acidity of most amines (pKfl>30). Aqueous sodium hydroxide is not a sufficiently strong base to deprotonate non-activated amines in aqueous solution and the hydroxide ion is not readily transferred into the organic phase to facilitate the homogeneous alkylation (see Chapter 1). Additionally, it is known that ion-pairs of quaternary ammonium cations with deprotonated amines are decomposed extremely rapidly by traces of water [4]. However, under solidrliquid two-phase conditions, the addition of a quaternary ammonium salt has been found to increase the rate of alkylation of non-activated amines by a factor of ca. 3-4 [5]. Similarly, the alkylation of aromatic amines is accelerated by the addition of the quaternary ammonium salt the reaction is accelerated even in the absence of an inorganic base, although under such conditions the amine is deactivated by the formation of the hydrohalide salt, and the rate of the reaction gradually decreases. Hence, the addition of even a weak base, such as... 

This drug can be used as a carboxylic acid ester, in particular, as an acetate. It causes the mucous membranes of the uterus to move into the secretory phase, which facilitates development of impregnated oocytes. It reduces the excitability and contractility of uterine musculature. It is used for amenorrhea, uterine bleeding, infertility, miscarriage, myoma, mastopathy, endometrial cancer, and other pathologies. Synonyms of this drug are conce-plan, norfor, brevinor, and many others. 

A matrix solid-phase dispersion technique has been further applied for the determination of oxytetracycline, tetracycline, and chlortetracycline in milk (290, 311), using octadecylsilyl- (Cjg) derivatized silica as the solid phase. To facilitate extraction of the tetracycline antibiotics from milk, addition of an equal ratio of EDTA to oxalic acid has been found advantageous. 

Iodine and sulphur dioxide are combined with water in the Bunsen reaction to create two immiscible acid phases. The separation of these phases is facilitated by the presence of excess iodine. The lighter, sulphuric acid phase is decomposed first to S03, and then to S02. S02 formation typically occurs in the presence of a catalyst at temperatures above 800°C. The S02 and water are recycled back to the Bunsen reaction for reuse. 

The analyte content was 5-10 ppm, with a ligand concentration in excess (ca. ten times with respect to the metal ion). The pH was adjusted with a proper buffer (acetic acid / acetate or chloroacetic acid / chloroacetate) and inert salt (NaNO ) was added in order to increase the density of the aqueous rich lower phase, which facilitates fast centrifugation. 

The acid dependency observed in practice hal been only approximately inverse third power. Impurities in Cleanex feed solutions often cause a departure from ideality (e.g., by common-ion effect or by consumption of some of the HDEHP), and we have not been able to control the extraction of the actinide elements solely by monitoring the aqueous-phase acidity. Fortunately, when processing transplutonium elements, the high specific activity of 21+I+Cm facilitates the detection of that isotope in both phases, thus permitting a rapid determination of the degree of extraction. The extraction coefficients of the trivalent actinides and lanthanides are all quite similar, so the 21+1+Cm serves as an excellent marker for all the extracted ions. 

Essentially, ESI is said to rely on the production of ions while in solution, before being coaxed into the gas phase through nebulization, droplet evaporation, and coulombic explosions [29]. Therefore, it is a general rule that basic drugs should be analyzed using an acidic mobile phase to facilitate production of positively charged, protonated analytes. 

Table 5-1. Enantioselectivities determined for several drugs. All experiments were performed at room temperature, except those marked with, which were performed at 4 °C. In some cases a lipophilic anion was used to facilitate the solubilization of the drug in the organic phases (PFj = hexafluorophosphate BPh = tetraphenyl borate). DHT = dihexyl tartrate DBT = dibenzoyl tartrate PLA = poly (lactic acid). ...

The brush-type (Pirkle-type) CSPs have been used predominantly under normal phase conditions in LC. The chiral selector typically incorporates tt-acidic and/or n-basic functionality, and the chiral interactions between the analyte and the CSP include dipole-dipole interactions, n-n interactions, hydrogen bonding, and steric hindrance. The concept of reciprocity has been used to facilitate the rational design of chiral selectors having the desired selectivity [45]. 

The polymeric latex obtained in a hydrophobic organic solvent is poorly dispersed in water because of the presence of an emulsifier with a low HLB value. For this reason, a wetting agent is added to water or emulsion prior to the dissolution. The wetting agent (a surface active substance with a high HLB value) facilitates the inversion of latex phases to produce a direct type emulsion. Usually, it belongs to oxyethylated alkylphenols, fatty alcohols, or fatty acids. 

Fewer procedures have been explored recently for the synthesis of simple six-membered heterocycles by microwave-assisted MCRs. Libraries of 3,5,6-trisubstituted 2-pyridones have been prepared by the rapid solution phase three-component condensation of CH-acidic carbonyl compounds 44, NJ -dimethylformamide dimethyl acetal 45 and methylene active nitriles 47 imder microwave irradiation [77]. In this one-pot, two-step process for the synthesis of simple pyridones, initial condensation between 44 and 45 under solvent-free conditions was facilitated in 5 -10 min at either ambient temperature or 100 ° C by microwave irradiation, depending upon the CH-acidic carbonyl compound 44 used, to give enamine intermediate 46 (Scheme 19). Addition of the nitrile 47 and catalytic piperidine, and irradiation at 100 °C for 5 min, gave a library of 2-pyridones 48 in reasonable overall yield and high individual purities. 

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