Protons, mobile ethers with

Pentaethoxyuranium is a dark-brown, mobile liquid with a density of 1.71 g/cm3 at 25°.2 The liquid boils at 123° at 0.001 torr and is thermally stable below 170°. The compound is readily hydrolyzed and is oxidized by dry oxygen (in the presence of excess NaOC2Hs) to hexaethoxyuranium.2 Pentaethoxyuranium has a dimeric structure at room temperature as determined by freezing-point depression measurements in benzene.2 It is miscible with ethanol, diethyl ether, benzene, petroleum ether, ethyl acetate, carbon tetrachloride, chloroform, carbon disulfide, pyridine, dioxane, and nitrobenzene. The proton magnetic... 

The fact that NH2—PTM- can be obtained from NH2—PTM—H in the conventional manner (DMSO/ether) in abnormally low yield suggests that the proton mobilities of NHj and CH are comparable. Presumably, the formation of "NH—PTM—H is responsible for the low yield, since by oxidation with I... 

Reactions of ethers with a mobile proton Cleavage of ketones, rearrangement to alcohols s. 16, 763 ... 

Reactions of ethers with a mobile proton Cleavage to ketones... 

Although the majority of reports of macrocycles in analytical chromatography have involved ligand association with the stationary phase, their use as mobile phase constituents has also been investigated. Lamb and Drake [11] showed that addition of water-soluble crown ethers to the mobile phase altered the retention of alkali metal cations on an underivatized reversed phase column. Nakagawa et al. [63-66] also used crown ether-containing mobile phases in the separation of protonated amines, amino acids and peptides, and [1-lactam antibiotics. 

The mobile phases used in normal-phase chromatography are based on nonpolar hydrocarbons, such as hexane, heptane, or octane, to which is added a small amount of a more polar solvent, such as 2-propanol.5 Solvent selectivity is controlled by the nature of the added solvent. Additives with large dipole moments, such as methylene chloride and 1,2-dichlor-oethane, interact preferentially with solutes that have large dipole moments, such as nitro- compounds, nitriles, amines, and sulfoxides. Good proton donors such as chloroform, m-cresol, and water interact preferentially with basic solutes such as amines and sulfoxides, whereas good proton acceptors such as alcohols, ethers, and amines tend to interact best with hydroxylated molecules such as acids and phenols. A variety of solvents used as mobile phases in normal-phase chromatography are listed in Table 2.2, some of which may need to be stabilized by addition of an antioxidant, such as 3-5% ethanol, because of the propensity for peroxide formation. 

PDE5 inhibitor (Fig. 8.17). The anal)d e and internal standard (sildenafil, II) were extracted by liquid-liquid extraction with diethyl ether/dichlor-omethane (70 /30, v/v) using a Glas-Col Multi-Pulse Vortexer. The chromatographic separation was performed on reverse phase Xterra MS C18 column with a mobile phase of 10 mM ammonium formate/acetonitrile (10/90, v/v, pH adjusted to 3.0 with formic acid). The protonate of analyte was quantitated in positive ionization by MRM with a mass spectrometer. The mass transitions m/z 390.4 > 268.0 and m/z 475.5 > 58.3 were used to measure I and II, respectively. The assay... 

These macrocyclic ethers assume a crown-like shape in solution with a central cavity capable of containing a small solute. They bind to small cationic species through association with the electron-rich oxygens of the ether linkage. Chiral crown ethers (Fig. 31) serve as selectors for enantiomeric amines in the protonated state. They have been used as mobile-phase... 

---