Solvents main

Sodium carboxymethylcellulose Na-CMC Water and polar organic solvents Main use where presence of moisture in solvent not a problem... 

With certain exceptions, primary fluorination of carbohydrate derivatives is very facile. Fluoride displacement of sulfonyloxy groups by potassium, or cesium, fluoride in 1,2-ethanediol and a variety of other solvents has frequently been used. Tetrabutylammonium (sometimes tetraethylammonium) fluoride in dipolar, aprotic solvents (mainly ace-... 

Two donor-acceptor systems were examined, with Coumarin 1 (Cl) and 9-aminoacridine (9AA) as donors and Rhodamine 6G (R6G) as the acceptor. Initial experiments were performed to compare the amount of transfer observed in bulk solution and in particles made of the same material. Glycerol was chosen as the solvent, mainly because of its low vapor pressure and high viscosity. The low vapor pressure was necessary so that particles would be relatively stable in size, and the high viscosity ensures that the excited donor is essentially stationary for the lifetime of the excited state. The concentrations used were chosen to minimize donor reabsorption and to make the extinction of the donor considerably larger than the extinction of the acceptor at the excitation wavelength. Excitation wavelengths of either 365 or 387 nm were used in the experiments. Concentration ratios, donor to acceptor, of 10 1 and... 

Generally, the solubihty characteristics of organic compounds depend on several properties of the participating components. For the solute, these properties are the molecular size and structure, polarity, dipole moment, va-por/sublimation pressure, and, in the case of a sohd solute, also its melting characteristics. When using SCCO2 as the solvent, mainly its dipole moment and quadrupole moment influence the solvatation process (Sect. 2.2). 

Since most of the EB is used for the manufacture of styrene, EB plants are usually found in close proximity to styrene plants. Very little EB is traded commercially or transported. A small amount of EB is used as a commercial solvent, mainly as a substitute for xylenes. 

Aurbach and co-workers performed a series of ex situ as well as in situ spectroscopic analyses on the surface of the working electrode upon which the cyclic voltammetry of electrolytes was carried out. On the basis of the functionalities detected in FT-IR, X-ray microanalysis, and nuclear magnetic resonance (NMR) studies, they were able to investigate the mechanisms involved in the reduction process of carbonate solvents and proposed that, upon reduction, these solvents mainly form lithium alkyl carbonates (RCOsLi), which are sensitive to various contaminants in the electrolyte system. For example, the presence of CO2 or trace moisture would cause the formation of Li2COs. This peculiar reduction product has been observed on all occasions when cyclic carbonates are present, and it seems to be independent of the nature of the working electrodes. A single electron mechanism has been shown for PC reduction in Scheme 1, while those of EC and linear carbonates are shown in Scheme 7. ... 

Significant progress has been achieved in the identification of poly sulfides in non-aqueous solvents, mainly by application of Raman spectroscopy. However, there are... 

In the oxide region of gold electrodes, residual lead can be present, resulting from irreversible adsorption, and presence of hydroxide species has been postulated ]265]. Pb UPD on Au(lll) has also been studied in selected organic solvents, mainly propylene carbonate [284]. Results similar to those in aqueous solutions have been obtained. Deposition of Pb on Au electrodes coated by silver has also been studied [285]. Depending on the silver layer thickness, results typical for Pb deposited on Au or Ag have been obtained. 

Water is the only solvent in which the composition of sugars has been systematically explored. Stevens1674 has determined the composition of several aldoses in pyridine-d5 by -n.m.r, spectroscopy at 300 MHz. There are scattered data on solutions in organic solvents (mainly pyridine, dimethyl sulfoxide, and N,N-dimethylformamide), but only rarely have four (or more) components of such solutions been quantitatively determined. The data that have been encountered are collected in Table VII undoubtedly, there are others that have been missed. 

Obviously, the condensation of a carbonyl group with a diol produces 1 mol of water and because of the reversibility of the reaction (hydrolysis of the acetal), yields are lowered if this by-product is not removed. For such a purpose, there are essentially two possibilities (1) the continuous removal of water by an azeotropic distillation with a solvent mainly chosen for its boiling point (petroleum ether, benzene, toluene, xylene, for instance) (2) the presence of a desiccant (the most commonly taken is copper(II)sulfate, but sodium sulfate or molecular sieves have been also used) molecules known to be water scavengers, such as ortho-esters or dialkylsulfites, have also been suggested, even if they are seldom used in carbohydrate chemistry. 

The extraction methods for aflatoxins are based on the solubility of these toxins in organic solvents, mainly chloroform, methanol, acetone, benzene, and acetonitrile. For more complex matrices, the addition of diatomaceous earth or citric acid is required. From matrices of vegetable origin, water is usually added in the extraction step, since it facilitates solvent penetration into substrates, improving the percentage of extraction of the toxin. 

In the case of solutions (liquid or solid mixtures), besides the molar fraction, we frequently use for expressing the solution composition the molar concentration (or molarity) ct, the number of moles for unit volume of the solution, and the molality mt, the number of moles for unit mass of the solvent (main component substance of the solution) ... 

We have studied the dispersibility of several pure PVAc-styrene graft copolymers with one PS branch in various selective solvents mainly at room temperature5. The experiment was done with two kinds of dried samples one was recovered from a tetrahydrofuran solution by pouring it into water and the other from a benzene solution which was poured into n-hexane. Let us refer to the former sample as A and the latter sample as B. Due to the difference in solubility of each polymer sequence in those solvents, sample A is supposed to have approximately such a microstructure that PVAc chains are extended and PS chains collapsed, while sample B has the inverse structure. A similar tendency was also pointed out by Merrett12. The results are summarized in Table 2. 

See Chapter 3 for more information about these solvents. Mainly perfluorobutyltehahydrofuran. 

Route a in Fig. 8 represents the case of modification in the substrate moiety caused by the presence of another reactive species, such as the solvent, participating in the reaction. An example of such an occurrence is afforded by aldehydes acting as substrates, which give the corresponding acetals 8 and 9 (Fig. 9) by reaction with ethanol, the solvent mainly used in Mannich synthesis. The expected Mannich base can however be obtained by further treatment of the acetal 9. - ... 

The values for H2O are usually smaller (that is, IAaSI, lACp ) than for other solvents mainly because of the large D value for H2O. 

The remaining wood components make up the fraction that can be extracted with different solvents, mainly comprising volatile and non-volatile acids, sugars, steroids, hydrolysable tannins (ellagitannins), volatile phenols, terpenes, lactones, etc. This review will deal with the volatile components that can leach out into the wine during barrel aging and as a result may affect the sensory attributes of wine. 

Byproducts in the aziridination reaction with ethoxycarbonyl nitrene were the carbamates formed by insertion of singlet nitrene into the C — H bonds of an alkene (mainly allylic C — H bonds) and hydrocarbon solvent (mainly tertiary C —H bonds)12 14. The formation of carbamates in the photochemical aziridination of cyclohexene was reduced by working at a low concentration of cyclohexene in dichloromethane14. 

The propagating anion and its counterion exist in relatively nonpolar solvents mainly in the form of associated ion pairs. Different kinds of ion pairs can be envisaged, depending on the extent of solvation of the ions. As a minimum, an equilibrium can be conceived between intimate (contact) ion pairs, solvent-separated ion pairs, and solvated unassociated ions. The nature of the reaction medium and counterion strongly influences the intimacy of ion association and the course of the polymerization. In some cases the niicrostructure of the polymer that is produced from a given monomer is also influenced by these variables. In hydrocarbon solvents, ion pairs are not solvated but they may exist as aggregates. Such inter-molecular association is not important in more polar media where the ion pairs can be solvated and perhaps even dissociated to some extent. 

Firstly, for rigid-chain polymas the excluded volume effects in thermodynamically good solvents (mainly determining the conformation and size of a flexible-chain molecule in solution are negligible. This has been confirmed both experimentally and theoretically ... 

The species are written without counter-ions for simplicity. It is known that these compounds exist in ether solvents mainly as ion-pairs. The relative reactivity of free anions and ion-pairs in these systems is not known. 

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