Water in solvents

Chemical tests for particular types of impurities, e.g. for peroxides in aliphatic ethers (with acidified KI), or for water in solvents (quantitatively by the Karl Fischer method, see Fieser and Fieser, Reagents for Organic Synthesis J. Wiley Sons, NY, Vol 1 pp. 353, 528, 1967, Library of Congress Catalog Card No 66-27894). 

L.A. Chen el, MP 23, 4-6(1928) CA 22, 3531(1928) (Detn of alcohol, ether and water in solvent eliminated from propellant during drying)... 

Table 1.4 Solvent descriptors of organic solvents commonly used for biocatalysis. Sw/o (solubility of water in solvent, wt%) So/w (solubility of solvent in water, wt%) and e (dielectric constant) values from [78], log P (P = partition coefficient between octanol and water), ET (empirical polarity parameter by Reichardt-Dimroth) and HS (Hildebrand solubility parameter, )l, cm J, ) from [79].

The detection of water in solvents, especially in trace quantities, can be troublesome. A method employing infrared spectrometry has been developed by Barbetta and Edgell for the detection of water in solvents at the submillimolar... 

Data for solvolyses of 1 -bromoadamantane (54, X = Br in Scheme 2.19) in ethanol-water in Table 2.3 show that S is approximately independent of solvent composition, but the selectivity is inverse. Why is S < 1 for competing nucleophilic substitutions when ethanol is normally more nucleophilic than water A credible explanation is that the products are formed by front-side collapse of a solvent-separated ion pair (52 in Scheme 2.18) - the caged structure prevents rear-side approach, so attack must occur from the front-side, and the proportion of water in solvent-separated ion pairs must be greater than in the bulk solvent. 

Figure 8.5. Determination of water in solvents, using Porapak Q porous polymer at 220°C. Courtesy of Varian Instruments.

Maximum solubility of water in solvent in g/L, except values in parentheses whi di are in g/kg means completely misdble with water - K... 

Despite the considerable coordinating ability of the water molecule (or CH3OH), other intermolecular associations sometimes take precedence under conditions where coordination to a metal ion would otherwise be expected. This is well-illustrated by the behavior of systems containing water in solvent quantities, as described in the preceding section. There also exist well-documented examples of related processes in which only stoichiometric amounts of water or related material are involved. 

Redox processes involving 178 have also been studied.Anodic oxidation of thianthrene has been eifected in a wide variety of solvents. Use of trifluoracetic acid gives stable solutions of 178 and, if perchloric acid is included, the solid perchlorate salt may be isolated on evaporation of the solvent after electrolysis. Dichloromethane at low temperatures has been used and, at the opposite extreme, fused aluminum chloride-sodium chloride mixtures. " Propylene carbonate permits the ready formation of 178, whereas the inclusion of water in solvent mixtures gives an electrochemical means of sulfoxidizing thianthrene. Reversible oxidation of 178 to thianthrenium dication may be brought about in customary solvents such as nitriles, nitro compounds, and dichloromethane if the solvent is treated with neutral alumina immediately before voltammetry addition of trifluoracetic anhydride to trifluoracetic acid equally ensures a water-free medium. The availability of anhydrous solvent systems which permit the reversible oxidation and reduction of 178 has enabled the determination of the equilibrium constants for the disproportionation of the radical and for its equilibria with other aromatic materials. ... 

In nonaqueous solutions the formation of oxide on the surface of silicon requires the presence of water. In solvents such as acetonitrile, nitromethane, and dimethyl sulfoxide, the HF-cleaned silicon surface gradually evolves from a H-terminated passive surface to a silicon oxide-covered surface due to the residual water (-lOpprn) present... 

Xw and xs< respectively, represent the mole-fraction solubility of water in solvent and solvent in water in the mutually saturated system. 

TABLE 93 S rinbilHy f Water in Solvente Used ta Nonnal-PhaM Chromatogni iky (21,22)... 

Solvent Solubility of Water in Solvent (gf) H-bonds H-acceptor H-donor Density (gmL ) Boiling Point ( O... 

The size of the water molecule is much less than that of all solvents and water molecules can therefore pack together. This manifests itself in the concentration of water in solvent being greater than that of solvent in water. 

Coefficient of expnnsion 55 C Flash point (Cleveland O C ) Freesing point Molecular weight Pounds per gallon 20 C Solubility in water 20 C Solubility of water in solvent 20 C Vapor pressure 20 C... 

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