Solvent effects without added water

An examination of solvent effects on reverse micelles without added water provides even greater insight into the results for C11-14 EO5. The solvent effect on the aggregation number of dry alkali dinonylnaphthalenesulfonates was studied in a classic paper by Little and Singleterry (2). For sodium as the counterion, the... 

Although supercritical CO2 is an effective solvent for oils, fats, and similar substances, it is a poor one for nonvolatile hydrophilic (water-loving) substances such as proteins or metallic salts. Adding water as such to the supercritical CO2 is of little help, as the solubility of water in it is limited. Johnson and co-workers216 overcame the latter limitation by forming water-in-C02 emulsions with the aid of an added nontoxic perfluoropolyether surfactant that forms reverse micelles around the water microdroplets, in effect combining the special properties of supercritical CO2 with the solvent power of water. These emulsions can dissolve a variety of biomolecules at near-ambient temperatures, without loss of their biological activity. 

Miwa and Yamamoto (31) described a simple and rapid method with high accuracy and reliability for the determination of C8 0-C22 6 fatty acids, which occur in esterified forms in dietary fats and oils and in living cells [the biological effects of routinely consumed fats and oils are of wide interest because of their impact on human health and nutrition (28,29), in particular, the ratio of cu-3 polyunsaturated fatty acid to w-6 polyunsaturated fatty acids (w-3/cu-6) seems to be associated with atherosclerosis and breast and colon cancers (30)]. They report improved separation of 29 saturated and mono- and polyunsaturated fatty acids (C8-C22), including cis-trans isomers and double-bond positional isomers, as hydrazides formed by direct derivatization with 2-nitrophenylhydrazine hydrochloride (2-NPH HC1) of saponified samples without extraction. The column consisted of a J sphere ODS-M 80 column (particle size 4 /xm, 250 X 4.6-mm ID), packed closely with spherical silica encapsulated to reach a carbon content of about 14% with end-capped octadecyl-bonded-spherical silica (ODS), maintained at 50°C. The solvent system was acetonitrile-water (86 14, v/v) maintained at pH 4-5 by adding 0.1 M hydrochloric acid with a flow rate of 2.0 ml/min. Separation was performed within only 22 min by a simple isocratic elution (Fig. 6). The resolution of double-bond positional isomers, such as y-linolenic ( >-6) and a-linolenic acid ( >-3) hydrazides and w-9, >-12, and >-15 eicosenoic acid hydrazides was achieved by use of this column. 

It would be useful to have liquid present in the polymerization reactor that provided the advantages of a solvent but without any of the disadvantages. Sound unlikely How about water One technique, called suspension polymerization, involves adding monomer to water in a reactor, agitating the mixture rapidly so that the monomer breaks apart into very small droplets, adding an initiator that is soluble in the monomer, and heating. Each droplet acts as a microbulk polymerization, the water very effectively removes the heat of polymerization, and the resulting polymer spheres are easily separated and filtered. This process, also known as bead polymeriza-... 

Moreover, adding small amounts of water to the solvent had no apparent effect on the spin label s mobility, as evidenced by the spectra in Figure 2. EPR spectra recorded in butyl acetate with and without 1% water revealed that the active site conformation was unchanged by water addition even though the enzyme s activity was much higher when 1% water was present. Thus, the increase in activity upon water addition cannot be attributed to a loosening up of the active-site conformation. This result differs from a proposed model of the sequential hydration of dry lysozyme (19), in which restoration of enzyme activity followed a hydration-induced flexibility increase. 

Lubineau and Aug reported the beneficial effect of using water as the solvent in the Michael addition of nitroalkanes to methyl vinyl ketone under neutral conditions. Moreover, addition of glucose or saccharose increased the rate of the reaction. Various nitroalkanes were condensed with different electrophilic alkenes in NaOH (0.025-0.1 m), without any added organic solvent, affording the corresponding adducts with moderate to good yields when a catalytic amoimt of cetyltrimethylammonium chloride (CTACl) was used (Scheme 8.12). ... 

It has been shown that a definite association complex is formed between and PEO in methanol. This complex has not been detected in KI-PEO-water solutions. One can reasonably seek to explain the observed differences in relaxation behavior in terms of this complex. We pursue this hypothesis in subsequent paragraphs. Alternatively, the effect of KI on the two solvents must be considered. One could speculate that the added salt drastically changes the solution viscosity of methanol, through ion-solvent interactions, without interacting with PEO. Under these circumstances, a... 

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