Ethylene derivatives glycols, preferential

Lithium perchlorate/calcium carbonate Ring expansion of isocyclic diol monotosylates with preceding preferential formation of glycols from ethylene derivatives and preferential O-tosylation... 

Osmium tetroxide pyridine sodium hydrogen sulfite Glycols from ethylene derivatives Preferential formation... 

Difluoropyridines. 2,4-Difluoropyridine can be prepared (26% yield) from 2,4-dichloropyridine and potassium fluoride in sulfolane and ethylene glycol initiator (403). The 4-fluorine is preferentially replaced by oxygen nucleophiles to give 2-fluoro-4-hydroxypyridine derivatives for herbicidal apphcations (404). 

Unsubstituted 20-ketones undergo exchange dioxolanation nearly with the same ease as saturated 3-ketones although preferential ketalization at C-3 can be achieved under these conditions. " 20,20-Cycloethylenedioxy derivatives are readily prepared by acid-catalyzed reaction with ethylene glycol. The presence of a 12-ketone inhibits formation of 20-ketals. Selective removal of 20-ketals in the presence of a 3-ketal is effected with boron trifluoride at room temperature. Hemithioketals and thioketals " are obtained by conventional procedures. However, the 20-thioketal does not form under mild conditions (dilution technique). ... 

If the metallisable dye is insoluble in water, a miscible solvent such as ethanol or ethylene glycol may be added. Polar solvents such as formamide or molten urea have sometimes been preferred. It is likely that such solvents will preferentially displace water molecules and coordinate with the chromium (III) ion as the first step in the reaction. If colourless organic chelates of chromium, such as those derived from oxalic or tartaric acid, are used instead of or in addition to hydrated chromium (III) salts, the difficulty of replacing the strongly coordinated water molecules in the first stage of the reaction is eliminated. In this way the initial reaction can be carried out at high pH without contamination by the precipitation of chromium hydroxide. Use of the complex ammonium chromisalicylate (5.12) in this connection should also be noted (section 5.4-1). 

The solvent and ion selectivity behavior of Na+ and K+ forms of Linde A have been measured in nonaqueous and mixed media. An osmotic pressure model accurately describes ion exchange in concentrated aqueous electrolyte solutions and is extended to solvent selectivity in mixed media. Water is preferentially adsorbed over alcohols, and ethylene glycol is preferred over ethanol in accord with the derived equation... 

Figure 2.17a shows an example of the neutron scattering that results when DjO is preferentially absorbed by one segment in a polymer. These data were obtained from a polymer in which poly(ethylene glycol), PEG, segments are randomly inserted along the polymer chains composed mostly of hydrophobic groups, tyrosine-derived polycarbonates... 

---