Polyethylene glycol transformations

It was noted early by Smid and his coworkers that open-chained polyethylene glycol type compounds bind alkali metals much as the crowns do, but with considerably lower binding constants. This suggested that such materials could be substituted for crown ethers in phase transfer catalytic reactions where a larger amount of the more economical material could effect the transformation just as effectively as more expensive cyclic ethers. Knbchel and coworkers demonstrated the application of open-chained crown ether equivalents in 1975 . Recently, a number of applications have been published in which simple polyethylene glycols are substituted for crowns . These include nucleophilic substitution reactions, as well as solubilization of arenediazonium cations . Glymes have also been bound into polymer backbones for use as catalysts " " . 

Accelerated aging and crystal transformation rates have also been traced to high residual moisture content. Ando et al. studied the effect of moisture content on the crystallization of anhydrous theophylline in tablets [9]. Their results also indicate that anhydrous materials convert to hydrates at high levels of relative humidity. In addition, if hygroscopic materials (e.g., polyethylene glycol 6000) are also contained in the formulation, needle-like crystals form at the tablet surface and significantly reduce the release rate of the theophylline. 

Gietz, R. D., and Woods, R. A. (2002). Transformation of yeast by lithium acetate/single-stranded carrier DNA/polyethylene glycol method. Methods Enzymol. 350, 87-96. 

Polyethylene glycols and their monomethyl ethers are inexpensive, thermally stable, recoverable, and nontoxic, and can be used as green solvents for various transformations [82] including Knoevenagel condensations [83-85]. 

Different kinds of alkyl and aryl sulfonates 7 have been transformed to the fluorides 8 under fairly mild conditions with potassium fluoride in polyethylene glycol 400.145 No trace of elimination products, normally found due to attack of a second mole of potassium fluoride on the fluoroalkane eliminating hydrogen fluoride, is observed and the hydrolysis product is present only in 4% yield. No displacement of the tosylate group occurred for neopentyl tosylate. 

Laser desorption Fourier transform mass spectrometry (LD-FTMS) results from a series of peptides and polymers are presented. Successful production of molecular ions of peptides with masses up to 2000 amu is demonstrated. The amount of structurally useful fragmentation diminishes rapidly with increasing mass. Preliminary results of laser photodissociation experiments in an attempt to increase the available structural information are also presented. The synthetic biopolymer poly(phenylalanine) is used as a model for higher molecular weight peptides and produces ions approaching m/z 4000. Current instrument resolution limits are demonstrated utilizing a polyethylene-glycol) polymer, with unit mass resolution obtainable to almost 4000 amu. 

Keywords Carbon dioxide Polyethylene glycol C02 transformation Cyclic carbonates Dimethylcarbonate Oxazolidinones Organic carbamates Urea derivatives... 

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