Ethylene glycol units

Cychc polyethers, or crown ethers, are cycHc stmctures containing ethylene glycol units as 2 2 >n n > 2 and generally between 4... 

Vicinal hydroxyl groups, as in an ethylene glycol unit, have conformational attributes that can be described by using acyclic orientational notation... 

With the a-CD-PEG complexes isolated by filtration or centrifugation, the yields of complexes were determined as a function of PEG molecular weight, assuming that two ethylene glycol units are bound to one a-CD, i.e., the stoichiometric ratio is 2 1, and the results shown in Fig. 3 were obtained. It is... 

Though y-CD was found to form complexes also with PEG, the yields were too small for their characterization. Thus, Harada et al. turned to two PEG deriva-tives-bis(3,5-dinitrobenzoyl)-PEG (PEG-DNB2) and bis(2,4-dinitrophenyl-amino)-PEG (PEG-DNP2)-, which were found to complex with this CD at high yields. Using a fluorescent probe technique the resulting complexes were shown to include four ethylene glycol units in one y-CD cavity. However, these PEG derivatives formed no complex with a-CD. This is attributable to the fact that their chains are too thick to enter the slim a-CD cavity. 

In order to work out in more detail Harada and coworkers took a step further by preparing fluorescence-labeled bis(l-naphthylacetyl)-PEG (PEG-1N2) and bis(2-naphthylacetyl)-PEG (PEG-2N2). The complexes of these compounds with y-CD were isolated by standard methods and subjected to NMR measurement. The results also conformed to the conclusion that four ethylene glycol units are included in one y-CD. 

In passing, we again touch upon some geometrical facts. The diameter of the y-CD is 8.5o-9 A, which is about twice as large as that of the a-CD. The cavity depth is 7 A for all a, ft and y-CD, and almost equals the length of two ethylene glycol units. Molecular models show that the y-CD cavity is wide enough to accommodate two PEG chains, but the a-CD cavity is too narrow to make this possible. 

Polyrotaxane Molecular weightb Number of ethylene glycol units (included + non-included) Number of threaded a-CDb Molar ratio of ethylene glycol units to a-CD... 

As discussed for biphenol-based phosphites, phosphites derived from ClMeO-biphenol should also be sterically more demanding and have an increased ring size as compared to catechol-based phosphites. Moreover, by comparing the catalytic results of biphenol- and ClMeO-biphenol-based ligands, conclusions on the influence of the substitution pattern and resulting electronic effects on the activity and selectivity in the hydroformylation can be drawn. Therefore, ClMeO-biphenol-based phosphites with PEG side chains consisting of one to three ethylene glycol units were included in the present study. 

More recently, Pearce and Heydeman suggested non-oxidative removal of ethylene glycol units as acetaldehyde by a membrane-bound, oxygen-sensitive enzyme of a novel type, i.e., diethylene glycol lyase (18). Schoberl suggested that PEG was catabolized by Ci step, liberating formate which was metabolized by a serine pathway (19). 

Incorporation of the Dibenzofuran-4,6-dipropanoic Acid Template with Intervening Ethylene Glycol Units Between the Template and Peptide Strands... 

The chiral crown ethers 101,102,104,105, and 152, andpodands 100 and 153 were formed from isomannide by introducing ethylene glycol units as... 

In order to get more detailed information about the motions associated with the p relaxation in PET and to understand the differences observed between mechanical and dielectric data, 13 C NMR was used, as well as 2H NMR on PET samples selectively deuterated either on the phenyl rings or on the ethylene glycol units [12]. Due to the higher frequency range corresponding to NMR experiments (105 Hz), the extrapolation of the dielectric results leads to the occurrence of the motions involved in the f3 relaxation around 25 °C, which is effectively observed. 

FIG. 14 Platelet adhesion to the PU films grafted with methoxy polyethylene glycol) methacrylates at different concentrations of chain transfer agent (c-cysteine). Ethylene glycol units in monomers ( ) 4, (O) 9, and ( ) 23. (From Ref. 74.)... 

Most of the supramolecular assemblies have been constructed from the solutions of each component. More recently, the authors found that CD formed inclusion complexes with PEG with high selectivity only by mixing powdered crystals of CDs and polymer samples without any solvents under ambient conditions (Scheme 2) [120]. When crystals of a-CD and PEG (Mw = 400) were mixed without solvent (a-CD ethylene glycol unit =1 2), the X-ray powder patterns changed a peak at 26 = 22° characteristic for the cage type decreased, and a peak at 26 = 20° characteristic for the channel type appeared... 

First, the authors prepared PEG with an anthracene group at one end of the polymer chain. Then, the modified polymer was treated with a-CD to formp5eudo-polyrotaxane. Finally, the p5eudo-polyrotaxane was capped with 9-anthracene carboxylic acid to obtain polyrotaxane (Scheme 10). The ratio of CD and monomer units was found to be 4 1 (ethylene glycol unit CD) by NMR. When a DMSO solution of a-CD-polyrotaxane was irradiated with visible fight (A > 340 nm) (500 W Xe lamp with UV cut filter) under argon, poly(Q -CD-polyrotaxane) was precipitated out. The NMR spectrum of the product showed broad resonance bands due to a-CD and PEG and the absence of the absorption bands due to monomeric 9-anthracene. Characteristic absorption and emission bands due to monomeric 9-anthracene have completely disappeared. 

Carbohydrate crown ethers were obtained with ethylene spacers from a crown ether point of view, the carbohydrate vicinal diols are replacing one ethylene glycol unit [181,182], Cyclic compounds synthesized include bis-gluco-15-crown-5 82, bis-gluco-21-crown-7, and tetra-gluco-24-crown-8 (O Scheme 14). These chiral macrocycles could serve as catalysts in the asymmetric Michael addition of methyl a-phenylacetate to methyl acrylate. With the goal to study molecular interactions, P,P, and Q, Q -bis-maltosides with aliphatic two-, three-, or four-earbon spacers were synthesized [183]. Spaced cyclodextrins were prepared to study their supramolecular properties [184,185]. 

Compound 5 was built with a relatively long PEG spacer arm of defined length (12 ethylene glycol units) (25). The purpose was to provide an optimal accessibility of the liposomal mannose ligands to their receptors (28). However, the PEG spacer arm length can be changed if needed, e.g., for stealth vesicles. 

In the procedures below, methodology is described to facilitate medium scale (ca. 100 g) synthesis of a main-chain thermotropic liquid crystalline polymer containing ethylene glycol units as a flexible spacer between the rigid aromatic units. Two methods are described melt polymerization, and polymerization in a heat-transfer solvent with an inorganic medium (Claytone). For melt polymerization, the material is obtained as an extremely rigid solid, while in the... 

Aerosol OT (sodium diethylhexylsulfosuccinate) Didodecyldimethylammonium bromide Nonionic surfactant of the polyethylene glycol alkyl ether type the alkyl chain contains i carbon atoms and the polar group j ethylene glycol units Critical micelle concentration... 

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