Glycol, model structure

The mobilities of alkylpyridines were modeled and predicted in capillary zone electrophoresis.35 The model predicted that compounds adopt a preferred orientation, and additionally predicted mobilities of structural isomers to within 4%, a higher degree of accuracy than can be obtained from simple considerations of van der Waal s radius. Quantitative prediction of the mobilities of some pyridines, such as alkenylpyridines, was not possible. Mobilities of small solutes in capillaries filled with oligomers of ethylene glycol were related to solution viscosity and the diffusion coefficient.36... 

Fig. 9.2.7 Characterization of the intermediate phase obtained in the reduction of Ni(OH)2 in ethylene glycol (a) x-ray diffraction pattern, and (b) structural model. (From Ref. 29.)...

Authors give a short description of a RIS model developed for polylpropylene glycol terephthalate), PPT. This model is based on the known RIS models for PET. Statistical weight parameters and torsion angles of the chain are discussed. Simple scrutiny of structural characteristics of PPT chains indicate that certain conformations that are accessible in PET are suppressed in PPT. In this work, the dipole moment of these chains and its temperature coefficient are measured and the results compared with those calculated using statistical mechanics. A comparative study of the polarity of PPT and PET is also made. 

Similar calculations were conducted also for the analogous glycolate complexes, using the hydrido complex 74 as model (Figure 9)30a. The calculations confirmed the ground state structure (I) established for similar compounds in the solid state. The diastereomeric TBP structures II and III, as well as the distorted SP structures IV and V, were calculated... 

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. 

Herrmann and co-workers synthesized [Os(0)(Me)4] from 0s04 and dimethylzinc or methyltris(isopropoxy)titanium (180). An alternative route is by methylation of the glycolate osmium(VI) complex [0=0s(0CH2CH26)2] with dimethylzinc (180). The thermally labile ethyl derivative [Os(0)(Et)4] has also been prepared (180). [Os(0)(Me)4] is an orange, air-stable, volatile, crystalline compound that melts at 74°C without decomposition. The gas-phase average molecular structure of [Os(0)(Me)4], determined by electron diffraction techniques, is consistent with a theoretical model of C4 symmetry with d(Os—C) = 2.096(3) A, d(0s=0) = 1.681(4) A, and ZO—Os—C = 112.2(5)° (180). Cyclic voltammetric studies showed that [Os(0)(Me)4] undergoes reversible reduction at - 1.58 V and an irreversible oxidation at -f 2.2 V vs Ag/AgCl in MeCN. 

Figure 10.1 Temperature dependence of the H T2 relaxation time of well-defined end-linked (PPO) networks with narrow molecular mass distributions between chemical crosslinks [44], The molecular mass of network chains (in g/mol) is shown in this figure. The temperature dependence of a linear, high-molecular-mass polypropylene oxide) prepared from a polypropylene glycol precursor (with a molecular mass of 4000 g/mol) using a chain extender with a chemical structure similar to that of the crosslinker is shown for comparison. The synthesis of the model networks has been...

As explained previously, electrodissolution in ionic liquids is a simple and efficient process, particularly in chloride-based eutectics. Type III eutectics based on hydrogen bond donors are particularly suitable for this purpose. However, it has been noted that the polishing process only occurs in very specific liquids and even structurally related compounds are often not effective. It has been shown that 316 series stainless steels can be electropolished in choline chloride ethylene glycol eutectics [19] and extensive electrochemical studies have been carried out. The dissolution process in aqueous solutions has been described by two main models the duplex salt model, which describes a compact and porous layer at the iron surface [20], and an adsorbate-acceptor mechanism, which looks at the role of adsorbed metallic species and the transport of the acceptor which solubilises... 

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