Oligo protonation

Kemkes256 assumes that the overall order relative to the esterification of terephthalic acid by 1,2-ethanediol in oligo(l,2-ethanediyl terephthalate) is two no mechanism has however been suggested. Mares257 considers that during the esterification of terephthalic acid with 1,2-ethanediol, two parallel kinetic paths take place, one corresponding to a reaction catalyzed by non-dissociated add and the other to a non-catalyzed process. In fact, Mares257 is reserved about the existence of protonic catalysis. Some other orders were found for the system terephthalic atid/l,2-ethanediol 0 (overall)318 2 (add) andO (alcohol)203 1 (add) and 1 (alcohol)181 1 (add)194 . These contradictory results could be partly due to the low solubility of terephthalic acid in 1,2-ethanediol. 

When neither solvent nor supporting salt can provide oxygen (e.g. in a system CH2CI2/BU4NBF4) and a strong proton donor is present in the solution, the oxidation of diphenylsulfide yields oligo(p-phenylene)sulfides (Scheme 28) [122],... 

Electron and Hole Transfer from the Hydration Layer to DNA. - Debije et al. investigated the transfer of X-radiation-induced electrons and holes (H20 +) from the hydration layer of crystalline oligonucleotides into the oligo itself.57 Results from these Q-band ESR experiments at 4 K suggest that ionization of hydration water results in both electron and hole transfer to the DNA model structures. The proton transfer reaction from H20 + to form the hydroxyl radical occurs on the timescale of a few molecular vibrations, thus it limits hole transfer distance from a water hole to DNA. 

N. K. Kochetkov, O. S. Chizhov, and A. S. Shashkov, Dependence of 13C chemical shifts on the spatial interaction of protons, and its application in structural and conformational studies of oligo- and poly-saccharides, Carbohydr. Res., 133 (1984) 173-185. 

Some of the extensive experimental data on the one-bond carbon-proton coupling constants in several pyranose derivatives, as well as oligo- and polysaccharides, are summarized in Tables I-V. Several generalizations may be made from inspection of these data. The anomer that has an equatorially disposed hydrogen at C-1 has the larger coupling constant, and the value in such pyranosides is in... 

The most important, practical application of 13C-n.m.r. spectroscopy is probably the simple characterization and identification of organic compounds. Because of the simplicity of proton-decoupled carbon spectra, and the sensitivity of carbon-13 chemical-shifts towards structural changes, carbon spectra are extremely well suited for this purpose (see, for example, Ref. 84), and it is for this reason that the emphasis of the present article has been placed on presenting chemical-shift data of monosaccharides and their derivatives. Such data are also important for structural studies of oligo- and poly-saccharides,3 and for the investigation of such mixtures as those arising from mutarotation85-87 (see Section 11,4) or from other reactions.34... 

Matile reported poor bilayer solubility of rigid-rod 9 so tackled this problem by incorporating lateral propylene side chains.35c This was expected to increase lipophilicity and also to improve the flexibility of the hydroxyl groups thus facilitating proton transport by the HBC mechanism. The structural modifications did not appear to have a detrimental effect on the active structure and increased ion flux rates were seen for the propylene-substituted oligo(phenylenes). 

The ability of adenine and cytosine to undergo reduction in aqueous medium is at least partially retained at the level of oligo- and polynucleotides. In both acid and neutral media, such residues in single-stranded RNA, DNA and synthetic polynucleotides, when subjected to d.c. polarography, undergo irreversible reduction in a protonated, adsorbed, state with the transfer of four electrons to adenine... 

After the development of the electrolytic reductive coupling of acrylonitrile to adiponitrile (Chapter 21), many investigations have been directed toward developing an alternative, indirect electrolytic process. The electrolytic hydrodimerization reaction in neutral solution [32,33] is critically dependent on the proton activity at the electrode. If the proton activity is too high, the product is predominantly propionitrile, whereas oligo-or polymerization occurs at too low a proton activity. The establishment of a reaction layer with a suitable proton activity in which conditions are favorable for a hydrodimerization of acrylonitrile to adiponitrile is, thus, of paramount importance. This can be accomplished in different ways. 

It cannot be excluded that the back biting depicted in Scheme 10 could be responsible for the observed absence of methyl proton.389 Scheme 10 would leave most of the dead polymer molecules without methyl end groups. The chemical shifts of the vinylic protons in the resulting oligo-acrylamides are at 5.75 and 6.25 ppm, which is similar to the methacrylate end group of polyBA which has been terminated by back biting. In oligo-acrylates produced by CCT, the vinylic protons have resonances at 6.8 and 5.85 ppm.383 The mechanism of Scheme 11 in acrylate polymerization requires additional study. 

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