Ethers oxygen atom

Multiple ether oxygen atoms can be present in the molecule. Cleavage and coupling reactions occur with direct fluorination although to a lesser extent than with ECF. This allows the direct fluorination of acid-sensitive materials, such as the formal shown below, which would not survive ECF (8). 

The C(ls) and 0(ls) spectra of polyphenylene ether (PPE) before and after evaporation of chromium onto the surface are shown in Fig. 23. C(ls) spectra of neat PPE consisted of two components, near 284.6 and 286.0 eV, that were assigned to carbon atoms in the benzene and methyl groups and in the ether groups, respectively. The 0(ls) spectrum consisted of a single peak, near 533.4 eV, that was assigned to the ether oxygen atoms. After evaporation of chromium, a new peak related to formation of Cr202 was observed near 531.0 eV. 

Zollinger and coworkers (Nakazumi et al., 1983) therefore supposed that the diazonium ion and the crown ether are in a rapid equilibrium with two complexes as in Scheme 11-2. One of these is the charge-transfer complex (CT), whose stability is based on the interaction between the acceptor (ArNj) and donor components (Crown). The acceptor center of the diazonium ion is either the (3-nitrogen atom or the combined 7r-electron system of the aryl part and the diazonio group, while the donor centers are one or more of the ether oxygen atoms. The other partner in the equilibrium is the insertion complex (IC), as shown in structure 11.5. Scheme 11-2 is intended to leave the question open as to whether the CT and IC complexes are formed competitively or consecutively from the components. ... 

DNA is a polymer with a backbone built of repeating units derived from the sugar ribose (20). For DNA, the ribose molecule has been modified by removing the oxygen atom at carbon atom 2, the second carbon atom clockwise from the ether oxygen atom in the five-membered ring. Therefore, the repeating unit—the monomer—is called deoxyribose (21). 

The phenyl ether oxygen atoms allow the two borazaphenanthrene rings to pivot with respect to each other, therefore this dimeric boronic acid anhydride can potentially exist in two isomeric forms, either face-to-face or helical (Fig. 18). In the face-to-face form the boron atoms of the bis(borazaphe-nanthrene) moieties have syn-orientation, while they have approximate anti-orientation in the helical form. Compound 68 has been characterized by X-ray crystallography in the helical form [109]. The dimensions of the cavity can be described by the transannular C C contacts between the carbon atoms in 2-position of the phenyl ether units, which have values of 5.12 and 6.21 A. 

In most other acids (see above), a low acidity is usually caused by the stabilization of the acidic form by intramolecular hydrogen bonds. However in the case of the acids [74] it is much less likely that the low acidity is caused by the stabilization of the acidic form because no ether oxygen atoms... 

Replacement of one of the ethereal oxygen atoms by a methylene group is compatible with anticoccidial activity. For example, condensation of substituted aniline 35 with dimethyl ethoxymethylenemalonate affords aminoacrylate 36. Thermal cyclization in diphenyl ether gives neguinate (37).11... 

In the older literature there are reports of colorless but conducting solutions of triarylmethyl derivatives. It seems well-established that triarylmethyl cations are colored, but an oxonium ion formed by the covalent attachment of a carbonium ion to an ether oxygen atom, for example, would be colorless. 

The formation of phenolic polymers by Claisen Rearrangement of poly(4-allyloxystyrenes) under acid catalyzed thermolysis conditions has previously been reported in connection with the development high resolution photoresists (14,15). This work was primarily focused on the production of soluble phenolic polymers that could be imaged on the basis of differential dissolution. In this regard, allyloxysty-rene polymers bearing alkyl substituents at the a-position to the ether oxygen atom... 

Crown ether complexes of bismuth nitrate were prepared by reacting Bi(N03)3 5H20 in 3 1 MeCN MeOH with a stoichiometric amount of the crown ether (101). Bi(N03)3(12-croum-4) has bismuth in a 10-coordinate Cs 4A,6B-expanded dodecahedral geometry 31, in which all four ether oxygen atoms are bound to the bismuth center... 

MeCN)][SbCl6]3 (106) have also been isolated. The dication has bismuth encompassed by the crown ether and bonded to all ether oxygen atoms, and the chlorine atom [Bi-Cl 2.479(6) A] and the pair of acetonitrile nitrogen atoms [Bi-N 2.82(2) and 2.86(3) A] are bound from the opposite side to the crown ether. The trication adopts a sandwich structure in which bismuth is bound to all four oxygen atoms of each crown ether [Bi-0 2.436(5) and 2.545(5) A]. The acetonitrile nitrogen atom occupies a position between the two ligands [Bi-N 2.650(9) A],... 

The compounds in a suitable solvent were subcutaneously injected into mice. Methyl fluoroacetate was always injected, under the same conditions, into a batch of mice as a control. The /9-carbon atom in /9-2-fluoroethoxypropionic acid and in /9-3-fluoropropoxypropionic acid is linked to the ether oxygen atom, and if/9-oxidation of these compounds takes place in vivo, the hydrogen carbonate of the fluoro alcohol is formed. One would expect this to have approximately the same toxicity as the alcohol itself, since the latter would be produced either by hydrolysis or by elimination of carbon dioxide ... 

The structure of a 1 2 complex of 18-crown-6 and benzenesulphonamide has been determined by x-ray (Knochel et al., 1978). It shows that the sulphonamide group is hydrogen-bonded to the crown-ether oxygen atoms. 

To illustrate the different complexities, CHARMM s energies arising from torsional terms depend only on the two central atoms, and there is only one cosine term. For MM2 and MM3, there are three cosine terms for each four-atom sequence that defines a torsion angle. MM2 treats lone pairs of electrons on hydroxyl and ether oxygen atoms as separate "atoms that also must be parameterized. Therefore, many more parameters must be used with the MM2 and MM3 programs than the CHARMM program. (The parameters for all the atomic sequences in glucose, and many other molecules, are furnished with MM2 and MM3.)... 

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