Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Organic donor-acceptor properties

Theoretically, the purine- and pyrimidine-based nucleic acid constituents and the barbiturates have the potential to occur in several tautomeric forms of the keto/ enol and amino/imino type where the aromatic character of the six-membered pyrimidine ring is fully or, as in the barbiturates, partially retained, as illustrated in Fig. 15.4. In these molecular species, which are all feasible on the basis of organic chemical considerations, the hydrogen-bonding donor/acceptor properties of the functional amino, imino, enol and keto groups vary considerably, being donor in one form and acceptor in the other. [Pg.235]

W. Noll Spreading behaviour and acidolysis of the siloxane linkage as varying with the donor-acceptor properties of the organic substituents,... [Pg.477]

In accordance with donor-acceptor properties of organic compound, it interacts with the element-oxygen bond of oxide surface with an attack toward the Lewis base site (oxygen atom)... [Pg.242]

Acid-base properties of oxide surfaces are employed in many fields and their relationship with PZC has been often invoked. Adsorption and displacement of different organic molecules from gas phase was proposed as a tool to characterize acid-base properties of dry ZnO and MgO [341]. Hammet acidity functions were used as a measure of acid-base strength of oxides and some salts [342]. Acidity and basicity were determined by titration with 1-butylamine and trichloroacetic acid in benzene using indicators of different pAg. There is no simple correlation between these results and the PZC. Acid-base properties of surfaces have been derived from IR spectra of vapors of probe acids or bases, e.g. pyridine [343] adsorbed on these surfaces. The correlation between Gibbs energy of adsorption of organic solvents on oxides calculated from results obtained by means of inverse gas chromatography and the acceptor and donor ability of these solvents was too poor to use this method to characterize the donor-acceptor properties of the solids [344],... [Pg.222]

Labib, M.E. and Williams, R., The use of zeta-potential measurements in organic solvents to determine the donor-acceptor properties of solid surfaces, 7. Colloid Intetf. Sci., 91, 356, 1984. [Pg.1053]

In this section, following (29), we discuss the electrooptical properties of an asymmetric stack of organic donor-acceptor (D-A) interfaces. As we mentioned, the technological progress in molecular organic beam deposition is very fast and there is little doubt that a variety of such systems will be synthesized in the near future. With this in mind, we discuss the properties of a superlattice of... [Pg.315]

The versatility of silicon in organic chemistry has been attributed to its mildness as a metal5 to this should be added its dichotomous electron donor-acceptor properties. Under appropriate conditions proximate silicon groups can stabilize negative or positive charge and can strongly perturb the rc-system in a variety of molecules. [Pg.895]

In addition to forming hydrogen-bonded networks of the type discussed above, the donor-acceptor properties of carbohydrate hydroxy-groups facilitate the formation of complexes with simple organic bases. The complexes of this type which have been examined are the 1 1 adducts glucitol-... [Pg.344]

A qualitative study of the adsorption, in order to determine the functional group which takes part in the adsorption process, can be done by IR spectroscopy measurements. The OH stretching vibration of an hydroxylated siuface serves in prinicple as a spectroscopic probe of the molecular environment, and IR spectroscopy can be used to determine the chemical functionality and the donor acceptor properties of an oxide siuface upon adsorption of various probe molecules. Noller and Kladnig [22] found that the changes in the OH valence frequency values (Av values), upon adsorption of a variety of organic donor molecules on to acidic silica, were linearly related to the donor number of the adsorbate. [Pg.309]

Charge-transfer adducts are formed with the gold(I) trimers [Au3(MeN=COR)3] (R = Me, Et), which act as electron donors, and organic electron acceptors as nitro-9-fluorenes. The structures of these adducts involve mixed stacks in which the gold trimers and the planar nitro-fluorenes are interleaved.3130 No luminescence has been observed from these solid charge-transfer adducts, which is not surprising since the luminescence of [Au3(MeN=COR)3] is a property that is associated with the supramolecular organization in the solid. [Pg.1076]

Diorganoboryloxides, R2BO, bearing bulky organic substituents are quasi-alkoxide ligands for main group and transition metals. Because of the 7r-acceptor properties of boron, these anions are weaker 7r-donors than alkoxides, and this is reflected in their structural chemistry. Diethylzinc reacted with the borinic anhydride (9-BBN)20, Scheme 82, to afford the alkylzincboryloxide [EtZnO(9-BBN)]4 129, which also crystallizes in heterocubic form.187... [Pg.367]

Senesi and Testini [147,156] and Senesi et al. [150,153] showed by ESR the interaction of HA from different sources with a number of substituted urea herbicides by electron donor-acceptor processes involves organic free radicals which lead to the formation of charge-transfer complexes. The chemical structures and properties of the substituted urea herbicides influence the extent of formation of electron donor-acceptor systems with HA. Substituted ureas are, in fact, expected to act as electron donors from the nitrogen (or oxygen) atoms to electron acceptor sites on quinone or similar units in HA molecules. [Pg.136]

All these data verify that in real systems, the rate of electron transfer between components of a conductive chain is high. There are states of a mixed valence. Enhanced electric conductivity and other unusual physical properties are widespread among those inorganic or coordination compounds that contain metals in intermediate -valence states. In cases of organic metals, nonstoi-chiometric donor/acceptor ratios provide even better results. For example, the salt of (TTF)i (Br)oj composition displays an electric conductivity of 2 X 10 cm while (TTF)i(Br)i salt does not... [Pg.416]


See other pages where Organic donor-acceptor properties is mentioned: [Pg.2]    [Pg.149]    [Pg.133]    [Pg.130]    [Pg.801]    [Pg.4]    [Pg.456]    [Pg.321]    [Pg.176]    [Pg.26]    [Pg.205]    [Pg.332]    [Pg.768]    [Pg.113]    [Pg.76]    [Pg.287]    [Pg.317]    [Pg.4]    [Pg.309]    [Pg.139]    [Pg.318]    [Pg.393]    [Pg.175]    [Pg.12]    [Pg.380]    [Pg.148]    [Pg.233]    [Pg.218]    [Pg.453]    [Pg.50]    [Pg.251]    [Pg.443]    [Pg.85]    [Pg.345]    [Pg.147]    [Pg.28]    [Pg.193]   
See also in sourсe #XX -- [ Pg.76 ]




SEARCH



Acceptor properties

Donor properties

Donor/acceptor organizations

Organ donors

Organic acceptor

Organic donors

Properties donor-acceptor

© 2024 chempedia.info