Chameleon oxidant

Although, as stated above, olefin epoxidation is commonly referred to as an electrophilic oxidation, recent theoretical calculations suggest that the electronic character of the oxygen transfer step needs to be considered to fully understand the mechanism [451]. The electronic character, that is, whether the oxidant acts as an electrophile or a nucleophile is studied by charge decomposition analysis (CDA) [452,453]. This analysis is a quantitative interpretation of the Dewar-Chatt-Dimcanson model and evaluates the relative importance of the orbital interactions between the olefin (donor) and the oxidant (acceptor) and vice versa [451]. For example, dimethyldioxirane (DMD) is described as a chameleon oxidant because in the oxidations of acrolein and acrylonitrile, it acts as a nucleophile [454]. In most cases though, epoxidation with peroxides occurs predominantly by electron donation from the 7t orbital of the olefin into the a orbital of the 0-0 bond in the transition state [455,456] (Fig. 1.10), so the oxidation is justifiably called an electrophilic process. 

De Visser, S.P., F. Ogliaro, P.K. Sharma, and S. Shaik (2002). Hydrogen bonding modulates the selectivity of enzymatic oxidation by P450 Chameleon oxidant behavior by Compound I. Angew. Chem. Int. Ed. 41. 1947-1951. 

Modulates the Selectivity of Enzymatic Oxidation by P450 A Chameleon Oxidant Behavior by Compound I. 

The phenomena enumerated in Section 2.4 do not, of course, fully describe all the differences between chemical and electrode processes of ion radical formation. From time to time, effects are found that cannot be clearly interpreted and categorized. For instance, one paper should be mentioned. It bears the symbolic title ir- and a-Diazo Radical Cations Electronic and Molecular Structure of a Chemical Chameleon (Bally et al. 1999). In this work, diphenyldiazomethane and its 15N2, 13C, and Di0 isotopomers, as well as the CH2-CH2 bridged derivative, 5-diazo-10,ll-dihydro-5H-dibenzo[a,d]cycloheptene, were ionized via one-electron electrolytic or chemical oxidation. Both reactions were performed in the same solvent (dichloromethane). Tetra-n-butylammonium tetrafluoroborate served as the supporting salt in the electrolysis. The chemical oxidation was carried out with tris(4-bromophenyl)-or tris(2,4-dibromophenyl)ammoniumyl hexachloroantimonates. Two distinct cation radicals that corresponded to it- and a-types were observed in both types of one-electron oxidation. These electromers are depicted in Scheme 2-28 for the case of diphenyldiazomethane. 

Perovskites — are a very large family of compounds with the crystal structure similar to that of (Ca, Sr) TiC>3 mineral, named after the Russian mineralogist T. A. Per-ovski (1792-1856). This structure is often called an inorganic chameleon due to the diversity of chemical compositions, structural modifications, and properties. Although most members of this family are oxidic compounds, some nitrides, carbides, halides, and hydrides also have this structure. 

Potassium Permanganate. Permanganic acid potassium salt chameleon mineral. KMnO mol wt 158.03. K 24.74%, Mn 34.76%, O 40.50%. Prepn from manganese ore by electrolytic oxidation Faith, Keyes Clark s Industrial Chemicals, F. A. Lowenheim, M. K. Moran, Eds. (Wiley-Interscience. New York, 4th ed., 1975) pp 679-683. 

Cpd I is a chameleon and two-state oxidant and as such exhibits TSR that can be tuned by the... 

Chameleonic features of carbenes can be further amplified by complexation with transition metals (Figure 5.42). In complexes with low valent/low oxidation state late transition metals (Fischer carbenes), carbenes display electrophilic properties, and often behave similarly to a carbonyl compound. Such carbenes also often have p-donor substituents, such as-OR or-NR, on the carbene carbon and x-acceptor ligands at the metal. In contrast, carbene complexes with high valent/high oxidation state early transition metals (Schrock carbenes) are nucleophilic. The ability of metal in the Schrock carbenes is further enhanced by donor ligands. 

Additionally, the film formation properties and outstanding mechanical properties of aramids make these polymers suitable for the production of organic light emitting diodes (OLEDs), and specifically polymer hght emitting diodes (PLEDs). Despite this, classical condensation polymers are rarely studied for these applications. Moreover, some luminescence materials also show electrochromism (EC), a phenomenon in which materials exhibit a reversible change in optical properties when they are oxidized and reduced. Electrochromic materials are now been exploited in diverse applications such as mirrors, displays, windows, and earth-tone chameleon materials [95]. 

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