Oxene

The product occurred in the form of pele yellow prisms end was insoluble in weter, ether, benzene, diluted elcohols, olive oil end chloroform, slightly soluble in ebsolute elcohol, di-oxene, tetrehydrofuren end ecetone, end soluble in dilute equeous ecids end elkelis. 

A pair of oxen pull a wooden plow through a muddy paddy field in Sri Lanka. (Corbis-Bettmann)... 

Langdon, J. (1986). Horses, Oxen and Technological Innovation. Cambridge, Eng. Cambridge University Press. 

The domestication of animals occurred at least 6000 years ago. Besides providing a reliable food source, domestic animals supplied energy for many purposes. Hitched to a plow, oxen or water buffalo allowed humans to cultivate larger parcels of land. Land travel over long distances became much easier with horses, camels, and even elephants. 

Filatov, M., Shaik, S., 1998b, Theoretical Investigation of Two-State-Reactivity Pathways of H-H Activation by FeO+ Addition-Elimination, Rebound , and Oxene-Insertion Mechanisms , J. Phys. Chem. A, 102, 3835. 

A 7r-bond can react with various active species, such as the electrophile oxene and its isoelec-tronic species (nitrenes and carbenes) and radicals. A 7r-bond can also react with a nucleophile, when it is conjugated with an electron-withdrawing group. In these reactions O, N, or C atom(s) are transferred from the active species to the olefins, forming two tr-bonds, such as C—O, C—N, and C—C, at the expense of the 7r-bond. If the 7r-bond is prochiral, chiral center(s) are... 

Metal-oxenoid (oxo metal) species and metal-nitrenoid (imino metal) species are isoelectronic and show similar reactivity both species can add to olefins and be inserted into C—H bonds. Naturally, the study of nitrene transfer reactions began with metalloporphyrins, which were originally used as the catalysts for oxene transfer reactions. 

If the active oxidizing agent is not formulated as a ferric oxene complex, the questions then remain as to what is its electronic ground state and how does hydrocarbon oxidation occur ... 

The ferric oxene complex (6) is, of course, just one resonance formulation of 5 (see scheme 2). Moreover, the addition of dioxygen and two electrons to P-450 is equivalent to using... 

To this end, cytochrome P-450 may be considered as nature s equivalent of Fenton s reagent in the enzyme system, highly reactive intermediates such as hydroxyl radicals and oxenes appear to be controlled by their interaction with hemoprotein. 

About a half-mile down the center road we saw another farmer driving a team of oxen. When we caught up with him, we got the same, routine. He would not answer German. 

Wilson RT (2003) The environmental ecology of oxen used for draught power. Agric Ecosys Environ 97 21-37... 

FIGURE 4.78 Mechanistic pathways for aromatic hydroxylation by concerted addition of oxene, pathway 1, or by stepwise addition of oxene, pathway 2. Pathways 2, 3, and 4 describe the formation of phenol that bypasses the arene oxide intermediate. 

As with an isolated double bond, epoxide formation in an aromatic ring, i.e., arene oxide formation, can occur mechanistically either by a concerted addition of oxene to form the arene oxide in a single step, pathway 1, or by a stepwise process, pathway 2 (Fig. 4.78). The stepwise process, pathway 2, would involve the initial addition of enzyme-bound Fe03+ to a specific carbon to form a tetrahedral intermediate, electron transfer from the aryl group to heme to form a carbonium ion adjacent to the oxygen adduct followed by... 

Figure 14.8. Radical versus concerted oxene transfer...

Although the Sharpless catalyst was extremely useful and efficient for allylic alcohols, the results with ordinary alkenes were very poor. Therefore the search for catalysts that would be enantioselective for non-alcoholic substrates continued. In 1990, the groups of Jacobsen and Katsuki reported on the enantioselective epoxidation of simple alkenes both using catalysts based on chiral manganese salen complexes [8,9], Since then the use of chiral salen complexes has been explored in a large number of reactions, which all utilise the Lewis acid character or the capacity of oxene, nitrene, or carbene transfer of the salen complexes (for a review see [10]). 

Biological systems have learned to generate and tame highly reactive chemical species such as NO, FT, 0 2, HO, and oxene, in other words to produce and trap them in nano-environments where they can react productively rather than deleteriously. But biological systems have also learned a contrasting strategy, which is to enhance the chemical reactivity of a mild molecule such as water. As illustrated in this book, a diversity of enzyme mechanisms have been discovered by nature to render water more nude-... 

The active metallic species is thought to be the oxene, Por—M=0 the mechanism is discussed in terms of the competing reactions of this species and the superior performance of the Fe(III) over the Mn(III) system is attributed to the faster oxygen transfer from the oxene to the sulfide or sulfoxide. 

The ferric peroxide intermediate could undergo either heterolytic or homolytic cleavage to give either a ferryl or diferryl oxene. In the path shown in Fig. 14, the organic radical is generated by reaction with the Fe center after heterolytic 0—0 bond cleavage. For RNRB2 this is the... 

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