Internal oxidizing agent

Two types of DGs are known (i) nonoxidizing and (ii) oxidising (DG ). In the case of the latter, they generally contain an N-O bond. Generally, the use of an internal oxidizing agent can lead to improved levels of reactivity and selectivity and also to a broader scope than in the case of external oxidants (this we will be discussed in the subsequent text). 

The product is considered nonhazardous for international transport purposes. However, it is an oxidizing agent sensitive to decomposition by water, direct sources of heat, catalysts, etc. Decomposition is accompanied by the Hberation of oxygen and heat which can support combustion and cause pressure bursts in confined spaces. Decomposition in the presence of organic material is rapid and highly exothermic. 

The hydrides can also be used to form primary alcohols from either terminal or internal olefins. The olefin and hydride form an alkenyl zirconium, Cp2ZrRCl, which is oxidized to the alcohol. Protonic oxidizing agents such as peroxides and peracids form the alcohol direcdy, but dry oxygen may also be used to form the alkoxide which can be hydrolyzed (234). 

The application of this type of ring formation to ene-l,4-dione systems necessitates either a formal internal oxidation, as in the examples in Scheme 52d (69CC420), or the use of a reducing agent (Schemes 52e (73TL5185) and 52f (65CC272)). 

Alkynes, like alkenes, can be cleaved by reaction with powerful oxidizing agents such as ozone or KMnC, although the reaction is of little value and we mention it only for completeness. A triple bond is generally less reactive than a double bond and yields of cleavage products are sometimes low. The products obtained from cleavage of an internal alkyne are carboxylic acids from a terminal alkyne, CO2 is formed as one product. 

The very rapid reaetion (3.15) with a large — AG can thus be measured. We therefore have an effective method for generating very rapidly in situ a powerful reducing or oxidizing agent. One of the most impressive applications of these properties is to the study of internal electron transfer in proteins. 

Another method used to deposit oxides, particularly those with a higher oxidation state than the starting cation, uses persulphate, S2O8, a strong oxidizing agent. While the exact mechanism of oxide formation using persulphate is unclear, it appears to involve internal electrochemical reactions e.g., for PbOz ... 

Terminal alkynes are prone to undergo facile oxidative cleavage to yield carboxylic acids with loss of the terminal carbon atom. In fact, most of the oxidizing agents that can be used in the selective oxidation of internal alkenes to 1,2-diketones [Ru04,711 PhIO with Ru catalysts,712 KMn04,713 T1(N03)3,716 0s04718] convert terminal alkynes to carboxylic acids. 

The product is considered nonhazardous for international transport puiposes. However, it is an oxidizing agent sensitive to decomposition by water, direct sources of heat, catalysts, etc,... 

For a better understanding of the factors that play a role in the catalytic selective reduction of nitrobenzene to nitrosobenzene some pieces of relevant information from previous work have to be considered. Favre et al.l6] found that oxides of various transition metals show catalytic activity in the mentioned reaction and a-Mn304 (Hausmannite) appeared to be the most active and selective catalyst. The function of nitrobenzene as an internal reducing agent has already been suggested by Zengell,] and is confirmed by Favre et al. Nitrobenzene can thus reduce as well as oxidize the catalyst... 

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