Peroxidative halogenations

Oxidation with Oxygen, Nitric Acids, Hydrogen Peroxide, Halogens and Aryidiazonium Salts... 

Among the oxidative procedures for preparing azo compounds are oxidation of aromatic amines with activated manganese dioxide oxidation of fluorinated aromatic amines with sodium hypochlorite oxidation of aromatic amines with peracids in the presence of cupric ions oxidation of hindered aliphatic amines with iodine pentafluoride oxidation of both aromatic and aliphatic hydrazine derivatives with a variety of reagents such as hydrogen peroxide, halogens or hypochlorites, mercuric oxide, A-bromosuccinimide, nitric acid, and oxides of nitrogen. 

Only a few of rather numerous reactions of oxidation of alkoxides by oxygen, peroxides, halogens, and other compounds may be used for synthesis of M(OR) (with considerable yields). These reactions are known for uranium alkoxides [197, 856], such as... 

Recently the amino acid sequence of vanadium chloroperoxidase was determined to have similar stretches with three families of acid phosphatases, which were previously considered unrelated [72], This sequence raises questions about the phosphatase activity of apo-V-ClPO and whether the acid phosphatases can coordinate vanadate and carry out peroxidative halogenation chemistry. In fact, apo-V-C1PO does have phosphatase activity, catalyzing the hydrolysis of/i-nitrophe-nol phosphate (p-NPP). In addition, /i-NPP displaces vanadate from V-CIPO. At this point, the haloperoxidase activity of the acid phosphatases containing coordinated vanadium(V) has not been reported. 

Scheme 6 The catalytic cycle for peroxidative halogenation catalyzed by MeRe03.

Coordination compounds of vanadium(V) also catalyze peroxidative halogenation reactions where the reactive oxidant is a monoperoxo complex of a mononuclear vanadium compound (Figure 6) [11,22,92-95,99]. 

Flammable liquids Ammonium nitrate, chromic acid, hydrogen peroxide, nitric acid, sodium peroxide, halogens... 

In many cases the formation of amalgams, active metals, hydrogen peroxide, halogens, or hydroxyl radicals has been postulated as the electrochemical step which then is followed by a purely chemical reaction. One of the usual arguments for these intermediates is that the reaction follows a route which may be duplicated by the chemical reagent, but this does not prove the presence of these intermediates in the electrolytic reaction. 

Thiols are powerful reducing agents, which may be oxidized by O2, peroxides, halogens, sulfoxides, or metal ions in high oxidation states [FeCb, Pb(02CMe)4] usually disulfanes are formed in these reactions. Oxidation of thiols by sulfur(IV) or sulfur(Vl) compounds often results in mixtures of polysulfanes. 

Few redox studies with cubic mesoporous materials have been reported [52]. The large, complex, three-dimensional pore system offers a unique environment. Ti- and Cr-substituted MCM-48 have been studied for the selective oxidation of methyl methacrylate and styrene to methyl pyruvate and benzaldehyde, respectively, using peroxides as oxidants and were found to outperform TS-1. Ti-MCM-48 has also been found to be better than Ti-MCM-41, TS-1 and Ti02 for the photocatalytic reduction of CO2 and H2O to methane and methanol. Ti-grafted MCM-48 has also been reported as the first functional biomimic of vanadium bromoperoxidase, active at neutral pH and used in the peroxidative halogenation of bulky organic dyes. 

The preparation of sulfinic acids by the oxidation of thiols is difficult because of the danger of overoxidation to the sulfonic acid however, in certain cases various oxidants, e.g. dilute hydrogen peroxide, halogens or m-chloroperbenzoic acid (MCPBA), have been successfully used (Scheme 2). 

Acids, alkaloids, aluminum. Iodine, oxidizers, strong bases Acids, bases, copper, magnesium perchlorate Ammonium nitrate, chromic acid, hydrogen peroxide, nitric acid, sodium peroxide, halogens Alcohols, aldehydes, ammonia, combustible materials, halocarbons, halogens, hydrocarbons, ketones, metals, organic acids... 

Incompatibilities and Reactivities Oxidizers, peroxides, halogens, catalysts for vinyl or ionic polymers aluminum, iron chloride, copper [Note Usually contains an inhibitor such as tert-butyl catechol.]... 

Simple optically active phosphines can be converted back into phosphonium salts without any change of configuration if benzyl or alkyl halides are used (reversal of Equation 13.57). Oxidation to phosphine oxides with hydrogen peroxide or sulphurisation to phosphine sulphides with elemental sulphur also proceeds with retention of configuration. On the other hand, racemisation or complete inversion occurs if oxidation is carried out with diethyl peroxide. Halogenation to a phosphonium compound followed by hydrolysis results in inversion (13.63). 

Moreover, amavadin also catalyses the abovementioned peroxidative oxidation of alkanes, as well as their peroxidative halogenations [65], although with a much lower activity. 

Chemical oxidizers used to disinfect RO systems include hydrogen peroxide (peroxide), halogens, and ozone. Although halogens (and specifically chlorine) are the most popular oxidizers using in conjunction with RO pretreatment, they do not have the highest oxidization-reduction potential (ORP). Table 8.8 lists the ORP for several oxidizers. As the table shows, ozone and peroxide have nearly twice the ORP or oxidative power as chlorine. Despite the relatively low ORP, chlorine is the most commonly used disinfectant in brackish water RO pretreatment due to its ease of use and its ability to provide residual disinfection (for seawater desalination using RO, bromine (as HOBr)... 

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