Oxidative methods

The use of KMnO provides a simple and effeedve method for coaverting various nitre compounds to aldehydes and ketoaes in 80-96% yield, and evea quatetnary aldehydes are prepared despite their instability by this method, as shown in Eq. 6.6.  

I lEF REpCTIOI I iPLOEH iOEE. KETOl lEE. PI ID CpRBO/Tr LlC pCIOE) 161 

When the substrate does not contain a reactive carbon-carbon double bond, the ozonolysis procedure appears to provide a convenient and efficient method for the conversion of primary and secondary nitro compounds into carbonyl compounds fEq. 6.7.  

Anodic oxidation of nitronate anions provides an artracdvemethod for theNef reaction fEq. 

Dimethyldioxirane oxidation of nitronaies anions affords the correspondmg carbonyl products. Highest yields are obtained when one equivalent of water Is added before the oxidation fEq. 6.9).  

Sodium chlorite under phase-transfer catalysis conditions (CH2Cl2-Na0H-Bu4NHS04) is also a good choice for the Nef reaction of primary and secondary nitro compounds (Eq. 6.10).16 

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Well, that should be enough examples to give you a good idea of how this Wacker oxidation method works. There are a lot more interesting variations that bees have been posting on the Hive if you wish to read more. 

For developing osmium catalyzed oxidation methods for preparing chiral com pounds of high optical pu rity Professor K Barry Sharpless (Scripps Research Institute) shared the 2001 Nobel Prize in chemistry... 

To the synthetic chemist the most important of the reactions m Table 17 1 are the last two the oxidation of primary alcohols to aldehydes and secondary alcohols to ketones Indeed when combined with reactions that yield alcohols the oxidation methods are so versatile that it will not be necessary to introduce any new methods for preparing aide hydes and ketones in this chapter A few examples will illustrate this point... 

Oxidation inhibitors Oxidation methods Oxidation reactions Oxidation resistance Oxidations... 

PPQs possess a stepladder stmcture that combines good thermal stabiUty, electrical insulation, and chemical resistance with good processing characteristics (81). These properties allow unique appHcations in the aerospace and electronics industries (82,83). PPQ can be made conductive by the use of an electrochemical oxidation method (84). The conductivities of these films vary from 10 to 10 S/cm depending on the dopant anions, thus finding appHcations in electronics industry. Similarly, some thermally stable PQs with low dielectric constants have been produced for microelectronic appHcations (85). Thin films of PQs have been used in nonlinear optical appHcations (86,87). 

By far the most commonly used oxidation method is the corrected permanganate number test (26) in which the number of mL of 0.1 KMnO consumed by 1 g of oven-dried pulp under specified conditions (kappa number) is deterrnined (TAPPl Historical Method T236 hm-85). Typical kappa numbers for representative pulps are shown in Table 3. 

From Boric Oxide and Alcohol. To avoid removing water, boric oxide, B2O3, can be used in place of boric acid. The water of reaction (eq. 4) is consumed by the oxide (eq. 5). Because boric acid reacts with borates at high temperatures, it is necessary to filter the reaction mixture prior to distillation of the product. Only 50% of the boron can be converted to ester by this method. In cases where this loss can be tolerated, the boric oxide method is convenient. This is particularly tme for methyl borate and ethyl borate preparation because formation of the undesirable azeotrope is avoided. 

Sodium chlorite is used to produce chlorine dioxide by chemical oxidation, electrochemical oxidation methods, or by acidification with acids. Most of the commercial methods employ chlorine or sodium hypochlorite. 

Although 1,2-benzisothiazoles can be prepared by the oxidation method, they are also available by cyclization of o-mercaptobenzaldoximes and ketoximes with polyphosphoric acid (72AHC 14)43, 73JCS(P1)356, 77JCS(P2)1114). This method has been improved by the use of S-t- butyl analogues, which do not suffer from the instability of the free thiols (79SST 5)345). 

Three rapid oxidation methods are typically used to destroy combustible contaminants (1) flares (direct-fiame-combnstion), (2) thermal combustors, and (3) catalytic combustors. The thermal and flare methods are characterized by the presence of a flame during combustion. The combustion process is also commonly referred to as afterburning or incineration. ... 

Chemical oxygen demand (COD) A measure of the amount of oxygen, expressed in milligrams per liter, required to oxidize organie matter present in a substanee using a ehemieal oxidation method. 

The most important routes to B-norsteroids involve oxidative fission of 5,6-double bonds to keto acids or keto aldehydes which are then closed to five-membered rings by condensation reactions. Three of the best oxidation methods are exemplified in the following examples chosen from the cholestane, androstane, and pregnane series. 

Alkoxybenzofuroxans are weU-known, and the hypochlorite oxidation method is usually used for their preparation. For the formation of haloalkoxybenzofuroxans from nitrobenzofuroxans, see Section VII, B. 

Novel aerobic oxidation method using A-hydroxyphthalimide as a catalyst (transformations of hydrocarbons to alcohols and/or carbonyl compounds) 99YGK24. 

The oxidation methods described previously are heterogeneous in nature since they involve chemical reactions between substances located partly in an organic phase and partly in an aqueous phase. Such reactions are usually slow, suffer from mixing problems, and often result in inhomogeneous reaction mixtures. On the other hand, using polar, aprotic solvents to achieve homogeneous solutions increases both cost and procedural difficulties. Recently, a technique that is commonly referred to as phase-transfer catalysis has come into prominence. This technique provides a powerful alternative to the usual methods for conducting these kinds of reactions. 

Methyl-2-hexcne has a disubstituted double bond, RCH=CHR, and would probably give a mixture of two alcohols with either hydration method since Markovnikov s rule does not apply to symmetrically substituted alkenes. 3-MethyI-3-hexene, however, has a trisubstituted double bond, and would give only the desired product on non-Markovnikov hydration using the hydroboration/oxidation method. 

In conclusion, the above summary of oxidation methods shows that there is still room for further improvements in the field of selective olefin epoxidation. The development of active and selective catalysts capable of oxidizing a broad range of olefin substrates with aqueous hydrogen peroxide as terminal oxidant in inexpensive and environmentally benign solvents remains a continuing challenge. 

Measurement of the absorption rate of carbon dioxide in aqueous solutions of sodium hydroxide has been used in some of the more recent work on mass-transfer rate in gas-liquid dispersions (D6, N3, R4, R5, V5, W2, W4, Y3). Although this absorption has a disadvantage because of the high solubility of C02 as compared to 02, it has several advantages over the sulfite-oxidation method. For example, it is relatively insensitive to impurities, and the physical properties of the liquid can be altered by the addition of other liquids without appreciably affecting the chemical kinetics. Yoshida and... 

In 1960, Yoshida et al. (Y4), working with a geometrically similar system and with the sulfite-oxidation method, confirmed the results reported by Cooper et al. They also showed that the gas film does not offer any resistance to the mass transfer of oxygen from air to the sodium sulfite solution. In addition, they found that the mass-transfer coefficient per unit area was equal for water and for aqueous sodium sulfite. 

The oxidation method can also be applied to asymmetrically substituted 1,3-diaryltriazenes. The oxygen attacks the nitrogen atom nearest to an electron-releasing... 

The following subdivision has been adopted in this section oxidation methods reduction methods pyrolysis to SOz addition to activated double bonds spectroscopic methods chromatographic methods. 

A subdivision similar to that for sulphones has been adopted oxidation methods reduction methods methods dependent on basic properties complex formation with inorganic salts spectroscopy chromatography. 

Table 11 affords a survey on oxidation methods of thioethers and sulfoxides. 

Nitric acid is also useful as an oxidant for the formation of sulphate from sulphones. Two such methods have been developed, firstly the established AOAC method which involves oxidation with a mixture of nitric acid and bromine221, and secondly the Carius method222. The latter is probably the oldest method used for the determination of sulphones as sulphate. This oxidation procedure involves heating the sulphone with concentrated nitric acid and sodium chloride at 280-300 °C in a sealed tube. The traditional method as described is prone to explosions. This problem may be alleviated by using less nitric acid whilst employing an oxygen atmosphere2 23,224. The Carius method is slower than the other oxidation methods described above but it usually yields the best results. 

Figure 10.20 Substrate analogs of dihydroxyacetone phosphate accessible by the CPO oxidation method, and spontaneous, reversible formation of arsenate or vanadate analogs of dihydroxyacetone phosphate/n s/tu for enzymatic aldol additions.

It has proved possible to convert CH2 to C=0 groups, even if they are not near any functional groups, indirectly, by the remote oxidation method of Breslow (see... 

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