Oxidation of oxygenated compounds

A brief introduction to the oxidation of oxygenated compounds is appropriate as they are important intermediates in the total oxidation of an alkane through to CO2 + H2O. In the temperature region below 1000 K, the major oxygenated species are aldehydes (ketones from highly branched alkanes) and O-heterocyclic compounds formed via RO2 QOOH iso-merizations. An impression of the relative activity of oxiranes and oxetanes... 

B. Isotopic Studies of Oxidation of Oxygenated Compounds over... 

VI,14. OXIDATION OF UNSATURATED COMPOUNDS WITH OZONISED OXYGEN (OZONOLYSIS)... 

The ff-oxidation of carbonyl compounds may be performed by addition of molecular oxygen to enolate anions and subsequent reduction of the hydroperoxy group, e.g. with triethyl phosphite (E.J. Bailey, 1962 J.N. Gardner, 1968 A,B). If the initially formed a-hydroperoxide possesses another enolizable a-proton, dehydration to the 1,2-dione occurs spontaneously, and further oxidation to complex product mitctures is usually observed. 

HCIO4, one of the strongest of the mineral acids. The perchlorates are more stable than the other chlorine oxyanions, ie, chlorates, CIO chlorites, CIO or hypochlorites, OCf (3) (see Chlorine oxygen acids and salts). Essentially, all of the commercial perchlorate compounds are prepared either direcdy or indirectly by electrochemical oxidation of chlorine compounds (4—8) (see Alkali and chlorine products Electrochemical processing). 

Essential Oils. Volatile oils from plants are referred to as essential oils. The oils can be obtained through steam distillation, solvent extraction, or separation of the oils from pressed fmit. They consist of oxygenated compounds, terpenes, and sesquiterpenes. The primary flavor components of essential oils are oxygenated compounds. Terpenes contain some flavors but are often removed from the essential oil because they are easily oxidized (causiag off-flavors or odors) and are iasoluble. Essential oils are prepared from fmits, herbs, roots, and spices. 

Catalytic combustion is a process in which a combustible compound and oxygen react on the surface of a catalyst, leading to complete oxidation of the compound. This process takes place without a flame and at much lower temperatures than those associated with conventional flame combustion. Due partly to the lower operating temperature, catalytic combustion produces lower emissions of nitrogen oxides (NOx) than conventional combustion. Catalytic combustion is now widely used to remove pollutants from... 

The oxidation of n-butane represents a good example illustrating the effect of a catalyst on the selectivity for a certain product. The noncatalytic oxidation of n-butane is nonselective and produces a mixture of oxygenated compounds including formaldehyde, acetic acid, acetone, and alcohols. Typical weight % yields when n-butane is oxidized in the vapor phase at a temperature range of 360-450°C and approximately 7 atmospheres are formaldehyde 33%, acetaldehyde 31%, methanol 20%, acetone 4%, and mixed solvents 12%. 

Beden, B. Electrocatalytic Oxidation of Oxygenated Aliphatic Organic Compounds at Noble Metal Electrodes 22... 

Hazards arising from the oxidation of organic compounds are greater when the reactants are volatile, or present as a dust or an aerosol. Liquid oxygen and various concentrated acids, e.g. nitric, sulphuric or perchloric acid, and chromic acid are strong oxidizing agents. The use of perchloric acid or perchlorates has resulted in numerous explosions their use should be avoided when possible (refer to Table 6.5). 

Beden, C. Lamy, and J.-M. Leger, Electrocatalytic Oxidation of Oxygenated Aliphatic Organic Compounds at Noble Metal Electrodes, in Modem Aspects of Electrochemistry, Vol. 22, Ed. by J. O M. Bockris, B. E. Conway, and R. E. White, Plenum Press, New York, 1992, pp. 97-264. 

Lenoir, D. (2006) Selective Oxidation of Organic Compounds - Sustainable Catalytic Reactions with Oxygen and without Transition Metals Angewandte Chemie International Edition, 45, 3206-3210. 

Beden B, Lamy C, Leger JM. 1992. Electrocatalytic oxidation of oxygenated aliphatic organic compounds at noble metal electrodes. In Bockris JO M, Conway BE, White RE, eds. Modem Aspects of Electrochemistry. Volume 22. New York Plenum Press, p 97-264. 

Listed in the Table 6.1 are some of the more common sources of oxygen employed for oxidations of organic compounds. Dioxygen is not listed because it requires a catalyst for oxidation at low temperatures. Likewise, hydrogen peroxide and ozone exhibit different activities when used with the proper heterogeneous catalyst. 

The fused indolopyrrolizidine 137 can be transformed into the tetrahydropyrrolizinoquinolone 138 upon reaction with Bu OK while oxygen is bubbled into the solution. (This is an apparently general strategy for the oxidation of indoles.) Compound 138 may then be oxidized with w-chloroperbenzoic acid (MCPBA) to give the dihydropyrido-pyrrolizine 139 <1997TL2997> (Scheme 37). 

Similar mechanisms are suggested for the chemiluminescence of 9-formylacridine 92, 9-formyl- 10-methylacridinium methosulfate 95 9-benzoylacridine 93 and 9(4-nitrobenzoyl)-acridine 94 142> which occurs on oxidation of these compounds with base and oxygen in DMSO. 

Laccase is one of the main oxidizing enzymes responsible for polyphenol degradation. It is a copper-containing polyphenoloxidase (p-diphenoloxidase, EC 1.10.3.2) that catalyzes the oxidation of several compounds such as polyphenols, methoxy-substituted phenols, diamines, and other compounds, but that does not oxidize tyrosine (Thurston, 1994). In a classical laccase reaction, a phenol undergoes a one-electron oxidation to form a free radical. In this typical reaction the active oxygen species can be transformed in a second oxidation step into a quinone that, as the free radical product, can undergo polymerization. 

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