Molybdenum pentoxide oxidation

The gas-phase equilibrium between 2-hydroxypyridine and 2-pyridone favours the hydroxy-form, but in the equilibrium between 2-hydroxypyridine iV-oxide and N-hydroxy-2-pyridone, the major tautomer is the hydroxy-pyridone. Bicyclic adducts between 2-pyridones and dimethyl acetylene-dicarboxylate, unobtainable at atmospheric pressure, have been obtained at 10—15 kbar. A novel route to iV-hydroxy-2-pyridone involves the trimethyl-silylation of 2-pyridone followed by oxidation of the resulting 2-(trimethyl-silyloxy)pyridine with the DMF complex of molybdenum pentoxide. p-Nitro-phenols (45) and nitro-acetamides (46) are formed from the reaction of 3,5-dinitro-2-pyridones (43) with the sodium salts of /3-keto-esters (44) (Scheme 20). ... 

Formation and subsequent destruction of an enolate anion through oxidation with the molybdenum pentoxide/pyridine/HMPA (MoOPh) reagent to generate acyloins (Equation 9.11). 

Oxidation of methanol to formaldehyde with vanadium pentoxide catalyst was first patented in 1921 (90), followed in 1933 by a patent for an iron oxide—molybdenum oxide catalyst (91), which is stiU the choice in the 1990s. Catalysts are improved by modification with small amounts of other metal oxides (92), support on inert carriers (93), and methods of preparation (94,95) and activation (96). In 1952, the first commercial plant using an iron—molybdenum oxide catalyst was put into operation (97). It is estimated that 70% of the new formaldehyde installed capacity is the metal oxide process (98). 

Aluminium oxide, arsenic trioxide, bismuth trioxide, calcium oxide, chromic oxide, lanthanum oxide, lead dioxide, magnesium oxide, manganese dioxide, molybdenum trioxide, phosphorus pentoxide, stannic oxide, sulfur dioxide (explodes), tantalum pentoxide, tungsten trioxide, vanadium pentoxide. 

Lithium is used to reduce metallic oxides in metallurgical operations, and the reactions, after initiation at moderate temperatures, are violently exothermic and rapid. Chromium(III) oxide reacts at 185°C, reaching 965° similarly molybdenum trioxide (180 to 1400°), niobium pentoxide (320 to 490°), titanium dioxide (200-400 to 1400°), tungsten trioxide (200 to 1030°), vanadium pentoxide (394 to 768°) also iron(II) sulfide (260 to 945°), and manganese tclluridc (230 to 600°C)... 

Phthalic anhydride is prepared by oxidizing o-xylene. The oxidation may be performed either in the gas phase with vanadium pentoxide as a catalyst or in the liquid phase with dissolved manganese, molybdenum, or cobalt salts as catalysts ... 

Metal Oxides. Reduction of metal oxides such as chromium(III) oxide, molybdenum trioxide, niobium pentoxide, tungsten trioxide, and vanadium pentoxide is violently exothermic and rapid.9... 

Wenda, E. 1985. Phase diagram of vanadium pentoxide-molybdenum trioxide-silver oxide. I. Phase diagram of vanadium pentoxide-silver oxide system. J. Therm. Anal. 30 879-887. 

This review deals only with the heterogeneous oxidation of-carbon monoxide by solid materials which show some catalytic activity or a fast surface reaction. It does not include purely stoichiometric reagents used in detection and analysis, such as iodine pentoxide, mercuric oxide, palladium salts activated by molybdenum salts, or liquid-gas systems. A review of such agents has recently been presented elsewhere (11). Furthermore, no attempt has been made to provide complete coverage of the numerous patents in this field, although a number of the more important ones are mentioned. 

Despite this they should be considered as possible alternatives in cases where more familiar methods fail. Amongst this group of activators are p-toluenesulfonyl chloride, tiifluoromethanesulfonic anhy-dride,silver tetrafluoroborate, molybdenum oxide, phosphorous pentoxide, trichloromethyl chloroformate, 2-fluoro-l-methylpyridiniumsulfonate, chlorosulfonyl isocyanate, antimony penta-chloride (for which an X-ray structure of the DMSO-SbCb conqilex was obtained) and phenyl dichlo-rophosphate. ... 

Tungsten trioxide, like molybdenum trioxide, possesses in marked degree the property of combining with other acidic oxides, such as phosphorus pentoxide, arsenic pentoxide, silica, and boron trioxide, in varying proportions, producing heteropolyacids which contain the VOL, VII. III. 193 13... 

---