Oxygenation alkanes

Shul pin, G.B., Shilov, A. and Siiss-Fink, G. (2001) Alkane oxygenation catalysed by gold complexes. Tetrahedron Letters,... 

Epoxidation Catalyzed by Metalloporphyrins. Metalloporphyrins, which have thoroughly studied as catalysts in alkane oxygenations, have also been tested as epoxidation catalysts.119,122,244,245,307 Iodosylbenzene (PhIO), sodium hypochlorite, alkyl hydroperoxides, potassium hydrogen persulfate, and molecular oxygen are the oxygen sources used most frequently in these oxidations.119... 

Scheme 10.11 Mixed catalytic cycle for hydroperoxide formation in alkane oxygenation and alkene epoxidation with HOOH and cw-VO(bpy)2Y, via a homolytic and heterolytic cleavage of peroxo intermediates, respectively (after Knops-Gerrits et alPTi).

Reacts to form explosive products with alkanes + oxygen (forms peroxides), cyano-guanidine, perchloric acid (forms fluorine perchlorate gas), potassium chlorate (forms fluorine perchlorate gas), potassium hydroxide (forms potassium trioxide). 

Radical cations are probably involved in the photooxidation of olefins [1-7, 24, 50-54, 56, 61, 66] (Eqs. 2 and 5). Many oxidizable arenes and dienes are, similarly, oxidatively cleaved or rearranged by routes consistent with initial formation of a radical cation. As we saw above, the observed oxidative cleavage product probably derives from the combination of a surface-bound radical cation with superoxide or adsorbed oxygen. With alkanes or simply substituted alkenes, however, the capture of a photogenerated hole is often thermodynamically forbidden. Thus, instead of radical cations, radicals formed by hydrogen atom abstraction by an activated oxygen species dominate the observed chemistry. With alkanes, oxygenation at sites... 

Catalysts were tested in a fixed bed quartz tubular reactor, at atmospheric pressure, in the temperature interval 500-600 C [2]. The catalyst (particle size 0.42-0.59 mm) were mixed with SiC of the same size at a catalyst/SiC volume ratio of 1/4. The feed consisted of a mixture of alkane/oxygen/helium in a molar ratio of 4/8/78 (ethane, propane) and 5/20/75 (n-butane). In order to achieve a similar alkane conversion, samples of 0.7-1.7 g and total flow of 100-200 ml min were used to modify the contact time (W/F). 

FcPc-VPI-5 [8, 18] is an active catalyst in the alkane oxygenation with tBuOOH at room temperature. For cyclododecane and cyclohexane as substrate, TON of 125 and 313 have been obtained, respectively, assuming that all FePc are accessible. When the real situation is taken into account that FePc arc present in the monodimensional pores as stacks of Pc with only the pore mouths being accessible, real TON should be in the range of a few hundred thousand, corresponding to a TOF of a few hundred turnovers per minute, a value that largely surpasses all literature values on related systems. These piles of buried FePc... 

In recent years, numerous systems for alkane oxygenation based on molecular oxygen, a reductant and a metal catalyst have been described. Some of these systems will be considered in the present section. 

The alkane/oxygen ratio (Figures 1 and 2) was the most important variable for o ration of the single-gauze reactor. Temperatures, reactant conversions, and product selectivities all changed significantly as Cg/Oj was varied from 0.5 to 5.0. From cyclohexane, oxygenates were produced at >40% selectivity for 2. Nearly 70% selectivity to thrw particular... 

The simplest kinetic scheme of the alkane oxygenation based on the kinetic data was proposed. In the first stage, ferrocene FeCp2 is oxidized to ferricenium cation (FeCp2)" ", which is in turn transformed into species Fe that is a fragment containing one iron ion. 

Scheme 15.1 Reaction pathways for the ODH of alkanes. Oxygenated products are not considered...

---