Oxygen olefination

Mann and Ko [202] likewise examined the selective oxidation of isobutene on bismuth molybdate. With an integral flow reactor, the highest selectivity was obtained at over 30% conversions for an oxygen/olefin ratio of 2/1 and a W/F = 2.5 g h mol-1 (390°C). The data were correlated with a rather complicated Langmuir—Hinshelwood expression inconsistent with a redox mechanism. This was based on a rate-controlling step between adsorbed isobutene and adsorbed oxygen, and included an inhibiting effect of methacrolein by competitive adsorption with isobutene, viz. 

Although these substrates are both inert to singlet oxygen, olefin oxidative cleavage was observed with superoxide. Furthermore, an oxidative equilibration of the olefin radical cations... 

The leveling off of the condensation nuclei concentration after the first few minutes of the irradiation indicates that the size distribution is shifting to larger particles as oxygenated olefin is incorporated into the aerocolloidal mass. 

Anodically initiated [2 + 2 + 3] cycloaddition reaction implying molecular oxygen olefins and 1,3-diketone were also described [273] as yielding a peroxide found to be extremely stable. 

Boyce, C.B.C., Webb, S.B., and Phillips, L., The phosphorus trichloride-oxygen-olefin reaction. Scope and mechanism, J. Chem. Soc., Perkin Trans. 1, 1650, 1974. 

Another possible solution of the problem is to perform the reaction at a very low initial oxygen concentration. Although in the case of alkane partial oxidation this is not favorable for obtaining high yields of target products (oxygenates, olefins, synthesis gas), an almost uniform temperature field can be achieved. 

Sedran et al. revised the corrected model of Chang and found that it was able to predict effectively the product distribution (oxygenates, olefins, and aromatics/paraffins lumps) at various conversion levels and temperatures. 

As indicated below, C=C absorptions vary considerably in intensity, depending upon the symmetry of the bond and on factors such as conjugation, etc. No detailed studies of absolute intensities have been made, but Jones and Sandorfy [86] have compiled a useful summary of intensity data in the A.P.I. series, and Davison and Bates [74] report extinction coefficients for a variety of oxygenated olefines. 

The singlet oxygen + olefin route is particularly effective when the double bond has electron releasing substituents. 

---