Depolymerization products, hydrogen distribution

The concept of a (bound) formaldehyde intermediate in CO hydrogenation is supported by the work of Feder and Rathke (36) and Fahey (43). Experiments under H2/CO pressure at 182-220°C showed that paraformaldehyde and trioxane (which depolymerize to formaldehyde at reaction temperatures) are converted by the cobalt catalyst to the same products as those formed from H2/CO alone. The rate of product formation is faster than in comparable H2/CO-only experiments, and product distributions are different, apparently because secondary reactions are now less competitive. However, Rathke and Feder note that the formate/alcohol ratio is similar to that found in H2/CO-only reactions (36). Roth and Orchin have reported that monomeric formaldehyde reacts with HCo(CO)4 under 1 atm of CO at 0°C to form glycolaldehyde, an ethylene glycol precursor (75). The postulated steps in this process are shown in (19)—(21), in which complexes not observed but... 

There are very few examples of direct hydroxylation of olefins using hydrogen peroxide, since these methods are limited to polymer applications or derivatization of natural products. Vinyl monomers have been hydroxy-lated in an alcoholic medium using acidic hydrogen peroxide 111 normally the acid is methanesulfonic. Natural rubber has also been hydroxylated, and simultaneously depolymerized by employing a hydrogen peroxide/UV system.112 The product distribution can be altered by varying the irradiation time. 

Considering the data described above, it appears that vv ith an iron catalyst the depolymerization of an alkyl group, either directly to form a lower carbon alkyl group and methylene (CH2) or indirectly by the addition of hydrogen in a hydrocracking mechanism, does not occur to an extent that it makes a significant contribution to the product distribution. It does appear that hydrocracking may make a contribution to the product distribution when cobalt is used as the catalyst but that additional data are needed to verify that this is the case. 

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