Formyl radical, structure

In a potentially significant development in CO reduction chemistry, Rathke and Feder (88h) have found that HCo(CO)4 serves as a catalyst for conversion of CO/H2 mixtures to MeOH and HCOOMe under forcing conditions (300 atm, 200°C), albeit at very slow rates. An activation energy of 40.7 kcal/mol was obtained, and a scheme based on formyl radical chemistry was proposed. While the latter seems premature, the fact that reduction products were observed in the absence of cluster compounds brings into question the necessity of such a structural arrangement. 

The hyperfine coupling for the methyl protons (.<4i,o = 5T G) is markedly less than the proton hyperfine coupling observed for the formyl radical ( iBo= 130 G) and could arise from the normal hyperfine interactions observed in alkyl radicals in which the unpaired electron is located in a carbon 2p-orbital. However, the very large splitting in the formyl radical is attributed to a contribution of the excited state, H- C=0 (Adrian et al., 1962) to the electronic structure and it is feasible... 

Figure 13. Formation and collapse of the tetrahedral oxy-radical intermediate. Optimized structures for A) transition state of the thiyl radical addition to pyruvate (TSl), B) tetrahedral oxy-radical intermediate, and C) transition state of the dissociation of formyl radical (TS2). The energies of these species are 12.3 kcal/mol, 9.9 kcal/mol, and 12.7 kcal/mol, respectively, relative the energy of (methylthiyl + pyruvic acid).

Photolytic. Based on data for structurally similar compounds, acenaphthylene may undergo photolysis to yield quinones (U.S. EPA, 1985). In a toluene solution, irradiation of acenaphthylene at various temperatures and concentrations all resulted in the formation of dimers. In water, ozonation products included 1,8-naphthalene dialdehyde, 1,8-naphthalene anhydride, 1,2-epoxyacenaphthylene, and 1-naphthoic acid. In methanol, ozonation products included 1,8-naphthalene dialdehyde, 1,8-naphthalene anhydride, methyl 8-formyl-1-naphthoate, and dimethoxyacetal 1,8-naphthalene dialdehyde (Chen et al., 1979). Acenaphthylene reacts with photochemically produced OH radicals and ozone in the atmosphere. The rate constants and corresponding half-life for the vapor-phase reaction of acenaphthylene with OH radicals (500,000/cm ) at 25 °C are 8.44 x lO " cmVmolecule-sec and 5 h, respectively. The rate constants and corresponding half-life for the vapor-phase reaction of acenaphthylene with ozone at 25 °C are... 

The formation of a cyclohexyloxyl radical via 6-exo-trig manner is promoted by the rigid bicyclic structure derived from the sugar benzylidene group (eq. 3.57a). Moreover, eq. 3.57b indicates that radical ring closure to a formyl group is preferable to that onto an olefinic group. 

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