Methane hydrogen abstraction from

The hydrogen abstraction from alkoxyamidyl 102 has been modeled at B3LYP/ 6-31G level by the reaction of methyl radical (R = CH3 ), with methoxy-formamidyl 102e giving 103e and methane. Energies are presented in Table 13. 

Hydrogen abstraction from methane by Cl and H occurs via the following bimolecular metathesis reactions ... 

In the presence of an amine, the principal method of forming methane is again by hydrogen abstraction from the amine. 

The above analysis indicates clearly that contrary to views expressed by many workers on methane oxidation, the termolecular reaction of CH3 + 02 must be of major importance at these temperatures. Benson (10) has expressed the view that the bimolecular reaction is unimportant even at high temperature and has suggested that the CH302 radical forms CH3O2H by hydrogen abstraction from H02, H202, or possibly H2. Preliminary analysis suggests that even if this were the case, a second-order... 

De Vries (79) reported that solutions of Ti(CH3)Cl3 can be photodecom-posed, but obtained no evidence for production of methyl radicals. Deuterium labeling studies indicated that the hydrogen incorporated into the methane produced originated from the methyl ligands. No hydrogen abstraction from the solvent was detected and no further details were presented. 

The flash photolysis of hexaarylbiimidazole produces imidazolyl radicals " which have been shown to be more nearly planar than the parent dimers ort/io-substituents in the aryl rings decrease the radical stability. The radicals oxidize electron-rich substrates by rapid electron abstraction from tertiary amines, iodide, and metal ions, and by hydrogen abstraction from phenols, mercaptans, secondary amines, and active methylene com-pounds." " Studies have been made of the photooxidation of /euco-triphenyl-methane dyes by these radicals." " ... 

There is agreement among the researchers that the first and most fundamental part of the methane activation reaction is hydrogen abstraction from the CH molecule to form methyl radicals consequently, it is appropriate to start this overview with a section devoted to the formation and reaction of these species. The most comprehensive studies on this subject have been conducted by the group of Lunsford and coworkers whose objective was to establish a relation between methane conversion, surface-assisted generation of methyl radicals (CHj ), and the formation of C2 hydrocarbons. Direct measurement of the methyl radical production was... 

The chromone (52) undergoes photochemical addition of ethene. The primary product from this cycloaddition, presumed to be (53), is photo-chemically reactive and is converted into (54) and (55). The former of these is a key intermediate in a synthetic strategy to tricothecene analogues. Both (54) and (55) arise via the Norrish Type II reactivity of (53). Thus hydrogen abstraction from the methoxy substituent by the excited carbonyl group results in a 1,4-biradical that either ring closes to (54) or fragments with the loss of methanal to yield the enol of (55). 

Recent theoretical calculation of hydrogen abstraction from methane by the formaldehyde triplet has shown that a = 9.2° and 3 = 108.9° in the transition state. The formaldehyde triplet is nonplanar the degree of pyramidalization is 34.8°. D. Severance, B. Pandey, and H. Morrison, J. Am. 

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