Ammonia hydrogen abstraction from

Confirmation and extension of this mechanism was obtained by Adams and Jennings 97,109) using propylene labeled with deuterium in various positions. Ammonia was also added to the feed to produce acrylonitrile. After reasonable corrections for small effects of propylene isomerization and deuterium exchange, the results were in quantitative agreement with a model in which allylic hydrogen abstraction occurs to form an allylic intermediate followed by hydrogen abstraction from either end. The model is illustrated by the following scheme for l-propene-3d. 

The ammoxidation reaction mechanism for xylenes is similar to that for toluene. The xylene substrate is activated by hydrogen abstraction from the methyl groups with subsequent reaction with activated ammonia converting the methyl group to an amine, then to an imine, and finally to a nitrile. In the case of xylene ammoxidation, the ammoxidation of the methyl groups to cyano functionalities occurs sequentially rather than concurrently (73,76). 

The rate of combination of trifluoromethyl radicals to form hexafluoro-ethane has been measured by the flash photolysis of trifluoromethyl iodide coupled with rapid-scan i.r. spectroscopy in the absence of an inert diluent (At, N2, or COt) carbon tetrafluoride and tetrafluoroethylene were also formed, presumably via fluorine atom abstraction from trifluoroiodomethane by hot trifluoromethyl radicals (c/. ref. 27). Photolysis of trifluoroiodomethane has been used in studies on (i) the direction of radical attack on 1,3,3,3-tetrafluoropropene [- CFj CHI CHFCF, (75%) + (CFa)jCH CHFl (25%)] (ii) the rates of hydrogen abstraction from ammonia, ammonia-ethylene oxide, silane, trimethylsilane, tetramethylsilane, and cycloalkanes and (iiQ the competitive addition of the CFj- radical to ethylene and vinylidene fluoride. Radicals formed by photolysis of the fluoroalkyl iodides CFJ, C FJ, n-C,F,I, (CF,)jCFI, (CFaljCHI, (CFalaCDI, (CFa)jCClI, and (CFa)iCPhI (the last was synthesized by treatment of CFs CPh CTj with CsF and iodine in DMF) have been... 

Steacie, E. W. R., and A. F. Trotman-Dickenson The Reactions of Methyl Radicals. IV. The Abstractions of Hydrogen Atoms from Cyclic Hydrocarbons, Butynes, Amines, Alcohols, Ethers and Ammonia. J. chem. Physics 19, 329 (1951)-... 

Abstraction of a hydrogen atom from the solvent HS [Eq. (66)] makes it desirable to run the reaction in a solvent that is a poor hydrogen-atom donor liquid ammonia is a preferred solvent. Inorganic salts, such as potassium iodide or bromide, may be employed as supporting electrolyte in the SRN1 reaction in NH3. 

In conclusion, the major role in these examples is played by the basic oxygen ions, which can display nucleophilic reactivity and abstract hydrogen ions from methanol, phenol, and even ammonia to form reactive negatively charged intermediates (264). 

The formation of acrolein from free allyl radical and MOO3 can be explained by the formation of a rr-ally 1 surface complex which forms a cr-O-allyl species followed by hydrogen abstraction (Scheme 6) (20). When ammonia is present, the formation of surface NH species followed by the analogous... 

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