Ab initio insights into amide bond cleavage reactions of formamide with substituted methyl cations XCH2+ (X = OH, F, and Cl)

The gas phase reactions of the substituted methyl cations, XCH2+ (X = F, HO , and Cl), with formamide were investigated using ab initio calculations, A ddition of the carbocations at the nitrogen atom of the amide bond yields " N adducts" that are less stable than the "O adducts" arising from attack at the carbonyl oxygen atoms. The subsequent fragmentation reactions of these adducts were examined including: (1) fragmentation of the "O adduct" by el imination of HX via a transition structure involving 1, 6 H+ transfer, resu lting in the formation of HC(OCH2)NH+; (2) fragmentation of the "N adduct" by elimination of HX via a transition structure involving 1, 3 H+ transfer resulting in the formation of HC(O)NHCH2+ (3) fragmentation of he "N adduct " via a transition structure involving 1, 3 HC(O)1 transfer resulting in th e formation of HC(O)XCH2NH2+, which decomposes to yield HC(O)X and CH2NH2(when X = OH and Cl); (4) fragmentation of the "N adduct" via extrusion of CO (when X = F and Cl). (C) 2000 Elsevier Science B.V.