title: Electrospray ionization (ESI) fragmentations and dimethyldioxirane reactivities of three diverse lactams having full, half, and zero resonance energies.
abstract: Three lactams having, respectively, ~20, ~10, and 0 kcal/mol of resonance energy have been subjected to electrospray ionization mass spectrometry (ESI/MS) as well as to attempted reaction with dimethyldioxirane (DMDO). The ESI/MS for all three lactams are consistent with fragmentation from the N-protonated, rather than the O-protonated tautomer. Each exhibits a unique fragmentation pathway. DFT calculations are employed to provide insights concerning these pathways. N-Ethyl-2-pyrrolidinone and 1-azabicyclo[3.3.1]nonan-2-one, the full- and half-resonance lactams, are unreactive with DMDO. The "Kirby lactam" (3,5,7-trimethyl-1-azaadamantan-2-one) has zero resonance energy and reacts rapidly with DMDO to generate a mixture of reaction products. The structure assigned to one of these is the 2,2-dihydroxy-N-oxide, thought to be stabilized by intramolecular hydrogen bonding and buttressing by the methyl substituents. A reasonable pathway to this derivative might involve formation of an extremely labile N-oxide, in a purely formal sense, an example of the hitherto-unknown amide N-oxides, followed by hydration with traces of moisture.
authors: Department of Chemistry, Xavier University of Louisiana , New Orleans, Louisiana 70125, United States.
authors: Kathleen M
authors: KM
authors: Morgan
authors: David J
authors: DJ
authors: Ashline
authors: Jessica P
authors: JP
authors: Morgan
authors: Arthur
authors: A
authors: Greenberg
mesh_terms: D004852:Epoxy Compounds / Q000737:chemistry*; D007769:Lactams / Q000737:chemistry*; D015394:Molecular Structure; D011789:Quantum Theory; D021241:Spectrometry, Mass, Electrospray Ionization; D013816:Thermodynamics
chemical_list: D004852:Epoxy Compounds; D007769:Lactams; C064455:dimethyldioxirane