Crystal structures and mass spectral fragmentation studies of some new carbacylamidophosphate compounds

Abstract

Twenty new carbacylamidophosphates R′ 2P(O)NHC(O)R, where R = acetyl and benzoyl derivatives, R′ = 3, 5, 6 and 7 membered ring amines, were synthesized and characterized by IR, 1H, 13C and 31P NMR spectroscopy, and elemental analysis. The crystal structures of CCl 3C(O)NHP(O)[N(C 5H 10)] 2 ( 1d), CHCl 2C(O)NHP(O)[N(C 5H 10)] 2 ( 2d), Cl–C 6H 4C(O)NHP(O)[NH(C 5H 9)] 2 ( 5b) and Cl–C 6H 4C(O)NHP(O)[N(C 4H 8)O] 2 ( 5e) have been determined. All four compounds indicate the formation of intermolecular –P O…H–N– hydrogen bonds which give dimeric aggregates. They were centrosymmetric in 5b and 5e. Also, the mass spectra of these compounds, in addition to our previously synthesized 29 carbacylamidophosphates, were recorded and the observed fragmentation behaviors were studied. The main pathways of fragmentation of N-acetyl and N-benzoyl phosphoric amide derivatives indicated that the molecular ions involve mainly a radical cationic center at the carboxyl oxygen. All the N-benzoyl and N-acetyl phosphoramidates rearranged to the O-phosphorylated benz- or acetamides, and those readily lost the (R′) 2PO 2 radicals and yielded N-protonated nitrilium ions R–C NH + and ▪. The greater intensities for the ▪ ions in the N-benzoyl derivatives relative to R–C NH + for the N-acetyl derivatives may due to differences in the P O, C O, P–N amide and C–N amide bond lengths and their different specific properties in the parent molecules.