EI/MS/MS spectra of N-monosubstituted cyanoacetamides

Abstract

The electron-ionization induced mass spectra of twenty six N-monosubstituted cyanoacetamides were recorded and their fragmentation patterns were studied. The effect of N-alkyl and N-aryl substituents to the fragmentation of the investigated compounds was discussed. Mechanistic generalization lead to a conclusion that fission of the carbon-carbon bonds next to carbonyl function or nitrogen were processes common for N-alkyl and N-(4-substituted phenyl) cyanoacetamides. In some amides, the elimination of the acyl group by a ketene fragment gave rise to the more stable ion. Cycloalkyl amides could not fragment by single carbon-carbon bond fission, but subsequent rearrangement resulted in formation of stable even electron ion. N-(4-substituted phenyl) cyanoacetamides were more stable showing also characteristic fragmentation depending on substituent present at phenyl ring.

U ovom radu su proučavani fragmentacioni putevi dvadeset šest N-monosupstituisanih cijanoacetamida dobijenih jonizacijom izazvanom bombardovanjem elektronima. Na osnovu definisanih fragmentacionih puteva diskutovan je uticaj prisutnih N-alkil i N-aril supstituenata. Sagledavanjem mehanizama fragmentacija ispitivanih N-monosupstituisanih cijanoacetamida uočava se da je cepanje veze ugljenik-ugljenik susedne karbonilnoj grupi ili azotu proces uočen i kod N-alkil i N-(4-supstituisanih fenil) cijanoacetamida. Kod nekih amida, eliminacija acil grupe u vidu fragmenta ketena dovodi do nastajanju stabilnijih jona. Cikloalkil amidi ne mogu da se fragmentišu samo cepanjem veze ugljenik-ugljenik, već u narednom koraku pregradnje daju stabilnije parne jone. N-(4-supstituisani fenil) cijanoacetamidi se stabilni u primenjenim jonizacionim uslovima i pokazuju karakteristične fragmentcije na koje utiče prisutni supstituent na fenilnom jezgru.