| Abstract: | Mass spectra of certain selenobases and selenonucleosides, and some of their trimethylsilyl and O,N-permethyl derivatives have been studied from the standpoint of structural characterization, and in order to ascertain the influence of selenium on normal fragmentation patterns. Molecular ion abundances of the selenouracils are intermediate between those of the corresponding oxygen and sulfur analogs. Fragmentation processes are similar to those of the corresponding normal bases and nucleosides but with additional ions resulting from expulsion of Se or SeH in most cases. Trimethylsilylation occurs at approximately the same rate as for normal bases and nucleosides but the products show decreasing stability with prolonged heating. A least squares procedure is demonstrated which generates monoisotopic mass patterns and assists in interpretation of the mass spectra. |
