Abstract
Electron ionization mass spectra of 3-propyl-3-methylisocoumarin (1 and 2), 3-methyl-3, 4-dihydroisocoumarin (5) and related compounds (3 and 4) are discussed. The mass fragmentation patterns are assigned with the help of LREIMS and HREIMS peak mat ching of molecular ion peaks obtained by EIMS are also given.