CHARACTERIZATION OF RING CONTRACTION AND ALPHA-CLEAVAGE PRODUCTS OF 3-ALKYL-3,4-DIHYDROISOCOUMARINS AND 3-ARYL-3,4-DIHYDROISOCOUMARINS UNDER ELECTRON IONIZATION MASS-SPECTROMETRIC STUDIES

Electron ionization mass spectra of 3-alkyl-3,4-dihydro-isocoumarins ( 1a-c), 3-(3'-methoxyphenyl- 3,4dihydroisocoumarin (2) , 3-(4'-chloroph enyl)-3,4-dihydroisocoumarins (3) and 3-phenyl-3,4-dihydroisocoumarins (4) are discussed. The major mass fragments are formed by ring contra ctions and alpha-cleavage followed by the elimination of neutral fragm ents and radicals. The mass fragmentation patterns are designed with t he help of EIMS and HREIMS peak matching of molecular ion peaks exhibi ted by EIMS.