Shmuel Zitrin

Stereochemistry of retro-diel-salder fragmentation in gas-phase ions formed by chemical ionization

Abstract Retro Diels Alder fragmentation is highly stereospecific in the diones 1 under chemical ionization conditions, both with methane and isobutane as the reagent gases. Only the cis -isomers yield abundant protonated diene and quinone ions. The isotope effect indicates preferential protonation on a CO oxygen, and a subsequent H-migration prior to the formation of the protonated diene cations in the cis isomers.

Identification of Opium by Chemical Ionization Mass Spectrometry

Abstract The five major alkaloids of opium - morphine, narcotine, codeine, thebaine and papaverine - have been identified by the chemical ionization (CI) mass spectrum of opium, without any prior separation. CI reagents used were isobutane, at a pressure of 0.2–0.5 Torr and water at a pressure of 0.05 – 0.07 Torr. Source temperatures were in the range of 155–200°C and probe temperatures in the range of 90–160°C. The base peak in the CI spectrum of opium is at m/e 220, resulting from an unusual cleavage of the MH ion of narcotine.