NEGATIVE-ION CHEMICAL IONIZATION MASS-SPECTROMETRY IN THE DETERMINATION OF COMPONENTS IN ESSENTIAL OILS

The OH- ion generated from a mixture of N2O and CH4 in a CI source abstracts a proton from oxygenated terpenes. With some exceptions, the [M - H]- ion is sufficiently stable and observed with a high relative abundance. Nucleophilic displacement by the OH- ion produces carboxylate ions from terpene esters, giving information about the acid part of the ester. The relative amounts of loss of water from the [M -H]- ions of carveol stereoisomers are rationalized in view of their stereochemical configurations. The spectra of unsaturated terpene hydrocarbons are complicated by ion-molecule reactions of their [M - H]- ions with N2O. © 1979, American Chemical Society. All rights reserved.