Stereochemical differentiation of isomeric trinorbornane-2,3- and trinorbornane-2,5-diols by chemical ionization mass spectrometry

Abstract

Because stereoisomeric trinorbornane-2,3- and trinorbornane-2,5-diols cannot be distinguished under electron ionization, their differentiation was investigated under chemical ionization. The spectra were recorded using ammonia, isobutane, methane, acetone and trimethyl borate as reagent gas. Although all the stereoisomers could be identified, the differences between the cis-2,3-diols were minor. By contrast, the trans-2,3- and 2-endo-5-endo-diol isomers were easily differentiated from their corresponding stereoisomers. Stereochemical effects were greatest under isobutane, acetone and trimethyl borate chemical ionization. The collision-induced dissociation mass spectra of the [M + NH₄]⁺ adduct ions also allowed most of the stereoisomers to be distinguished.