A tandem mass spectrometry study of [C 6,H 5,O] + ions

Abstract

Tandem mass spectrometric methods and appearance energy measurements have been used to identify and characterize four isomeric [C 6,H 5,O] + ions. The phenoxy cation, C 6H 5O +, has a ΔH f o = 207 kcal mol −1, while the meta- and para-HOC 6H + 4 ions have ΔH f o values at ca. 220 kcal mol −1; the ortho isomer is higher in energy by 5–10 kcal mol −1. Much lower in energy is the conjugated cyclopentadienylcarbonyl ion, estimated ΔH f o ≈ 161 kcal mol −1. The meta- and para-HOC 6H + 4 ions could not be distinguished by mass spectrometric methods, but the ortho isomer differs in its metastable ion characteristics, having a significantly different kinetic energy release for CO loss. Collisional activation mass spectrometry allowed distinction between the ions: phenoxy, hydroxyphenyl and C 5H 5CO +. Greater differences between the isomers were observed in their neutralization-reionization mass spectra.