Ammonia chemical ionization mass spectrometry of alcohols: Structural, stereochemical, molecular‐size and temperature effects

Abstract

Abstract Ammonia chemical ionization (CI) mass spectra of various open‐chain, cyclic and unsaturated C 5 ‐ to C 10 ‐alcohols were obtained at source temperatures ranging from 60° to 250°C. The reactivity of the ammonia adduct ion M NH and its fragmentation channels are characteristic for substrate structure. Although strongly temperature‐dependent, the spectra give nevertheless information on the OH‐group environment as well as on the C‐skeleton at any source temperature. Primary, secondary and tertiary alcohols as well as allylic and simple olefinic alcohols can be distinguished by their spectra, which show ammonium adduct ions [ M NH 4 ] + , adduct dehydrogenation ions [ M NH 4 ‐H 2 ], ammonium substitution ions [ M NH 4 ‐H 2 O] + and [ M ‐OH] + ‐ions as the main characteristic peaks. Moreover, konfigurational assignments of stereoisomeric alcohols are possible for larger substrate‐size and source‐temperature ranges than with isobutane CI mass spectrometry. Homologous M NH‐ions show molecular‐size control of fragmentation and linear M NH‐ions are less stable than branched isomers due to incomplete energy randomization.