Protocol for Structure Determination of Unknowns by EI Mass Spectrometry. III. Diagnostic Ions in Multiple Ring Carbo- and Heterocycles, and Mono-Functional Derivatives

Abstract

Electron ionization (EI) mass spectra of bi- and poly-ring carbo- and heterocycles including saturated and unsaturated spiranes, condensed ring and bridged ring systems are examined. Three, four, five, six-membered and larger rings are considered. The rings may include oxygen, sulfur, nitrogen, selenium or phosphorus atom or multiple hetero atoms. Characteristic fragmentation modes and diagnostically important ions generated by these compounds under EI are established. Detailed analysis of mass spectra of halides, alcohols and mercaptans, ethers and thioethers, aldehydes, ketones and thiones, carboxylic and thiocarboxylic acids, amines, amides and thioamides, nitro compounds, nitrites and nitrates of mono- and poly-ring carbo- and heterocyclic systems is performed. Basic fragmentation rules typical for a specific ring and general dissociation modes governed by a particular functional group are determined. The potential and its limitations of EI mass spectrometry in structure determination of unknowns are emphasized.