Protocol for Structure Determination of Unknowns by EI Mass Spectrometry. I. Diagnostic Ions for Acyclic Compounds with up to One Functional Group
Anzor I. Mikaia
Abstract
This Review covers wide-ranging electron ionization (EI) dissociation reactions for various acyclic compounds and their derivatives, such as alcohols, aldehydes, ketones, carboxylic acids, amines, halides, thiols, thiones, esters, thioesters, amides, and more. Common derivatives of monofunctional compounds, such as trialkylsilyl, acyl, perfluoroacyl, oxazoline, and nicotinyl derivatives, are also discussed. The behavior of these under mass spectrometry (MS) conditions is determined, structures and stabilities of product ions are considered, and the ions of diagnostic power in their EI spectra are highlighted. Characteristic dissociation pathways for specific structural elements and their application for spectra/structure correlations are presented. Fundamental approaches for identifying unknowns are given. The advantages and limitations of EI-MS are emphasized. This knowledge is the key for successful applications of the exceptional capabilities of EI-MS for initial structure elucidation and then reliable structure determination of unknowns.