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Recognition of functional groups by chemical ionization mass spectrometry
Author(s) -
Lin Yong Yeng,
Smith Leland L.
Publication year - 1978
Publication title -
biomedical mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0306-042X
DOI - 10.1002/bms.1200051103
Subject(s) - chemistry , adduct , chemical ionization , mass spectrum , isobutane , protonation , ion , mass spectrometry , polyatomic ion , reagent , ammonia , molecule , ion source , nucleophile , inorganic chemistry , ionization , analytical chemistry (journal) , organic chemistry , chromatography , catalysis
A means of recognition of functional groups in organic molecules using chemical ionization mass spectrometry is described. Mass spectra of 34 C 27 ‐steroids using methane, isobutane and ammonia as reagent gases are recorded and correlations with structure proposed. Ammonia chemical ionization spectra are most instructive, generally yielding abundant ions of four types: an ammonium adduct [M+ NH 4 ] + , an ammonia displacement ion [M + NH 3 ‐ X] + , a protonated molecular ion [M + H] + and an elimination ion [M ‐ X] + . Both the [M + H] + and [M ‐ X] + ions appear to derive from the ammonium adduct [M + NH 4 ] + , and the ion [M + NH 3 ‐ X] + derives by a nucleophilic displacement of an elimination fragment X by neutral ammonia. Steroid ketones and olefins give predominantly [M + NH 4 ] + and [M + H] + ions, whereas alcohols and esters give a three‐component pattern of [M + NH 4 ] + , [M + NH 3 ‐ X] + and [M ‐ X] + ions. Spectra derived using methane or isobutane as reagent gas contain three major ion types: the protonated molecular ion [M + H] + , the hydride abstraction ion [M ‐ H] + and the elimination ion [M ‐ X] + . Steroid ketones give the [M + H] + ion predominantly; the olefins give both [M + H] + and [M ‐ X] + ions. Steroid alcohols give [M + H] + , [M ‐ X] − ions. Recognition by these means of functionality in nonsteroid compounds appears also to be possible.