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Selective reagents in chemical ionization mass spectrometry: Tetramethylsilane with ethers
Author(s) -
Orlando Ron,
Ridge D. P.,
Munson Burnaby
Publication year - 1988
Publication title -
organic mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0030-493X
DOI - 10.1002/oms.1210230706
Subject(s) - chemistry , ether , adduct , mass spectrum , alkyl , mass spectrometry , ion , chemical ionization , reagent , polyatomic ion , tetramethylsilane , trimethylsilyl , molecule , medicinal chemistry , ionization , organic chemistry , chromatography
Chemical ionization mass spectra of several ethers obtained with He/(CH 3 ) 4 Si mixtures as the reagent gases contain abundant [M + 73] + adduct ions which identify the relative molecular mass. For the di‐ n ‐alkyl ethers, these [M + 73] + ions are formed by sample ion/sample molecule reactions of the fragment ions, [M + 73 − C n H 2 n ] + and [M + 73 − 2C n H 2 n ] + . Small amounts of [M + H] + ions are also formed, predominantly by proton transfer reactions of the [M + 73 − 2C n H 2 n ] + or [(CH 3 ) 3 SiOH 2 ] + ions with the ethers. The di‐ s ‐alkyl ethers give no [M + 73] + ions, but do give [M + H] + ions, which allow the determination of the relative molecular mass. These [M + H] + ions result primarily from proton transfer reactions from the dominant fragment ion, [(CH 3 ) 3 SiOH 2 ] + with the ether. Methyl phenyl ether gives only [M + 73] + adduct ions, by a bimolecular addition of the trimethylsilyl ion to the ether, not by the two‐step process found for the di‐ n ‐alkyl ethers. Ethyl phenyl ether gives [M + 73] + by both the two‐step process and the bimolecular addition. Although the mass spectra of the alkyl etherr are temperature‐dependent, the sensitivities of the di‐alkyl ethers and ethyl phenyl ether are independent of temperature. However, the sensitivity for methyl phenyl ether decreases significantly with increasing temperature.