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Negative ion mass spectrometry of phenothiazines
Author(s) -
Ryhage Ragnar,
Brandenberger Hans
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.1200051105
Subject(s) - chemical ionization , chemistry , reagent , electron ionization , ion , ring (chemistry) , mass spectrum , ionization , molecule , mass spectrometry , ion source , methylene , ionization energy , organic chemistry , chromatography
Mass spectra of a number of phenothiazines have been obtained by negative chemical ionization and compared with the corresponding mass spectra by positive chemical ionization and conventional electron impact. NH 3 , CH 4 and N 2 O were used as reagent gases for negative chemical ionization, iso‐C 4 H 10 and CH 4 for positive chemical ionization. The negative chemical ionization technique gives significant information regarding the molecular weight and the ring system of this group of compounds. As a complementary method to positive electron impact, negative chemical ionization is more informative than positive chemical ionization. Phenothiazines with two, but not three, methylene groups between the ring and the sidechain nitrogens give an intense rearrangement anion due to loss of the substituted nitrogen in sidechain and two additional hydrogens. A 5‐membered ring structure is postulated for this anion, which is formed with the reagents NH 3 and CH 4 , but not with N 2 O. Apart from this peculiarity, the negative chemical ionization spectra are easy to understand. With NH 3 as reagent, the anions representing the ring system and [M − 1] − dominate the anion current. With CH 4 , both quasimolecular ions[M + 1] − and [M − 1] − can be detected along with the much more intense ring anion. The reagent N 2 O yields cluster anions by oxidation of the ring and the molecule with the negatively charged oxygen formed in the ion source.