Collisional activation spectra

Thiiranium salts, l-methyI-2-methylene-1-oxide, 7, 134 Thiiranium salts, I-phenyl-collisional activation spectra, 7, 135 Thiiranium tetrafluoroborate, 2,3-di-t-butyl-l-methyl-inversion barriers, 7, 134 Thiiranium ylides formation, 7, 174, 175 Thiiran-2-ones... 

Isomeric C Hn radical ions fragment not very differently by the different mass spectro-metric methods. The metastable decays are nearly identical, but the collisionally activated spectra of 14 isomeric hexenes, measured by Nishishita and McLafferty240, exhibit some quantitative differences. Bensimon, Rapin and Gaumann251 compared the metastable decay and the photoinduced fragmentation by infrared photons of long-lived parent ions of six hexene isomers and cyclohexane. If the linear isomers are practically identical, some notable differences are observed for branched isomers. Cyclohexane behaves similar to n-hexenes. The metastable fragmentation of H/D-labeled 4-Me-2-pentene, 2-Me-2-pentene... 

Tandem MS was applied to characterization and differentiation of the connectivity of the 0283 radical cation (mlz = 120) generated by dissociative electron ionization (El) of the l,3,4,6-tetrapentalene-2,5-dione 39. The structural assignment of the radical cation C2S as the C-sulfide ethenedithione, SCCS2 40, was based on the results of ion-molecule reactions of 0283 with nitric oxide, acetonitrile, and methyl isocyanide. The collisional activation spectra of these ion-molecule reaction products recorded on a new type of hybrid tandem mass spectrometer of sectors-quadrupole-sectors configuration allowed the confirmation of the ascribed structure 40 (Scheme 1) <1999PCA3666>. 

FIGURE 35. Collisional activation spectra (nitrogen collision gas) of the m/z 93 ions produced by electron ionization of aniline (a), and collisional deiodination of protonated 2-, 3- and 4-iodoaniline cations within the quadrupole collision cell (argon collision gas, Figures b-d). CS refers to charge stripping... 

The fragmentation pattern of (7) was discussed <82KGS765>. Collisional-activation spectra of (MOH ) and (MNO ) of 1-, 3-, 6- and 8-NO2—(8) were analyzed. They can be used to establish the position of the N02-group <88KGS1631>. 

J. T. Stults and J. T. Watson, Identification of a new type of fragment ion in the collisional activation spectra of peptides allows lencine/isolencine differentiation, Biomed. Environ. Mass Spectrom. 14, 583-586 (1987). 

Transient Three-membered Ring Compounds.—The existence of stable protonated alkylcyclopropanes as reactive intermediates has been discussed in detail. The collisional activation spectra of the gaseous ions formed upon protonation of pro-pene and cyclopropane are identical and the low activation energy for the conversion of protonated cyclopropane into the 2-propyl carbocation thus indicated is inconsistent with MINDO/3 calculations. Protonated cyclopropanes have been implicated in the reduction of (225) in the presence of strong acids and in the decomposition of cyclopropane on Zeolite HY. The involvement of the 3-methyl function in the deamination of 3-methyl-2-aminobutane has been evident for some time. However, studies with optically active and labelled substrates have now confirmed... 

Irradiation of thiophens in the presence of n-propylamine yields pyrroles, whose formation is explained by way of various three- and four-membered tricyclic sulphur-containing intermediate zwitterions. Cyclic C2H5S+ ions have been detected in the collisional activation spectra of cation radicals of thiols. ... 

---