ISSN:
0030-493X
Keywords:
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Pure [CH2CHCH2]+ and \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm{CH}}_{\rm{3}} \mathop {\rm{C}}\limits^{\rm{ + }} = {\rm{CH}}_{\rm{2}} $\end{document} ions are generated only in metastable fragmentations of [CH2=CHCH2X]+·, X=Cl, Br, I, and [CH3CX=CH2]+·, X=Br, I, respectively. For ion source generated [C3H5]+ ions there is some structural interconversion. The structure characteristic feature of their collisional activation mass spectra is the ratio m/z 27 ([C2H3]+): m/z 26 ([C2H2]+·). For \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm{CH}}_{\rm{3}} \mathop {\rm{C}}\limits^{\rm{ + }} = {\rm{CH}}_{\rm{2}} $\end{document} the ratio is only weakly dependent upon the translational energy of the ion. For [CH2CHCH2]+, the ratio rises sharply as translational energy is reduced, from 0.9 at 8 kV to c. 3 at 1 kV. [CH2CHCH2]+ ions generated by charge reversal of [CH2CHCH2]- show higher ratios, resulting from their lower average internal energy content. It must therefore be emphasized that [C3H5]+ ion structure assignments should only be made using reference data which apply to specific experimental conditions. [C3H5]+ daughter ion structures for a number of well-known fragmentations have been established. The heat of formation of the 2-propenyl cation was measured to be 969±5 kJ mol-1. Labelling experiments show that at low internal energies, allyl cations do not undergo atom randomization in c. 1-2 μs; high internal energy ions of longer lifetime (c. 8 μs) show complete atom randomization. H· atom loss from [13CH3CH=CH2]+· has been shown to generate [13CH2CHCH2]+ and \documentclass{article}\pagestyle{empty}\begin{document}$ {}^{{\rm{13}}}{\rm{CH}}_{\rm{2}} \mathop {\rm{C}}\limits^{\rm{ + }} - {\rm{CH}}_{\rm{3}} $\end{document} without any skeletal rearrangement.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/oms.1210181219
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