Determination of daughter ion elemental compositions in charge separation reactions

Abstract

It is shown that the elemental composition of a product ion generated from a multiply charged ion in a charge separation reaction can be determined with a double focusing instrument under conditions of high mass and energy resolution. Results for a number of charge Separation reaction$ in benzylamine are briefly discussed.Useful structural information can be obtained from the estimation of the intercharge distance in doubl charged ions decomposing according to the reactionThis type of reaction is generally studied in compounds containing one or more. hetero atoms which facilitates the accommodation of the two positive charges.' A problem frequently encountered in this connection is the determination of the elemental composition of the ions [m2]+ and [m3]+ generated in these charge separation reactions.We wish to report that these elemental compositions can be established unambiguously from the presence of satellite peaks in an accelerating voltage scan under conditions of high energy resolution.Due to the mutual repulsion of the two positive charges, ions [m2]' and [m3]' generated from a doubly charged ion will have a somewhat higher kinetic energy than those generated from a singly charged precursor. In spectra taken with a single focusing instrument this results in the formation of satellite peaks to the high mass side of the normal peak^;^,^ a well known example is the [CH3]+ ion the spectrum of benzene, which is accompanied by an intense satellite peak due to the reaction: [7812+ -+ [63]++[15]'.3 These satellites are not observed in spectra obtained with a double focusing instrument because of its energy f ocusine properties.They can, however, be detected easily by setting the magnet current to collect the main beam of ions at a selected mle value and performing a narrow scan of the accelerating voltage under conditions of high energy resolution. Ions of the same elemental composition generated in tbe ion source from the decomposition of a doubly charged ion are then observed as satellite peaks at the low voltage side of the main beam of ions. This is shown in Fig. 1

Mass Spectra of Furfuryl Aldoximes and Ketoximes

“…The acylfurans thus obtained reacted with hydroxylamine to give the oximes (1)(2)(3)(4)(5)(6)(7)(8). 16 The compounds 9 and 10 were the products of the reaction of ethyl Iurfurylcarboxylate and the corresponding amines at 25°Cand then purified by vacuum distillation.…”

“…The first one is loss of R'CNO accompanied by transfer of hydrogen to the ring from the hydroxyl group to form an odd-electron furfuryl radical cation, a, as in the case of aromatic aldoximes.V'" This process is favored for a larger R' group because of formation of a more stable neutral alkyl isocyanate. However, the competitive process to remove a methyl group from the ethyl group (2,5,8) retards the formation of a. Another simple pathway is a transfer of the ring from the oxime group to form the furfuryl cation b, which is also generated from ion c. The loss of a methyl group from R (2,5,8) invariably reduces the ion peak intensities of a and b.…”

“…However, the competitive process to remove a methyl group from the ethyl group (2,5,8) retards the formation of a. Another simple pathway is a transfer of the ring from the oxime group to form the furfuryl cation b, which is also generated from ion c. The loss of a methyl group from R (2,5,8) invariably reduces the ion peak intensities of a and b. The third process, loss of a hydroxyl radical to form [M-17j+, c, and the following cleavage is important for compounds in this series.…”