JMSSJ On-line, Vol. 50 (2002) No. 4, pp. 173-188
A Rule to Account for Mass Shifts in Fragmentations of Even-Electron Organic Ions in Mass Spectrometry
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    Hisao NAKATA*

    *Professor Emeritus, Aichi Kyoiku University (147-24, Arimatsu-ura, Narumi-cho, Midori-ku, Nagoya 458-0824, Japan)

  A rule of mass shift, which accounts for mass shifts in fragmentations of even-electron organic ions, is exemplified in detail. The term “mass shift” is defined as a mass difference between the mass of an observed ion and the mass calculated from the corresponding part of the structural formula of a sample molecule. According to the nature of the cleaved bond, the mass shift is either 0, +1, +2, or even +3 for positively charged fragment ions, and 0, -1, or -2 for negative ions. Rationalization of the rule is made on the basis of structural requirement of stable even-electron organic ions. The rule is shown to be valid not only for ordinary reactions of positive or negative ions but also for collision-induced dissociations and charge-remote fragmentations. Some mechanistic implication of fragmentations related to the rule is also discussed.

Key words:   Mass shift,Fragmentation,Even-electron ion, Fragment ion,Charge-remote fragmentation

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