Basic Mass Spectral Reactions

Nearly every mass spectral reaction can be placed into one of two major categories 

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This concept is basically a means to force consideration of possible decomposition pathways and their resulting product stabilities and steric requirements. The limits of its simplifying assumptions, however, should be recognized in mass-spectral interpretation. Sometimes, especially for multiple-bond cleavages, either radical or charge-site initiation produces the same products the cyclic ion decompositions of Equation 4..10 can also be written (Equation 8.33) as a charge-site reaction. The substantial peak at m/z 56 in the spectrum of 2-methyl-... 

In contrast to IR and NMR spectroscopy, the principle of mass spectrometry (MS) is based on decomposition and reactions of organic molecules on theii way from the ion source to the detector. Consequently, structure-MS correlation is basically a matter of relating reactions to the signals in a mass spectrum. The chemical structure information contained in mass spectra is difficult to extract because of the complicated relationships between MS data and chemical structures. The aim of spectra evaluation can be either the identification of a compound or the interpretation of spectral data in order to elucidate the chemical structure [78-80],... 

Compound A, a hydrocarbon with M+ = 96 in its mass spectrum, has the 13C spectral data that follow. On reaction with BH3 followed by treatment with basic H2O2, A is converted into B, whose 13C spectral data are also given. Propose structures for A and B. 

The existence of 1,2-dioxetandione (6) is still arguable. It was postulated as an intermediate in the chemiluminescent decomposition of oxalates with basic peroxide (Eq. 9), a reaction first discovered for oxalic chloride. Although its isolation was claimed in this reaction, no characteristic spectral data could be documented. The report that this carbon dioxide dimer was detected by mass spectrometry was shown to be erroneous. Consequently, this elusive species has so far defied synthesis and detection, and it seems urgent and timely to reinvestigate this challenging problem. 

An important improvement in the calculation procedure for species-specific multiple spiking was obtained by introducing isotope pattern deconvolution (IPD). The difference from the conventional multiple-spiking technique is the use of isotopic abundances instead of isotope ratios for calculation. The measurement of additional isotopes not used for calculation of interconversion reactions provides internal correction for mass bias effects without the application of an external isotopic standard, but also correction for spectral interferences. The basic equations applied in IPD can be found in the literature [78], This new method is predominantly applied in speciation analysis, but also in metabolism studies using stable isotopes [97, 98]. For quantification of elemental species, including... 

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