Mass spectral fragmentation alkenes

The mass spectral fragmentation pattern for (50) (70JHC639) and its X-ray crystal structure (78AX1136) have been reported. The most abundant spedes in the mass spectrum of (50) is the [yVf-56] ion which corresponds to the loss of four nitrogens. The X-ray picture of (50) indicates it is a planar molecule with a great deal of alkenic character assodated with the double bonds of the pyridazine ring. 

The determination of the position of the double bond in linear alkenes by oxyselena-tion and GC-mass spectrometry was described by Francis and Tande [265]. Mixed ethers containing oxygen and selenium, formed by single-step conversion of alkenes, showed mass spectral fragmentation characteristics that depend on the original doublebond position. 

Mass spectral peaks are often seen corresponding to loss of small, stable molecules. Loss of a small molecule is usually indicated by a fragment peak with an even mass number, corresponding to loss of an even mass number. A radical cation may lose water (mass 18), CO (28), C02 (44), and even ethene (28) or other alkenes. The most common example is the loss of water from alcohols, which occurs so readily that the molecular ion is often weak or absent. The peak corresponding to loss of water (the M-18 peak) is usually strong, however. 

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