Question

how to fragment the alkane in mass spectrometry​

Answer 1

Branched alkanes have a smaller molecular ion that at times may be

absent in highly branched compounds. In larger compounds branched

alkanes contain peaks at CmH2m+1, similar to straight chain alkanes. They are  distinguished by the lack of the smooth exponential decay beginning at the  C3 or C4 carbon (Figure 2.9). This is caused by the increased frequency of  fractionation at the branch since it results in a secondary rather than a  primary carbocation and is hence favored.

Explanation:

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