Although 2,2-dimethylhexane has a molecular weight of 114 , no peak is observed at m/z=114. The base peak in the mass spectrum occurs at M57. 14.24a Your answer is correct. Draw the ion corresponding to the peak at m/z=57. Choose the correct explanation why the M15 peak is not the base peak. M-15 indicates the loss of an ethyl group. Although the loss facilitates the formation of a stable tertiary carbocation, it is less favored as ethyl radicals are less stable than primary radicals. M-15 indicates the loss of a methyl group. Although the loss facilitates the formation of a stable tertiary carbocation, it is less favored as methyl radicals are less stable than primary radicals. M15 peak indicates the loss of an ethyl group. The resultant ethyl radical is stable than primary radical. M-15 peak indicates the loss of a methyl group. Methyl radical is more stable than primary radical