Chapter 13, Problem 13.34P

$\text{2, 3-Dimethylbutane}$ and $\text{2, 2-dimethylbutane}$ have the same molecular ion in the mass spectrum, but

only one of these isomers gives a significant fragment at $m\text{/}z=57$ (a) Which isomer shows an intense

peak at $m\text{/}z=57$? (b) Propose a structure for the ion that gives rise to this peak. (c) The base peak in

the mass spectrum of the other isomer occurs at $m\text{/}z=43$ What ion gives rise to this peak?