a) Write down the structures of some molecular ions. Locate the charge at the most preferable position.
b) What is the statement of the even-electron rule?
Odd-electron ions (such as molecular ions and fragment ions formed by rearrangements) may eliminate either a radical or an even-electron neutral species, but even electron ions (such as protonated molecules or fragments formed by a single bond cleavage) will not usually lose a radical to form an odd-electron cation. In other words, the successive loss of radicals is forbidden.
c) What is the statement of Stevenson’s rule?
When a fragmentation takes place, the positive charge remains on the fragment with the lowest ionization energy.
d) Where will the charge reside according to Stevenson’s rule? Write down the structures of the prefered fragment ions upon cleavage of the bonds shown below: