CH908, Problem set 3
1. Interpret the following spectra, draw reasonable structures and
assign as many peaks as possible:
a.
b.
c. note: this is not the same as b.
d. Elemental composition is given as C8H18O
e.
f.
2. A product ion mass or neutral loss of 91 Da indicates what
moiety? Why? Draw the structures.
C7H7•, Toluyl or tropylium (7 membered aromatic ring).
3. In EI ions, where are the charge site and the radical site located
initially? Why? Do they stay together during fragmentation?
First non-bonding electrons from heteroatoms, then pi bonding
electrons, then sigma bonding electrons. This simply follows the
energetics of electron binding. The charge site and radical site
almost always move apart in the fragmentation because the
electron-pushing rules are different for charges and radicals
(hemolytic vs. heterolytic bond cleavage)
4. Define the terms 'distonic ion' and 'charge remote fragmentation'.
Distonic ion: an radical ion where the charge and radical are at
different positions.
Charge remote fragmentation: fragmentation that is in a distant part
of the molecule from the charge, usually caused by long-range
radical rearrangements (hydrogen abstraction)