1) First, recognize that C6H5 is a phenyl group and makes a ring structure
(p.65). (I have found that when the ratio of carbon to hydrogen atoms are low
there are probably going to be double bonds or a "compacting" of the molecule.
If there are lots of H, single bonds will be used so there are enough
attachment sites for the H.)
2) I is attached at the carbon atom that lacks a H.
3) The names we have (so far) for rings are phenyl and benzyl and the benzyl
has a -CH2- attached so we go with phenyl--and the single Iodine is iodide ->
phenyl iodide.
ADDENDUM: Problem 2.21 k. l. & m have the wrong formula (given as C3H11N).
This is an example where the abundant H cannot be accommodated as there are not
enough attachment sites. The formula probably should be C3H9N which works
fine.
Hope this helps.
Kelly Mainard