But what is the thought process in giving the bridged carbon a higher priority than the side chain? I'm following the directions in the book, to first check the atoms directly attached to the asymmetric C. Since the bridge and the left side-chain carbon are the same, it says to move along the chain. The bridge chain is:
C* --- CH2 --- CH
The side-chain is:
C* --- CH2 --- CH2 --- CH
How does the bridge get priority over the side chain?
It isn't the bridge that gets priority, it is the second carbon along that chain. Go one step at a time -
The bridge chain is:
C* --- CH2
The side-chain is:
C* --- CH2 (Identical to this point)
The next carbon for the bridge is the other assymetric carbon, which is attached to one hydrogen and two oxygens. The next carbon for the side chain is another methylene, attached to two hydrogens and one carbon. The bridge has priority.
Looking at the first point of difference, the bridge chain is:
C
/
C* --- CH2 ---
CH --- C
The side-chain is:
C* --- CH2 ---
CH2 --- C