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448 CHAPTER 13 
 
four ways to assemble a four-carbon substituent. These 
options result in four possible ethers, shown below, 
along with their common and systematic names. 
 
 
 
The common names of the four butyl groups were 
discussed in Section 4.2. The systematic name of each 
compound uses the longest continuous carbon chain as 
the parent and treats the methoxy group as a substituent 
in all four cases. 
Now let’s consider the possibilities when R has two 
carbon atoms and Ŕ has three carbon atoms. There is 
only one way to have a two-carbon substituent, but there 
are two ways to assemble a three-carbon substituent 
(propyl or isopropyl). These options result in two 
possible ethers, shown below, along with their common 
and systematic names. The common names of the two 
propyl groups were discussed in Section 4.2. Each 
systematic name uses the longest continuous carbon 
chain as the parent (propane) and treats the ethoxy group 
as a substituent. 
 
 
 
13.4. 
(a) The cation is potassium, so we must use 18-crown-6, 
which solvates potassium ions. 
 
 
 
(b) The cation is sodium, so we must use 15-crown-5, 
which solvates sodium ions. 
 
 
 
(c) The cation is lithium, so we must use 12-crown-4, 
which solvates lithium ions. 
 
 
 
(d) The cation is potassium, so we must use 18-crown-6, 
which solvates potassium ions. 
 
 
 
13.5. 
(a) A Williamson ether synthesis will be more efficient 
with a less sterically hindered substrate, since the process 
involves an SN2 reaction. Therefore, in this case, it is 
better to start with a secondary alcohol and a primary 
alkyl halide, rather than a primary alcohol and a 
secondary alkyl halide: 
 
 
(b) In this case, it is better to start with a secondary 
alcohol and a primary alkyl halide, rather than a primary 
alcohol and a secondary alkyl halide: 
 
 
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