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348 CHAPTER 10 
 
To make the desired alkene (cyclohexene) from the 
starting compound (cyclohexane), we use the same 
approach taken in the solution to part (c). That is, we 
perform radical chlorination or bromination to install a 
leaving group, which then allows for an E2 process with 
a strong base to give the desired product. Once again, 
tert-butoxide will likely be more efficient, as it will 
suppress the competing SN2 process. In summary, the 
desired transformation can be achieved via the following 
three-step synthesis: 
 
 
 
(e) Radical bromination installs a bromine atom 
selectively at the tertiary position. Then, a strong base is 
used to give an E2 reaction (Zaitsev product, since the 
base employed is not sterically hindered): 
 
 
 
 
10.45. cis-1,2-Dimethylcyclopentane produces six pairs of compounds, where each pair have a diastereomeric 
relationship (except for one pair, which is enantiomeric, indicated below). In contrast, trans-dimethylcyclopentane 
produces only six different compounds, as shown below: 
 
 
 
 
10.46. 
(a) Recall that ΔG has two components: (ΔH) and 
(-TΔS). The first term is positive, so the second term 
must have a large negative value in order for ΔG to be 
negative (which is necessary in order for the process to 
be thermodynamically favorable). This will be the case 
if ΔS and T are both large and positive (T cannot be 
negative). At high T, both of these terms are indeed 
large. ΔS is large and positive because one chemical 
entity is being converted into two chemical entities, 
which significantly increases the entropy of the system. 
 
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