Plan
We first find the longest carbon chain and number it to give the substituent encountered first
the smallest possible number. Then we name the substituents as in Table 27-5 and specify the
number of each as indicated in Rule 4.
Solution
The longest chain contains five carbons, so this compound is named as a derivative of pentane.
There are two methyl groups, both at carbon number 2. The IUPAC name of this compound
is 2,2-dimethylpentane.
EXAMPLE 27-3 Naming Alkanes
Give the IUPAC name of the compound represented by the structural formula
Plan
The approach is the same as in Example 27-2. We should be aware that the longest carbon
chain might not be writtenin a straight line.
Solution
The longest chain contains six carbons, so this compound is named as a derivative of hexane.
There are three methyl substituents: two at carbon number 2 and one at carbon number 4.
The IUPAC name of this compound is 2,2,4-trimethylhexane.
You should now work Exercises 13 and 14.
EXAMPLE 27-4 Writing Formulas from Names
Write the structure for 4-tert-butyl-2,5-dimethylheptane.
Plan
The root name “heptane” indicates that there is a seven-carbon chain.
CXCXCXCXCXCXCThe names and numbers of the substituents tell us where to attach the alkyl groups.
CH 3 C CH 2 CH CH 3CH 3CH 3 CH 2CH 3CH 3 C CH 2 CH CH 2 CH 3CH 3CH 3 CH 3or(rewritten to emphasize the six-C chain)123 4561 2 3 4 56CH 3 C CH 2 CH CH 3CH 3CH 3 CH 2CH 3CH 3 C CH 2 CH 2 CH 3CH 3CH 31 23 4 527-2 Naming Saturated Hydrocarbons 1051