Question 11.5: Writing IUPAC Names for Alkanes with Substituents Give the I...
Writing IUPAC Names for Alkanes with Substituents
Give the IUPAC name for the following alkane:
\begin{array}{r c}\begin{matrix} \quad {\underset{|}{{CH_{3}}}} \quad \quad \quad \quad {\underset{|}{{Br}}} \\ \quad \quad \quad \quad {CH_{3}}-CH-CH_{2}-C-CH_{2}-CH_{3} \\ \quad \quad \quad \quad \quad \quad \quad {\overset{|}{{CH_{3}}}} \end{matrix}\end{array}| Type of Compound | Substituent | IUPAC Naming | |
| ANALYZE THE PROBLEM |
alkane | two methyl groups, | number chain for |
| one bromo group | substituents |
Step \fbox{1} Write the alkane name for the longest chain of carbon atoms. In this alkane, the longest chain has six carbon atoms, which is hexane.
\begin{array}{r c}\begin{matrix} \quad {\underset{|}{{CH_{3}}}} \quad \quad \quad \quad {\underset{|}{{Br}}} \\ \quad \quad \quad \quad {CH_{3}}-CH-CH_{2}-C-CH_{2}-CH_{3} \\ \quad \quad \quad \quad \quad \quad \quad {\overset{|}{{CH_{3}}}} \end{matrix}\end{array} hexane
Step \fbox{2} Number the carbon atoms starting from the end nearer a substituent. Carbon 1 will be the carbon atom nearer the methyl group, —CH_{3}, on the left.
\begin{array}{r c}\begin{matrix} \quad {\underset{|}{{CH_{3}}}} \quad \quad \quad \quad {\underset{|}{{Br}}} \\ \quad \quad \quad \quad {CH_{3}}-CH-CH_{2}-C-CH_{2}-CH_{3} \\ \quad \quad \quad \quad \quad \quad \quad {\overset{|}{{CH_{3}}}} \end{matrix}\\\begin{matrix} 1&&2&&&3&&&&4&&&5&&6 \end{matrix} \end{array} hexane
Step \fbox{3} Give the location and name for each substituent (alphabetical order) as a prefix to the name of the main chain. The substituents, which are bromo and methyl groups, are listed in alphabetical order (bromo first, then methyl). A hyphen is placed between the number on the carbon chain and the substituent name. When there are two or more of the same substituent, a prefix (di, tri, tetra) is used in front of the name. Then commas are used to separate the numbers for the locations of the substituents.
\begin{array}{r c}\begin{matrix} \quad {\underset{|}{{CH_{3}}}} \quad \quad \quad \quad {\underset{|}{{Br}}} \\ \quad \quad \quad \quad {CH_{3}}-CH-CH_{2}-C-CH_{2}-CH_{3} \\ \quad \quad \quad \quad \quad \quad \quad {\overset{|}{{CH_{3}}}} \end{matrix}\\\begin{matrix} 1&&2&&&3&&&&4&&&5&&6 \end{matrix} \end{array} 4-bromo-2,4-dimethylhexane
Guide to Naming Alkanes
Step \fbox{1}
Write the alkane name for the longest chain of carbon atoms.
Step \fbox{2}
Number the carbon atoms starting from the end nearer a substituent.
Step \fbox{3}
Give the location and name for each substituent (alphabetical order) as a prefix to the name of the main chain.