Question 26.3: Writing the Formula to Correspond to the Name of an Alkane H...

General Chemistry: Principles and Modern Applications

Writing the Formula to Correspond to the Name of an Alkane Hydrocarbon

Write a condensed structural formula for 4-tert-butyl-2-methylheptane.

Analyze
The name tells us that the compound is a heptane with two substituent groups, tert-butyl and methyl, positioned at carbons 4 and 2, respectively.

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Because the compound is a heptane, the longest chain of C atoms is seven.

$\begin{matrix} C-C-C-C-C-C-C\end{matrix}$

Starting on the left, we attach a methyl group to the second C atom.

$\begin{array}{l} \ \ \ \underset{|}{\ \quad CH_3} \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \\ C-C-C-C-C-C-C\end{array}$

Next, we attach a tert-butyl group to the fourth C atom.

\begin{array}{l}\qquad \quad \ \ \ \ \qquad \qquad \qquad \ \qquad \qquad \ \underset{|}{\quad \ CH_3}\\ \quad\quad\quad\quad\ \ \ \ \ C-\overset{\large\overset{\quad \ CH_3}|}C-C-\overset{\large\overset{CH_3-C-CH_3}|}C -C-C-C \end{array}

Finally, we add the remaining hydrogen atoms to give each C atom four bonds.

\begin{array}{l}\qquad \qquad \qquad \qquad \qquad \ \qquad \ \ \ \ \ \underset{|}{\quad \ CH_3}\\ \qquad \qquad \ \ \ \ \ \ \ \ \ \ \ \ \ \underset{|}{\quad \ CH_3}\quad CH_3-\underset{|}{C} -CH_3 \\ \quad\quad\quad\quad\ \ \ \ \ CH_3-CH-CH_2-CH -CH_2-CH_2-CH_3 \end{array}

Assess
To check the answer, we use the nomenclature rules given on page 1152 to name the structure we’ve drawn. We should obtain the name that was given.

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