The IUPAC name of $\mathrm{CH}_3 \mathrm{COCH}\left(\mathrm{CH}_3\right)_2$ is
The IUPAC name of $\mathrm{CH}_3 \mathrm{COCH}\left(\mathrm{CH}_3\right)_2$ is
2-methyl-3-butanone
4-methylisopropyl ketone
3-methyl-2-butanone
Isopropylmethyl ketone
Solution
To determine the IUPAC name of the compound $\mathrm{CH}_3 \mathrm{COCH}\left(\mathrm{CH}_3\right)_2$, we should follow the steps for naming ketones according to IUPAC rules:
1. Identify the Functional Group:
The compound contains a ketone functional group, indicated by the carbonyl group ($\mathrm{C}= \mathrm{O}$) bonded to two carbon atoms.
2. Determine the Longest Carbon Chain:
Identify the longest continuous chain of carbon atoms that includes the carbonyl group. In this compound, the longest chain containing the carbonyl group is four carbon atoms long. The chain is: $\mathrm{CH}_3 - \mathrm{C} - \mathrm{C} - \mathrm{CH}_3$.
3. **Number the Carbon Chain:**
Number the carbon atoms in the chain starting from the end closest to the carbonyl group to give it the lowest possible number. Thus, the carbonyl carbon is at position 2:
$
\begin{array}{c}
\mathrm{CH}_3 - \mathrm{CO} - \mathrm{CH}(\mathrm{CH}_3) - \mathrm{CH}_3 \\
1 \quad\quad\quad\quad 2 \quad\quad\quad 3 \quad\quad\quad 4
\end{array}
$
4. Identify and Name Substituents:
There is a methyl group ($\mathrm{CH}_3$) attached to the third carbon atom of the chain.
5. **Combine the Elements of the Name:**
- The parent chain is a four-carbon chain with a ketone, so the base name is "butanone."
- The ketone group is at position 2, so it is "2-butanone."
- The methyl substituent is at position 3, so it is "3-methyl."
6. Write the Complete IUPAC Name:
Combine the substituent name and the base name: "3-methyl-2-butanone."
Therefore, the IUPAC name of the compound $\mathrm{CH}_3 \mathrm{COCH}\left(\mathrm{CH}_3\right)_2$ is **3-methyl-2-butanone**.
The correct answer is Option C: 3-methyl-2-butanone.