The IUPAC name of neopentane is:

• (A) 2,2-dimethylpropane
• (B) 2-methylpropane
• (C) 2,2-dimethylbutane
• (D) 2-methylbutane

To determine the IUPAC name of neopentane, we first need to understand its structure. Neopentane is a branched-chain alkane with five carbon atoms. The correct IUPAC name for neopentane is (A) 2,2-dimethylpropane. Let’s break down why this is the case.

Understanding Neopentane's Structure

Neopentane has the following structural formula:

• It consists of a central carbon atom bonded to four other carbon atoms.
• Two of these carbon atoms are attached as methyl groups (–CH₃) to the central carbon.

This arrangement gives neopentane its unique branched structure, which can be visualized as follows:

• Central carbon (C1) is connected to two methyl groups (C2 and C3) and two other carbon atoms (C4 and C5).

Identifying the Correct IUPAC Name

In IUPAC nomenclature, we start by identifying the longest continuous carbon chain. In the case of neopentane, the longest chain consists of three carbon atoms, which is a propane. The two additional carbon atoms are methyl groups attached to the second carbon of the propane chain. Therefore, we denote these substituents in the name:

• The base name is "propane" (for the three-carbon chain).
• Since there are two methyl groups on the second carbon, we use "2,2-dimethyl" to indicate their positions and quantity.

Putting it all together, we arrive at the name 2,2-dimethylpropane. This name accurately reflects the structure of neopentane, confirming that option (A) is indeed the correct answer.

Comparing with Other Options

Let’s briefly examine the other options to clarify why they are incorrect:

• (B) 2-methylpropane: This name suggests a straight-chain structure with one methyl group on the second carbon, which does not represent neopentane.
• (C) 2,2-dimethylbutane: This implies a four-carbon chain (butane) with two methyl groups on the second carbon, which is not the case for neopentane.
• (D) 2-methylbutane: Similar to option B, this suggests a straight-chain structure with one methyl group, which again does not match neopentane.

In summary, the IUPAC name for neopentane is 2,2-dimethylpropane, as it accurately describes the structure of this compound. Understanding the naming conventions and how to identify the longest carbon chain is crucial in organic chemistry, as it helps in recognizing and naming various organic compounds correctly.