Question

IUPAC name of the compound $(\text{CH}_3)_4\text{C}$ is

• A. 2-Methylbutane
• B. Neopentane
• C. 2,2-Dimethylpropane
• D. 2-Methylpentane

Hint:

Be careful not to mix up common names and IUPAC names! "Neopentane" is a classic trap option because it is a correct name for the molecule, but the question explicitly asks for the systematic IUPAC name.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks for the formal IUPAC (systematic) name of the hydrocarbon structural formula given by $(\text{CH}_3)_4\text{C}$.

Step 2: Key Formula or Approach:
To determine the IUPAC name of a branched alkane, we use the standard IUPAC rules:
1. Find the longest continuous carbon chain to serve as the parent alkane.
2. Number the carbon chain from the end that gives substituents the lowest possible locant numbers.
3. Identify and name all alkyl groups attached as branches.

Step 3: Detailed Explanation:
The given condensed formula $(\text{CH}_3)_4\text{C}$ features a central carbon atom bonded to four surrounding methyl groups ($-\text{CH}_3$). Let's map out its layout:
$$\begin{array}{ccccccc} & & \text{CH}_3 & & \\ & & | & & \\ \text{CH}_3 & - & \text{C} & - & \text{CH}_3 \\ & & | & & \\ & & \text{CH}_3 & & \end{array}$$ The longest continuous straight path through this molecule contains exactly 3 carbon atoms. A 3-carbon alkane parent is called

propane.
Numbering this chain from left to right (C1, C2, C3) places the central carbon at position 2.
Looking at position C2, there are two separate single-carbon branches remaining (two methyl groups).
Combining these locants and branches together gives "2,2-dimethyl".
Assembling the full name gives 2,2-dimethylpropane. Note that while "neopentane" is the correct common trivial name, it is not the systematic IUPAC name. Therefore, option (C) is the correct choice.

Step 4: Final Answer:
The systematic IUPAC name of $(\text{CH}_3)_4\text{C}$ is 2,2-Dimethylpropane, corresponding to option (C).