The name of the compound CH$_3$C(CH$_3$)$_2$CH$_2$CH$_2$CH$_3$

Analyze the question: We need the IUPAC name of CH₃–C(CH₃)₂–CH₂–CH₂–CH₃.

Concept: To name an alkane:

1. Find the longest continuous carbon chain (this gives the parent name).
2. Number the chain from the end that gives the substituents the lowest numbers.
3. Name and locate the branches, using prefixes like di- for two identical groups.

Solution:

Write out the structure:

        CH3
        |
CH3 – C – CH2 – CH2 – CH3
        |
        CH3

• Longest chain: Start at one CH₃ on the left, go through the central C, then CH₂, CH₂, CH₃. That is 1 + 1 + 1 + 1 + 1 = 5 carbons, so the parent is pentane.
• Numbering: Number from the left so the branched carbon gets the lowest number. The central carbon is C-2. (Numbering from the right would put it at C-4.)
• Substituents: The central carbon carries two extra CH₃ groups, so there are two methyl groups on C-2.
• Name: 2,2-dimethylpentane

Check the molecular formula: C₇H₁₆, which fits an alkane with 7 carbons (5 in the chain + 2 methyl groups).

Why the other options are wrong:

• A (2-methylbutane) has only 5 carbons in total.
• B (2,2-dimethylbutane) has 6 carbons in total.
• C (2-methylpentane) has 6 carbons in total and only one branch.

Answer: D. 2,2-dimethylpentane

Tip: Always count the total carbons first. Chain carbons plus branch carbons must equal the total in the formula. Also, when two identical groups sit on the same carbon, repeat the number (2,2-) and use "di-".