Question

Which one of the following molecules contains only primary and tertiary carbon atoms?

• A. 2,2-Dimethylbutane
• B. 3-Methylpentane
• C. 2,3-Dimethylbutane
• D. n-Hexane
• E. 2-Methylhexane

Answer 1

The Correct Option is C

In 2, 3-Dimethylbutane, the carbon atoms in the main chain are primary and tertiary. The carbon atoms attached to the methyl groups (at positions 2 and 3) are primary carbons, while the carbon at position 3 (in the backbone chain) is a tertiary carbon. This molecule contains only primary and tertiary carbon atoms, making it the correct choice. Other options include secondary carbon atoms, which do not meet the condition.

The correct option is (C) : 2,3-Dimethylbutane

Answer 2

2,2-Dimethylbutane

Explanation: 

To determine which molecule contains only primary and tertiary carbon atoms, we need to analyze the types of carbon atoms in each structure. Carbon atoms can be classified as:

• Primary (1°): A carbon atom attached to only one other carbon atom.

Let's analyze each compound:

• 2,2-Dimethylbutane: The central carbon in the butane chain is tertiary, and the two methyl groups (–CH₃) are attached to primary carbon atoms. This molecule contains only primary and tertiary carbon atoms.
• 3-Methylpentane: This molecule contains primary, secondary, and tertiary carbons, so it does not meet the condition.
• 2,3-Dimethylbutane: This molecule contains primary, secondary, and tertiary carbons, so it does not meet the condition.
• n-Hexane: This molecule contains primary and secondary carbon atoms, so it does not meet the condition.
• 2-Methylhexane: This molecule contains primary, secondary, and tertiary carbons, so it does not meet the condition.

Thus, the correct answer is 2,2-Dimethylbutane, as it contains only primary and tertiary carbon atoms.