Question

which of following has highest boiling point and why? 1) 2-methyl pentane 2) 2,3-dimethylbutane 3) 2,2-dimethylbutane

Answer 1

Answer: 2-methyl pentane has highest boiling point.

Explanation: This is because, it has the least branched chain structure as compared to 2,3-dimethylbutane and 2,2-dimethylbutane. Therefore, it has largest surface area and hence has the highest boiling point.

Answer 2

2-Methylpentane has the highest boiling point.

• The boiling point increases with a decrease in branching.
• 2,3-dimethyl butane has two alkyl groups attached to the straight parent chain.
• It has 2 branches.
• 2,2-dimethyl butane has two alkyl groups attached to the parent chain.
• It also has 2 branches.
• 2-methyl pentane has only 1 alkyl group. There are fewer branches in it.

Hence, 2-Methylpentane has the highest boiling point.