Question

Which of the following has the highest boiling point?
A.2-Methylpentane
B.2,3-Dimethylbutane
C.2,2-Dimethylbutane
D.Cannot be determined

Answer 1

In order to find out the highest point among different organic compounds we should know the boiling point shows the strength of forces between molecules. The more they stick together, the more energy it will require to transform liquid into vapors.

Complete answer:
- We should first understand the concept of boiling point. As we increase the number of carbons in a compound, boiling also increases. Branching decreases the boiling point.
- We should know that the normal boiling point of a compound is an indicator of the volatility of that compound. The higher the boiling point, the less volatile is the compound. Conversely, the lower the boiling point, the more highly volatile is the compound.
- At a given temperature, if a compound’s normal boiling point is lower, then that compound will generally exist as a gas at atmospheric pressure.
- If the boiling point of a compound is higher, it then exists as a liquid or a solid.
- The boiling point of alkane is dependent on the chains of atoms and the molecular mass of the molecule. Branched-chain molecules have comparatively less boiling point than straight chain molecules.
- Therefore, the order of boiling point is shown below
2-Methylpentane < 2,3-Dimethylbutane < 2,2-Dimethylbutane

Note:
Boiling point of a liquid varies with the surrounding atmospheric pressure. A liquid at a higher pressure has a higher boiling point than when that liquid is at lower atmospheric pressure.