Question

Which of the following has the highest boiling point?
A. $1 - chloropen\tan e$
B. $2 - chloropen\tan e$
C. $3 - chloropen\tan e$
D. All have equal boiling point.

Answer 1

Hint : Branching lowers the surface area and hence lowers the boiling point. As the surface area decreases the interaction of molecules through vanderwaal forces decreases and hence lowers the boiling point. The compound having the largest surface area and less branching will have the highest boiling point.

Complete Step By Step Answer:
According to the question,
In the case of $1 - chloropen\tan e$ , it is a linear structure as the chlorine atom is attached to the first carbon atom of the chain which reduces the branching and hence has a large surface area. Due to this large surface area of the compound the van der waal forces increases between them and causes higher boiling point. Hence, $1 - chloropen\tan e$ has the highest boiling point.
In the case of $3 - chloropen\tan e$ , it is a branched structure, because chlorine is attached to the third carbon atom of the chain which decreases its surface area and thus decreases the van der waal forces which results in decreasing its boiling point. Hence, $3 - chloropen\tan e$ has a lower boiling point than $1 - chloropen\tan e$ .
In the case of $2 - chloropen\tan e$ , it is also a branched structure, because chlorine is attached to the second carbon atom of the chain which decreases its surface area and thus decreases the vanderwaal forces between them which results in lower the boiling point. Hence, $2 - chloropen\tan e$ has a low boiling point of $1 - chloropen\tan e$ .
So, option A is correct.

Note :
The boiling point of a liquid depends on the surrounding environmental pressure. A liquid in a partial vacuum has a lower boiling point than the liquid which is at atmospheric pressure. A liquid at high pressure has a higher boiling point than the liquid which is at atmospheric pressure. For example, water boils at ${100^o}C$ at sea level, but at ${93.4^o}C$ at $1905metres$ altitude. For a given pressure, different liquids will boil at different temperatures.