Why does 2-propanethiol have a lower boiling point than 1-propanethiol

[jonahsaltzman]

Homework Statement

Consider 2-propanethiol, shown below. Would you expect its boiling point to be higher or lower than that of 1-propanethiol? Why?

Homework Equations

1-propanethiol:

2-propanethiol:

The Attempt at a Solution

I looked it up, and 2-propanethiol does have a lower boiling point than 1-propanethiol, I just can't figure out why. I would have said that moving the S-H group to the middle of the molecule "interrupts" the hydrophobic region of the compound, but the question is referring to pure solutions, so there's no water to not interact with. My next best guess is basically the same thing, but instead of hydrophobic interactions, its Van der Waals forces. Meaning, instead of the entire hydrocarbon chain acting as one unit with a large number of electrons to be displaced, it is broken up into two units with fewer electrons each. But that really doesn't seem like a good explanation. Any ideas? Thanks so much!

Jonah

 

[member 392791]

It might have something to do with surface area of the molecule

 

[Borek]

To add to Woopydalan comment: try to imagine two molecules lying side by side - their interactions should be proportional to the "contact surface".