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

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SUMMARY

2-propanethiol has a lower boiling point than 1-propanethiol due to differences in molecular structure affecting intermolecular forces. The position of the thiol group (S-H) in 2-propanethiol disrupts the continuity of the hydrocarbon chain, leading to reduced Van der Waals forces compared to 1-propanethiol. This results in a smaller effective surface area for intermolecular interactions, further lowering the boiling point. The discussion highlights the significance of molecular geometry in determining boiling points.

PREREQUISITES
  • Understanding of molecular structure and geometry
  • Knowledge of intermolecular forces, specifically Van der Waals forces
  • Familiarity with boiling point concepts in organic chemistry
  • Basic principles of hydrophobic interactions
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Chemistry students, organic chemists, and anyone interested in the physical properties of organic compounds will benefit from this discussion.

jonahsaltzman
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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:
SHD5hNw.png
2-propanethiol:
Hydzs5F.png

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
 
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It might have something to do with surface area of the molecule
 
To add to Woopydalan comment: try to imagine two molecules lying side by side - their interactions should be proportional to the "contact surface".
 

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