1
$\begingroup$

Why does butanoic acid have a higher boiling point then isobutyric acid, when they have similar molar mass and molecular structure?

Butanoic acid ($\ce{C4H8O2}$) has a molar mass of 88.11 g/mol, the boiling point is 163 °C, and intermolecular force of H-bond.

enter image description here

Isobutyric acid ($\ce{C4H8O2}$) has a molar mass of 88.11 g/mol, the boiling point is 155 °C, and intermolecular force of H-bond.

enter image description here

Improve this question
$\endgroup$
1
  • 4
    $\begingroup$ Same reason why n-Butane has a higher boiling point than Isobutane: More intermolecular van der Waals interaction. $\endgroup$ – Karl Sep 26 '15 at 9:59
2
$\begingroup$

In general, linear chains are more easily structured and packed than branched ones. You need more energy to disturb the more relatively packed structure.This could explain why butanoic acid has a higher boiling point than isobutyric acid, and yet they are isomers.

Improve this answer
$\endgroup$
2
  • $\begingroup$ Structuring and packing is usually an argument when talking about the melting point, right? How relevant would it be for liquid $\to$ gas? $\endgroup$ – Eashaan Godbole Mar 6 '19 at 14:26
  • $\begingroup$ There is higher energy needed to get away from liquid. $\endgroup$ – Poutnik May 21 '19 at 5:42

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.