Which of the following can hydrogen-bond with itself?

$\left(a\right)$ butane $\left(b\right)$ acetone $\left(c\right)$ acetic acid

May 29, 2017

Should be $\left(c\right)$.

While it's true that acetone, ("CH"_3)_2"C"="O" can hydrogen-bond with water, it can only form dipole-dipole interactions with itself.

Acetic acid, $\text{CH"_3"COOH}$, can hydrogen-bond with itself (very well, I might add!).

London Dispersion $<$ Dipole-Dipole $<$ H-"bonding" $<$ Ion-Dipole $<$ Ion Pair

...and recalling that as intermolecular force strengths increase, molecules stick together more and vaporize less easily (corresponding to a higher boiling point), we would then have that:

• since butane, ${\text{CH"_3"CH"_2"CH"_2"CH}}_{3}$, only has London Dispersion (being a hydrocarbon, a nonpolar molecule!), it has the lowest boiling point.
• since acetone has dipole-dipole interactions with ITSELF, it has the second-highest boiling point.
• since acetic acid hydrogen-bonds with ITSELF, it has the highest boiling point.

And we can't go without the data. From a quick Google search:

$- {1}^{\circ} \text{C}$ for butane
${56}^{\circ} \text{C}$ for acetone
${118.1}^{\circ} \text{C}$ for acetic acid

which follows the trend predicted above. Hence, the answer is $\left(c\right)$.