Question

Which of the following can hydrogen-bond with itself?

`(a)` butane
`(b)` acetone
`(c)` acetic acid

Answer 1

Should be `(c)`.

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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, `"CH"_3"COOH"`, can hydrogen-bond with itself (very well, I might add!).

By recalling the relative intermolecular forces and their strengths...

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, `"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^@ "C"` for butane
`56^@ "C"` for acetone
`118.1^@ "C"` for acetic acid

which follows the trend predicted above. Hence, the answer is `(c)`.