If a compound can't hydrogen bond with itself but can hydrogen bond with the water, why does it still remain immiscible?

Take for example ethoxyethane. It can't hydrogen bond with itself but its oxygen atoms can participate in hydrogen bonding with the slightly charged H atoms of the water.

So why does ethoxyethane still remain immiscible with water?

  • $\begingroup$ Because the gain in energy with bonding with ethoxyethane isn't worth it. The molecule is big compared to water. As a result, many hydrogen bonds with water are broken just in order to solvate ethoxyethane. In addition, ethoxyethane only has one site which it can hydrogen bond. $\endgroup$ Apr 24 '16 at 10:15

Ethoxyethane, better known as "diethyl ether" or even just "ether", can form hydrogen bonds with water. But fitting the ether molecules into the water solvent means you have to break up some water-water hydrogen bonds, and the ether molecules cannot replace enough of those hydrogen bonds to dissolve freely.

Of course, ether does form some hydrogen bonds, which makes is more soluble than it would be without the hydrogen bonds (compare ether with, for example, diethyl sulfide). But most (or at least the most common) freely water-soluble organic compounds have either ions to generate ion-dipole interactions with the water, or hydroxyl groups that readily fit with the hydrogen bonding structure of the water (think of ethanol or sugars).

  • $\begingroup$ Okay then please enlighten me on this. Do ethanol hydrogen bond with itself? $\endgroup$ Apr 24 '16 at 19:43
  • 1
    $\begingroup$ Absolutely yes. $\endgroup$ Apr 24 '16 at 21:11

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