What about oxonium ions, such as hydronium ion? Do these hydrogen bond with water?

If we see hydrogen bonding as a purely electrostatic phenomenon, then why not? Ammonium ion still has nitrogen bearing a partial negative charge. Of course it can interact with positively polarized hydrogens in an electrostatic way.

However, we also know that hydrogen bonding is partially covalent. So, it seems unlikely that the ammonium ion would be able to form any additional covalent bonds.

  • $\begingroup$ Do you mean through as a hydrogen bond donor or acceptor? $\endgroup$
    – jerepierre
    Dec 19 '14 at 17:14
  • $\begingroup$ @jerepierre either $\endgroup$
    – Dissenter
    Dec 19 '14 at 17:17

There is a detailed consideration of this issue in Hydrogen Bonding of the Ammonium Ion Journal of Molecular Structure 345 (1995) 77-81.

First, the try to be clear about what they mean by "hydrogen bond":

For the purposes of the discussion, a hydrogen bond is taken to be a specific short-range interaction in which the N-H bonds within the ammonium ion are significantly affected by the surrounding ions, and not simply electrostatic attraction.

They conclude that ammonium ions rotate too freely in water for significant hydrogen bonding to exist.

In gas phase calculations, they find that one water molecule hydrogen bonds to one ammonium ion (in other words, the dimer is hydrogen bonded), based upon the lengthening of the N-H covalent bond, but as you add 2, 3, and 4 water molecules, the N-H bond length returns to the free ammonium N-H bond length and the O --- H length increases.

  • 1
    $\begingroup$ "They conclude that ammonium ions rotate too freely in water for significant hydrogen bonding to exist." I wonder what this means for the hydrogen bonding of water with itself. Shouldn't water molecules be rotating too freely for H-bonding to exist as well then? $\endgroup$
    – jerepierre
    Dec 19 '14 at 18:26
  • $\begingroup$ @jerepierre The activation energy for water to reorient (16 KJ/mol) is more than for ammonium (12 kJ/mol), even though ammonium has twice as many H. They further point out that it takes 44 kJ/mol to remove a water molecular to the gas phase from liquid water, but 363 kJ/mol for an ammonium ion, and emphasis 12 is a small fraction of 363. $\endgroup$
    – DavePhD
    Dec 19 '14 at 18:39

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