Ammonium Hydroxide Does Not Exist Nitrogen has only four orbitals in its valence shell. No matter how the sand three p orbitals are hybridized, nitrogen can farm a maximum of anlv four bonds. If NHIOH existed. it would have to be 1005%ionized NHatOH-. Tetramethvlam. monium hydroxide does exist and is as strong a haae as sodium hydroxide. Phosphmuscan use theempty d orbitals in its valenceahell and makeapeeies that have nonitrogen equivalent,~uehsa phosphorus pentachloride and the hexafluomphosphate ion. Similarly s phosphine oxide can he written RIP=O, while an m i n e oxide is limited to R3N+-0-. Since both ammonia and water are polar and engage in hydrogen bonding, it is not surprising that they interact with each other. There are low-melting, solid hydrates of ammonia. In liquid aqueous ammonia, nuclear magnetic resonance studies have shown that the lifetime of a HzO ... . NH3 diffusion-controlled collision contact is about 10WQs. We should not mislead our students by writing ~
NH,OH(aq)
6
NH,'
~
+ OH-
but should always write NH,(aq)
+ H,O ==NH,' + OH-
Similarly, we should prevail on laboratory supply houses to stop labelling their bottles "ammonium hydroxide". It doesn't exist.
John Yoke Oregon State Unlverslty Cowallis. OR 97331
310
Journal of Chemical Education
