Missing Ammonia Chemistry

Cats are great pets, but having them around means occasionally having to deal with cat pee. Years ago I had a male cat that for some reason began to spray inside the house. The problem eventually resolved itself, but not before I had plenty of urine-soaked towels that needed to be cleaned (or burned). Without thinking too much about it, I threw them in the washing machine along with some bleach. Now even my wife knows not to mix ammonia and bleach, but I didn’t make the connection until a rather noxious odor began emanating from the laundry room. Apparently, the amount of nitrogen in those towels was considerable.

While airing out the house, I was struck by the fact that I was unaware of the actual chemical reaction that had occurred. AFAIK, it had never been mentioned in any of my chemistry classes. In fact, I do not recall ever hearing much about ammonia chemistry at all, other than vague statements about ammonia being the nitrogen analogue of water. We covered amines in organic chemistry, but that was about it. Apparently, the chemistry of ammonia was just not considered important enough to teach. Other than using a metric ton of ammonium hydroxide over the years for raising pHs or making transition metal ammine complexes, I really had not had much interaction with ammonia. Anyway, as most of you probably already know, the ammonia/bleach reactions are:

NH₃ + HOCl → NH₂Cl + H₂O Toxic
NH₂Cl + HOCl → NHCl₂ + H₂O Toxic
NHCl₂ + HOCl → NCl₃ + H₂O Toxic and explosive

(Cat urine is mostly urea, I believe, but apparently Cl₂ can react with that too.)

In retrospect, I should have been aware of these reactions based on my “familiarity” with their iodine analogues. NI₃ is prepared using ammonia and iodine in exactly the same manner. Once dry, a slight touch is often sufficient to cause it to explode, producing a loud crack and a plume of purplish smoke. It’s probably fairly difficult to make it through undergraduate chemistry without learning this reaction (perhaps less so for organic chemists who have their own set of explosive materials with which to work). I admit to having used NI₃ in rather unprofessional ways as an undergraduate, but I was an amateur compared to the guy down the hall, who was known for producing rather large batches of NI₃ for his entertainment. My closest encounter with NI₃ occurred one evening, when this guy stopped by my lab to ask if I had enjoyed “the show.” Seeing the puzzled look on my face, he pointed to the various undetonated piles of NI₃ he had left throughout the lab which, by some miracle, I had managed to avoid. He also pointed to what appeared to be the remains of an already detonated batch of NI₃ on the inside of the doorknob - remains that I attempted to brush off with my finger. Well, my finger only tingled for a little while and it took some work to remove the iodine coating my hand, but otherwise I was no worse for wear. Needless to say, that guy never brought NI₃ into my lab again.

We definitely need to start teaching ammonia chemistry in school again.