Just when I feel like this chemistry stuff is starting to make sense to me, I learn something new that makes me feel like I don’t understand it at all. Maybe I’m not the only one. Maybe even the professional chemists feel the same way sometimes. With that in mind, it’s time for another episode of Molecular Mondays.
This month (February, 2018), a paper was published by the Royal Society of Chemistry that casts doubt on a longstanding assumption made by chemists. It involves the S-2 ion in aqueous solutions.
First off, this may have been the most amusing scientific paper I’ve ever had the pleasure of reading. No, the authors didn’t make any references to unicorns, but they did mention something about fairies at the bottom of a well, and then there was this delightful quote: “[…] there has been a growing awareness amongst solution chemists that the S-2(aq) emperor may have no clothes.”
As I understand it, the existence of an aqueous S-2 ion is the kind of thing that makes sense on paper. It allows chemists to easily balance their chemical equations, and it’s been included in textbooks and chemical computer databases for so long now that everyone just takes it for granted that the thing exists.
But apparently the experimental evidence of this particular ion was lacking, and aqueous solutions incorporating several different sulfide compounds did not produce any S-2 ions. At least not according to a Raman spectroscopic analysis.
Now as I’ve written before, papers like this should NOT be interpreted as final proclamations handed down from the ivory tower of science. Rather, this kind of paper should be understood as the beginning of a conversation among scientists. Does this S-2(aq) ion exist or not? If not, how many prior scientific studies need to be reexamined?
There will be further research, and perhaps a rebuttal will be published. Then there will be a rebuttal to the rebuttal, and so forth. But I think, regardless of how this plays out, that this is a good reminder that in science—as in life—what makes sense on paper does not necessarily work in the real world.