I’ve got a new category again. It’s called “Oddities”. I will put there chemical stuff that I find odd/weird/surprising/etc. They probably aren’t odd, weird or surprising to many of you but they are something that made me go “eh… wtf?”. This is the first oddities post.
The sulfone shown below is an intermediate I had during my project (sorry for the mystical “Ar” but I’m just being extra cautious with any unpublished results). The preparation of this intermediate was supposed to be fairly standard work with no surprises, and so there I was sitting in the NMR room running a standard H NMR to verify that it’s the right intermediate. And as soon as I see the spectrum I go “eh…wtf?”. Now pause for a moment and think how you would expect the H NMR (in d-chloroform) of that stuff to look like (you can ignore the Ar protons).
If you are thinking of something like two triplets (2H and 2H), then you are thinking exactly what I was thinking. However, there’s only one sharp singlet of 4 protons at around 4 ppm. I was, of course, quite surprised to see the singlet, so I ran a fast C NMR. Nothing weird there, one peak at 57 ppm and another at 35 ppm. After running some other experiments (e.g. HSQC) I was pretty convinced that the intermediate was ok. Eventually, I changed the solvent to d6-DMSO, and there they were, the triplets. I’m far from being an NMR expert so maybe one of you might want to explain the odd behavior in d-chloroform.