Good to see Charlie’s still at it

Good to see Charlie Perrin is still pumping out papers, and interesting ones to boot.  I knew him in grad school.  He’s got to be over 80.

This one —J. Am. Chem. Soc. 141, 4103 (2019) –is about something that any undergraduate organic chemist can understand (if not the techniques he used) — keto/enol tautomerism, in which the hydrogen bounces between two oxygens, so that, given N molecules in solution, N/2  have the hydrogen bound to one oxygen and N/2 have it bound to the other.

No so in what Charlie found — a compound where the hydrogen is smack dab in the middle.  Some fancy NMR techniques were used to show this.

Hydrogen bonds are extremely subtle (which is why we don’t understand water as well as we might).  Due to the small mass of the proton it isn’t appropriate to treat the proton in hydrogen bonded systems as a classical particle.  When quantum mechanics enters, aspects such as zero point motion, quantum delocalization and tunneling come into play.  These are called quantum nuclear effects (aka Ubbelohde effects).