Proton Sponge (Clean-up in round bottom five...)

You know a compound has a story when nobody calls it by a chemically descriptive name (or the inventor's name). Proton sponge, or 1,8-bis(dimethylamino)naphthalene, is one such compound.

Proton sponge was discovered in Roger Alder's lab in 1968. It is a non-nucleophilic base (like DBU), which, as mentioned before, is something that's often useful in synthesis (take, for example, the use of Hunig's base when using phosphoramidite chloride in preparing monomers for automated DNA synthesis). It is unusual, however, for at least one other reason. Aromatic amines are normally terrible bases; proton sponge is about 6 pKa units (10^6 times) more basic.

Predictably, while everyone else was spending the late 1960's hanging out in Haight-Ashbury and smoking whatever was available, chemists began to fret and toil over just what made proton sponge so basic. Steric clash in the unprotonated state (which is ostensibly relaxed by protonation and conformational change) and low-barrier hydrogen bonding have been invoked to explain it. My work touches on these areas, but I'm far enough removed to not know where people are on it these days. Proton sponge is one of my favorite compounds, and I have been following the LBHB theory for awhile (which has been invoked by many to explain the catalytic efficiency of serine proteases. People still disagree on that one.)

I'd love to hear anything anyone has to say about LBHB theory, proton sponge, etc.!