Experimental confirmation of the Badger-Bauer rule in the protonated methanol clusters: weak hydrogen bond formation as a measure of terminal OH acidity in hydrogen bond networks.

We report a linear correlation between the OH stretch frequency shift of the protonated methanol cluster, H + (MeOH) n , upon the π-hydrogen bond formation with benzene and the enthalpy change in clustering of H + (MeOH) n to H + (MeOH) n +1 . This result suggests a new method to explore hydrogen bond strength in hydrogen bond networks.