We have already reported on the existence of well defined small protonated water clusters in acetonitrile using IR spectroscopy (Kalish et al., J. Phys. Chem. A 115  (2011) 4063). Using NMR we are now able to corroborate the general solvation scheme we have proposed for the hydrated proton in acetonitrile as a function of the molar ratio between strong mineral acids and water,  n = [H2O]/[acid]. Clearly distinguishable by their respective chemical shifts are the two smallest protonated water clusters n = 1,2, H3+O, and the protonated water dimer, H2O(H+)H2O, which dominate the solution for n = 1, 2, 3. For larger n  a combined NMR and IR study indicate the gradual increase of the average protonated water cluster size as a function of n while the proton inner solvation core more closely retaining the characteristics of  a deformed protonated water dimer, (H2O-H+� OH2)s than that of the protonated water monomer (H3+O)s. In addition, measurements done in mixed H/D solutions clearly indicate H+  preference over D+ in the shared proton position in-between two water molecules.

Probing small protonated water clusters in acetonitrile solutions by <sup>1</sup>H NMR and IR spectroscopy

246th National Meeting (2013)

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Probing small protonated water clusters in acetonitrile solutions by 1H NMR and IR spectroscopy

Probing small protonated water clusters in acetonitrile solutions by ¹H NMR and IR spectroscopy