First-order hyperpolarizabilities and pK_a of weak organic acids in protic solvents are lineraly related

Abstract

Second-order nonlinearities (β) of five weak organic acids in protic solvents have been measured by the double-quantum Rayleigh scattering (DRS) technique. β is found to bear a linear relationship to the pK_a of these compounds in those solvents. A direct implication of this observation is that the DRS technique can be used to determine the pK_a of weak organic acids in any solvent.