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A fundamental chemical reaction type involves the transfer of a proton from an acid to a base. Although proton transfer has been observed to occur in the gas phase only for clusters of base molecules, the electronic spectra of 1:1 acid-base complexes provide information about the nature of the interactions that occur along the reaction coordinate. We report here studies of the rotationally resolved spectra of the hydrogen bonded complexes of hydroquinone, 1-hydroxynaphthalene and 6-cyano-2-hydroxynaphthalene with $NH3$. Analyses of these spectra yield the heavy atom separations between the acid and the base and the barrier heights for the internal rotation of the $NH3$ group about its $C3$ axis, in both electronic states. Typically, upon $S1\leftarrow S0$ excitation, we observe a decrease in the heavy atom separation and an increase in the barrier to internal rotation. These changes provide information about the differences in the potential energy surfaces for proton transfer in the two electronic states.