Phenyl-substituted 1-arylazo-2-naphthols (AAN) display (HN)-H-...-N=C-C=O-... reversible arrow N-...=N-C= C-OH... ketohydrazone-azoenol tautomerism and can form intramolecular resonance-assisted H-bonds from pure N-(HO)-O-... to pure (NH)-H-...-O through tautomeric and dynamically disordered N-(HO)-O-... reversible arrow (NH)-H-...-O bonds according to the electronic properties of their substituents. Three compounds of this series (m-OCH3-AAN = mOM; p-Cl-AAN = pCI; and p-NMe2-AAN = pNM2) have been studied by X-ray crystallography at four temperatures (100-295 K), showing that the remarkably short H-bonds formed (2.53 <= d((NO)-O-...) <= 2.55 angstrom) are a pure N-(HO)-O-... in mOM, a dynamically disordered mixture in pCl (N-(HO)-O-...:(NH)-H-...-O = 69:31 at 100 K), and a statically disordered mixture in pNM2 (N-(HO)-O-...:(NH)-H-...-O = 21:79 at 100 K). These compounds, integrated by the p-H-, p-NO2-, p-F-, and p-O--substituted derivatives, have been emulated by DFT methods (B3LYP/6-31+G(d,p) level) with full geometry optimization of the stationary points along the proton-transfer (PT) pathway: N-(HO)-O-... and (NHO)-H-...-O-... ground states and (NHO)-H-...-O-... transition state. Analysis of DFT-calculated energies and geometries by the methods of the rate-equilibrium Marcus theory shows that all H-bond features (stability and tautomerism, as well as position and height of the PT barrier) can be coherently interpreted in the frame of the transition-state (or activated complex) theory by considering the bond as a chemical reaction (NHO)-H-...-O-... reversible arrow (NHO)-H-...-O-... reversible arrow (NHO)-H-...-O-... which is bimolecular in both directions and proceeds via the (NHO)-H-...-O-... PT transition state (the activated complex).