The reactivity and behavior of phenol (phenol-d(5)) on NaX zeolite at different temperatures have been studied by H-1 MAS NMR and FT-IR techniques. An interaction between hydroxyl of phenol and zeolite framework oxygen atoms has been revealed, favouring the transfer of H(D) atoms of phenolic hydroxyl to zeolite framework to give phenolate ions. In phenol, the isotope exchange between H(D) atoms of phenolic hydroxyl and those of ring occurs mainly at ortho and para positions. The formation of phenolate ions changes the isotope exchange to meta position. The formation of phenol to phenolate ions is enhanced on NaX zeolite, explaining the high O-alkylation selectivity observed in phenol alkylation with methanol. (c) 2005 Elsevier B.V. All rights reserved.