Intramolecular General Acid Catalysis of the Hydrolysis of 2-(2‘-Imidazolium)phenyl Phosphate, and Bond Length−Reactivity Correlations for Reactions of Phosphate Monoester Monoanions

Rate constants for the hydrolysis of 2-(2‘-imidazolium)phenyl hydrogen phosphate (IMPP) in water at
pH < 6 indicate that activation by the imidazolium moiety disappears with the deprotonation of the
phosphate group, and the reaction involves the hydrogen-bonding of the imidazolium NH with the aryl
oxygen leaving group. The reaction should involve a near-planar conformation of the imidazolium and
the phenyl groups in the activated complex, which favors proton-transfer. The crystal structure of IMPP
was solved, and a bond length−reactivity correlation for reactions of phosphate monoester monoanions
is described.