Kinetic and thermodynamic parameters for ferrate(VI) oxidation of phenol have been measured in isotopic solvents, H 2 O and D 2 O, using ambient and high-pressure stopped-flow UV-visible spectroscopy. An increase (fast stage) and then a decrease (slow stage) in absorbance at 400 nm are observed when potassium ferrate (K 2 FeO 4 ) and aqueous phenol solutions are mixed rapidly. This suggests that small amounts of unstable intermediate 4,4′-biphenoquinone are produced during this redox process. An electron paramagnetic resonance signal for the reaction mixture of ferrate and phenol trapped by spin-trap R-(4-pyridyl-1-oxide)-N-tertbutylnitrone indicates a radical reaction pathway. Gas chromatographic/mass spectrometric measurements show p-benzoquinone is a major organic product, and the red ferric thiocyanate complex formed from addition of potassium thiocyanate to the spent reaction solution indicates that Fe(VI) is reduced to Fe(III). Activation enthalpy, entropy, and volume changes have been determined. There is a primary isotope effect for the formation of the intermediate (fast stage), k fast (H 2 O)/k fast (D 2 O) ) 2.4 ( 0.6. Because the phenol hydroxylic hydrogen is deuterated in D 2 O, this isotope effect suggests that a hydrogen bond is formed in the transition state.

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Two new titanium silicate molecular sieves, designated ETS-10 and ETAS-10. have been ion-exchanged with Fe(II1). Both products exhibit prominent EPR signals, at g 6.0 and 4.3, that are assigned to populations of ferric iron on the surface and in the interior cavities, respectively, of the molecular sieve microcrystals. Corollary XPS measurements on these samples indicate that a substantial fraction of the surface iron is present as Fe(I1). Chemical modification procedures have been explored in an effort to produce ion-exchanged materials containing no exterior iron. Acid treatment (pH 1.0) proved to be an effective means of achieving this goal in the case of ETS-10-based materials. ETAS-10-based samples do not retain their crystallinity under these conditions.

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