J. Chem. Research (S), 1997, 35 J. Chem. Research (M), 1997, 0355–0374 The Hydration of Indane-1,2,3-triones and Related Triones Keith Bowden* and Sanjay Rumpal Department of Biological and Chemical Sciences, Central Campus, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, UK A series of 5-mono- and 5,6-di-substituted indane-1,2,3-triones, phenalene-1,2,3-trione and 1,3-diphenylpropane- 1,2,3-trione form 2,2-dihydroxy-1,3-dione hydrates; the rates for the uncatalysed hydrations were measured and the structure of the transition state is elucidated from activation parameters, the kinetic role of water, and solvent isotope and substituent effects.The hydration of mono- and di-substituted indane- 1,2,3-triones (2), as well as of phenalene-1,2,3-trione and 1,3-diphenylpropane-1,2,3-trione, was investigated. The equilibrium constants and rate coefficients for mono-hydration, KH and k1, respectively, to form the substituted 2,2-dihydroxyindane- 1,3-diones (1) were estimated or measured.The results from 1H NMR and UV–VIS spectroscopic studies indicate that, in 0.7–96.7% (v/v) dioxane–water, the triones are almost completely (i.e. a98%) hydrated, cf. ref. 2. The rate coefficients, k1, for the uncatalysed hydration in dioxane–water (96.7%, v/v) were measured at 25.0, 35.0 and 45.0 °C. The activation parameters were evaluated with DH‡ between 4.0 and 6.6 kcal molµ1 and DS‡ between µ54 and µ46 cal molµ1 Kµ1. The effect of water content on the hydration rates in aqueous dioxane at 25.0 °C was studied.A plot of log k1 against log [H2O] was linear with a slope of 2.06. The kinetic solvent isotope effect, kH2O/kD2O, in dioxane–water (96.7%, v/v) was found to be 1.65 for 2a (X=Y=H). These results indicate two strongly hydrogen-bonded water molecules in the transition state and are very similar to the results found for dialdehydes.5 The application of a modified Hammett equation to the hydration of 2 gave a Hammett reaction constant (r) of ca. 1.05 in 96.7% aqueous dioxane at 25.0 °C. The latter indicates a significant extent of negative charge development at the reaction site in the transition state, relative to the initial state. A pathway is shown in the Scheme for the hydration of the triones with the transition state having one water molecule attacking the carbonyl group as a nucleophile and a second water molecule acting as a general acid– base catalyst transferring protons. Techniques used: UV–VIS, 13C NMR References: 25 Scheme: 1 Table 1: 13C NMR chemical shifts for the substituted indane- 1,2,3-triones and hydrates in [2H6]Me2SO Table 2: Rate coefficients (k1) for the hydration of substituted indane-1,2,3-triones in dioxane–water (96.7%, v/v) Table 3: Activation parameters for the hydration of substituted indane-1,2,3-triones in dioxane–water (96.7%, v/v) at 30.0 °C Table 4: Rate coefficients (k2) for the hydration of indane- 1,2,3-trione in aqueous dioxane at 25.0 °C Table 5: Hammett reaction constants (r) for the uncatalysed hydration of indane-1,2,3-triones in dioxane–water (96.7%, v/v) at 25.0 °C Table 6: The physical constants of the previously unreported substituted 2,2-dihydroxyindane-1,3-diones Table 7: The physical constants of the previously unreported substituted indane-1,2,3-diones Received, 25th October 1996; Accepted, 31st October 1996 Paper E/6/07281J References cited in this synopsis 2 W.Knoche, H. Wendt, M.-L. Ahrens and H. Strehlow, Collect. Czech. Chem. Commun., 1966, 31, 388. 5 K. Bowden, F. A. El-Kaissi and N. S. Nadvi, J. Chem. Soc., Perkin Trans. 2, 1979, 642; F. Anvia and K. Bowden, J. Chem. Soc., Perkin Trans. 2, 1990, 2093. J. CHEM. RESEARCH (S), 1997 35 *To receive any correspondence. Scheme