153470-52-1Relevant articles and documents
Flash photolysis of α-diazonaphthoquinones in aqueous solution: Determination of rates and equilibria for keto-enol tautomerization of 1-indene-3-carboxylic acid
Almstead, Ji-In Kim,Urwyler, Bernhard,Wirz, Jakob
, p. 954 - 960 (2007/10/02)
Flash photolysis of either 1-diazo-2(1H)naphthalenone (1a) or 2-diazo-1(2H)naphthalenone (1b) generates benzofulven-8-one (2). Hydrolysis of ketene 2 forms benzofulvene-8,8-diol (3), the enol tautomer of indene-3-carboxylic acid (4). pH rate profiles for the reactions 2 → 3 and 3 → 4 were determined in aqueous solution. Ketonization of 3 is catalyzed by acid and by base. Catalysis by protons saturates in strongly acidic solutions, thereby defining the first ionization constant of the enol, pKaE = 1.90 ± 0.05, catalysis by hydroxyl ions saturates in dilute base, defining the second ionization constant, pK′aE = 8.3 ± 0.2. The first (OH) and second (CH) ionization constants of 4 were determined by spectrophotometric titration, pKaK = 4.50 ± 0.03 and pK′aK = 15.2 ± 0.2. Two independent estimates of the enolization constants of 4 and 4-, the first based on thermodynamic cycles, the second on the ratio of enolization and ketonization rates, were combined to give pKE = 9.3 ± 0.3, pK′E = 6.6 ± 0.3. Ketene 2 is formed by irradiation of 1-bromo-2-naphthol at 12 K in an argon matrix, but neither it nor its isomer 2-bromo-1-naphthol were suitable for the generation and observation of 2 and 3 by flash photolysis in aqueous solution.
