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• 2461-86-1 2,4,6-trinitrophenylacetone 

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Relevant academic research and scientific papers

The aci-nitro equilibrium of picrylacetone: A kinetic and thermodynamic study in 50:50 and 30:70 (v/v) H2O-Me2SO mixtures

Rates of deprotonation of picrylacetone (3a) by a variety of bases B (phenoxide and carboxylate ions, primary amines, OH-, H2O) and of reprotonation of the resulting carbanion (C-3a) by the conjugate acids BH have been measured in 50 : 50 and 30 : 70 (v/v) H2O-Me2SO mixtures at 25 °C. In contrast with the situation in phenol and amine buffers, where only one relaxation time corresponding to a simple equilibrium approach according to 3a + B ? C-3a + BH is observed, a fast equilibrium protonation of the carbanion C-3a is found to precede its conversion to 3a at low pH in a number of carboxylic acid buffers and HCl solutions. The resulting short-lived nitronic acid species C-3aH has been characterized by UV-Visible stopped-flow spectrophotometry and all data (pKaNO2H , pKaCH, pKT) pertaining to the aci-nitro equilibrium of 3a in the two solvent mixtures studied could be determined. A notable solvent effect shown to be consistent with the preferential stabilization of the large polarizable carbanion C-3a by Me2SO is observed on pKaNO2H and PKaCH, but not on pKT, on going from 50 to 70% Me2SO. The solvent dependence and the magnitude of the intrinsic reactivity of 3a, as determined from the Bronsted plots for the various types of catalysts in the two solvent mixtures, are also found to agree with C-3a being an sp2-hybridized carbanion whose negative charge is largely dispersed through the picryl ring.

The low intrinsic reactivity of picrylacetone: an index for the ?-acceptor capability of a 2,4,6-trinitrophenyl structure

Rates of deprotonation of picrylacetone, i.e., 2,4,6-trinitrophenylacetone 4, by a variety of bases B (phenoxide and carboxylate ions, OH-) and of protonation of the resulting carbanion (C-4) by the conjugated acids BH+ have been measured in a 50percentH2O-50percentMe2SO (v/v) mixture at 25 deg C.The intrinsic reactivity (in the Marcus sense) of 4, as determined from the Broensted plot for phenoxide reactions (βArO = 0.38) is low: logkArO0 = 2.37.This value is more typical for the formation of a strongly resonance-stabilized benzyl-type carbanion than for that of an enolate- type carbanion and it may be regarded as a good measure of the high ?-acceptor capability of a conjugated 2,4,6-trinitrophenyl structure.Definitve evidence that the negative charge of C-4 is essentially delocalized through the picryl moiety comes from the observation that this carbanion undergoes instantaneous protonation at its p-nitro group at low pH (pH a value associated with the ionization of the resulting nitronic acid (C-4H) is ca.5, which compares well with similar data previously reported in the literature.