Reaction Of Benzoate Research Articles

A metal–organic framework via the reaction of benzoate with a cationic inorganic material

Our research group previously reported a two-dimensional cationic inorganic material (BING-5, Pb(3)F(5)NO(3)) where nitrate resides in the interlamellar space and can be anion exchanged. Investigation of the possible exchange of nitrate for benzoate led to the discovery of a layered metal-organic framework, lead benzoate hydrate [Pb(C(6)H(5)CO(2))(2)(OH(2))]. The compound crystallizes as colourless plates in the monoclinic space group P2(1)/c. The two dimensional lead-oxygen layers contain bridging benzoate oxygen atoms, with bridging water molecules further supporting the layers. The benzoate molecules are positioned perpendicular to the layers and form a hydrophobic bilayer region. The material shows basic character when immersed in various solvents suggesting potential as a base catalyst.

Unexpected Reaction of Benzoates with Chlorovinylsilanes in the Presence of Magnesium: A Facile Synthesis of (3-Oxo-3-phenyl)propylvinylsilanes and Further Transformations

Unexpected Reaction of Benzoates with Chlorovinylsilanes in the Presence of Magnesium: A Facile Synthesis of (3-Oxo-3-phenyl)propylvinylsilanes and Further Transformations

Rate Constants for Reaction of Hydroxyl Radicals with Water-Soluble Porphyrins and Metalloporphyrins.

To determine the rate constants for the reaction of hydroxyl radicals with water-soluble porphyrins and their metalloporphyrins, tetrakis(4-sulfophenyl)porphine(TPPS), tetrakis(5-sulfothienyl)porphine (T(5-ST)P), tetrakis(4-N-methylpyridyl)porphine (TMPyP) and tetrakis(4-N-trimethylamino-phenyl)porphine (TTMAP), and Mn(III), Fe(III), Co(III) and Cu(II) complexes of TPPS and TMPyP, the γ-irradiation method, in which the fluorescence of hydroxybenzoates produced through reaction of benzoate with hydroxyl radicals generated by water-radiolysis is measured, were tried. However, since the porphyrins and metalloporphyrins show the characteristic absorption spectra in the visible region, the fluorescence of hydroxybenzoate products was disturbed by the colors. To separate the hydroxybenzoates from the colored solute, the products were extracted into ether under an acidic condition. The hydroxybenzoates were extracted thoroughly into the ether layer from an aqueous layer of less than pH 3 ; the residue was redissolved in phosphate buffer, pH 7.5; the solution was used to determine the rate constants. The rate constants for anionic porphyrins, TPPS, T(5-ST)P, were in the order of 109, and the constants for cationic porphyrins, TMPyP, TTMAP, in the order of 1010. Metal complexes of TPPS and TMPyP showed the rate constants of 6.9 to 11.4×109M-1S-1 and of 3.2 to 19.7×109M-1S-1, respectively.

Hyaluronan-mediated protective effect against cell damage caused by enzymatically produced hydroxyl (OH.) radicals is dependent on hyaluronan molecular mass.

Hyaluronan (HA) protected tendon fibroblasts against cell damage mediated by hydroxyl radicals (OH.) as demonstrated by release of 51Cr from labelled cells. Protection afforded by high molecular mass (M(r)) HA (1218 kDa) was much more effective than that provided by lower (176 kDa and 668 kDa) M(r) HA. OH. was generated by coupling H2O2 produced by glucose oxidase:glucose to [Fe(2+)-EDTA] chelate in a Fenton-type system. The flux of OH. was measured by a spectrofluorimetric assay of salicylate produced by the reaction of benzoate with OH.. Cell damage caused by the OH. generating system was prevented in the presence of catalase, which destroyed H2O2. Damage caused in a standard incubation time increased with increased amounts of glucose oxidase. Protection against OH.-mediated cell damage increased with increasing concentration of HA. The presence of HA did not interfere with the enzyme-Fenton system, as monitored by production of gluconate. On the other hand, HA scavenged OH. produced by the enzyme-Fenton system, as shown by competition with benzoate, which produced less salicylate in the spectrofluorimetric assay in the presence of HA. The reaction of OH. with HA was measured directly by a pulse radiolysis technique in which a hydrated electron (eaq-) produced OH. by the reaction with nitrous oxide. Second order rate constants obtained in distilled H2O or in phosphate buffer showed no dependence on HA M(r). Similarly, fluorimetric assay of the flux of in the enzyme-Fenton system confirmed that HA competed with benzoate, thus lowering salicylate production, and the flux was also independent of the molecular mass of HA.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanism of Ester Aminolysis in Aprotic Media and Specific Solvent Effects

AbstractThe n‐butylaminolysis of nitro‐substituted 4′‐nitrophenyl benzoates and cinnamates as well as of phenylacetates in aprotic solvents is governed by a kinetic law implying higher order terms in nucleophile. It is shown that the attacking nucleophile forms a n‐π type molecular complex with the substrate before reaching the transition state in the subsequent kinetic step. This molecular complex is a true reaction intermediate as evidenced by the observed negative activation enthalpy. Other nucleophile molecules intervene as general base catalysts. Tertiary amines also catalyse the reaction. Their catalytic activity is linearly related to their hydrogen bond forming ability and it is not a direct function of their proton basicity. By varying the nucleophile structure, an excellent Brönsted relationship could be obtained for the first time in aprotic media, the ß of which confirms that the catalytic collapse of tetrahedral intermediate is the rate determining step. The reaction of cinnamates turns out to be less sensitive to structural changes of the substrate than is the reaction of benzoates as shown by the corresponding Hammet σ values. The electronic effects of 2‐nitro groups are strongly solvent dependent. Once more, it is established that whenever specific solvent effects (π‐donor or n‐donor ability) are present, they dominate the overall effect. A general reaction mechanism is proposed which not only explains the various roles played by the nucleophile but also accounts successfully for the great variety of kinetic schemes observed in aprotic media.

Kinetics of reaction of triethylammonium carboxylates with α-halogenocarbonyl compounds in organic solvents : Reaction of benzoates and phenoxyacetates with phenacyl bromide in acetone

The kinetics of the reaction of phenacyl bromide with triethylammonium p-substituted benzoates and phenoxyacetates at 25°, 30° and 35° in acetone suggest a rigid cyclic transition state involving a hydrogen bonded ion-pair as the active nucleophile. The effect of addition of water on the rate constant is rationalized. Regression analysis on single parameter treatment on benzoates shows that the reaction obeys the Hammett equation (ϱ value + 0.37, with r = 0.993).

Evidence for participation of NADH-dependent reductase in the reaction of benzoate 1,2-dioxygenase (benzoate hydroxylase).

Benzoate 1,2-dioxygenase which has so far been referred to as benzoate hydroxylase catalyzes the double hydroxylation of benzoate, namely the incorporation of two hydroxyl groups into benzoate, resulting in the formation of l,2-dihydro-l,2-dihydroxybenzoate (DHB). Both oxygen atoms of the two hydroxyl groups introduced into the substrate are derived from the molecular oxygen (1,2).

Studies on mechanism of double hydroxylation I. Evidence for participation of NADH-cytochrome [formula omitted] reductase in the reaction of benzoate 1,2-dioxygenase (benzoate hydroxylase)

Benzoate 1,2-dioxygenase system which catalyzed double hydroxylation of benzoate was obtained from Pseudomonas arvilla and was shown to consist of two protein components (component A and B). Component A which was purified and was shown to be homogeneous upon sodium dodecyl sulfate disc gel electrophoresis retained high activity of NADH-cytochrome c reductase. Both of benzoate 1,2-dioxygenase activity and NADH-cytochrome c reductase activity were simultaneously induced by benzoate. Dichlorophenolindophenol which could serve as an electron acceptor of the NADH-cytochrome c reductase inhibited the activity of benzoate 1,2-dioxygenase. These results suggest the possibility that NADH-cytochrome c reductase activity is required for benzoate 1,2-dioxygenase.