COOH Radicals Research Articles

A study of the oxidation of adsorbed films formed on platinized platinum in methanol, formic acid and carbon dioxide solutions

Summary The oxidation of films formed on platinized platinum in methanol, formic acid and carbon dioxide solutions has been studied. It is shown that approximately one site is bared for every electron involved in the oxidation of these films. It is concluded that the same species is absorbed in all the cases studied and that it has the composition HCO. It is probable that COOH radicals are also present to a certain extent. A mechanism for the formation of HCO during the adsorption of formic acid on platinum has been proposed.

A study of the oxidation of adsorbed films formed on platinized platinum in methanol,formic acid and carbon dioxide solutions

The oxidation of films formed on platinized platinum in methanol, formic acid and carbon dioxide solutions has been studied. It is shown that approximately one site is bared for every electron involved in the oxidation of these films. It is concluded that the same species is absorbed in all the cases studied and that it has the composition HCO. It is probable that COOH radicals are also present to a certain extent. A mechanism for the formation of HCO during the adsorption of formic acid on platinum has been proposed.

Electron spin resonance and torsional motion of the β protons of the HOOC—CH2—C(OH)—COOH radical

The e.s.r. spectrum of the free radical HOOC—CH2—Ċ(OH)COOH formed by γ-ray irradiation of single crystals of ammonium malate monohydrate has been recorded at different temperatures. The change in the β proton coupling constants with the temperature is discussed in terms of a torsional motion about the Cα—Cβ single bond. The C13 splitting and the hydroxyl proton splitting are correlated to the conformation of the hydroxylic group, which results to be about 20° out of the radical plane. The temperature dependence of the coupling constant is consistent with the presence of strong intermolecular forces which hinder the motion. They probably arise from hydrogen bonds in the solid state.

Restricted Motion of β Protons of the HOOC–CH2–CH–COOH Radical Trapped in Urea Crystals

The ESR spectrum of the HOOC–CH2–CH–COOH radical, formed by γ-ray irradiation of a mixed crystal of urea—fumaric acid, was recorded at different temperatures. Analysis of the spectra shows that the radical undergoes some restricted torsion about the Cα–Cβ bond. A value of ∼2 kcal/mole was found for the energy barrier opposing this motion.

THE PHOTOLYSIS OF WATER VAPOR AND REACTIONS OF HYDROXYL RADICALS

The photolysis of water vapor at 1849 Å has been investigated as a possible source of hydroxyl radicals for kinetic studies. At temperatures from 23 to 350 °C and pressures from 1.3 to 28 mm, H2 and H2O2 were the only detectable products. Experiments with added oxygen indicated that O2 may have been present as an intermediate at a very low steady-state concentration, although this is not certain. Possible mechanisms are discussed.At temperatures from 200 to 350 °C, carbon monoxide appeared to react quantitatively with the hydroxyl radicals produced in the photolysis of water by the reaction, [Formula: see text] Rates of this reaction relative to those of the reactions, [Formula: see text] and [Formula: see text] were estimated from the decrement in the yield of CO2 when H2 or D2 was added to the H2O–CO system, and the following Arrhenius parameters were obtained:[Formula: see text]At temperatures below 200 °C, hydroxyl radicals were not completely converted to CO2, as the yield of CO2 increased to a maximum, then decreased again, with increasing pressure of CO. The mechanism of this system is complex, but probably involves secondary reactions of HCO or COOH radicals.

Studies on Fungicides (III) : Synthesis and Antimicrobial Activity of 4-Thiocyano Carbanilide Derivatives.

The influences of introduction of Cl, NO2, COOH and SCN radicals to 4-thiocyanocarbanilide on the germination inhibitory activity of conidio spore of Cochlibolus miyabeanus, Alternaria kikuchiana and bacteriostatic action against Staphylococcus aureus, Escherichia Coli and Bacterium oryzae were investigated. 4'-NO2 introducing compounds have the germination inhibitory activity and bacteriostatic action to the gram-negative bacteria, while 4'-SCN introducing compounds decrease the above effects. 4'-Cl introducing compound especially has a strong activity to Staphylococcus aureus. Further, 3, 5, 3', 4'and 5'-substituted compounds have 1-500 times stronger activity without exception than those substituting in 2, 6, 2', 6'-position. Both 3, 5, 4'-trichloro-4-thiocyanocarbanilide and 3, 4'-dichloro-4-thiocyanocarbanilide especially exhibit growth inhibitory activity towards Staphylococcus aureus in more than 30 million times dilution.

THE PHOTOLYSIS OF TRIFLUOROACETIC ACID VAPOR

The photolysis of CF3COOH vapor has been studied at temperatures between about 90 and 190 °C, using light of wavelengths between 2000 and 2200 Å. The major products were CO2 and C2F6, with smaller amounts of CO, H2, and CF3H. A marked reduction in the yields of CO2, CO, and H2 with increasing pressure of added isobutane or 1-butene has been interpreted to imply the presence of free COOH radicals in the system, which is supported by the tentative identification of formic and oxalic acids as products of the photolysis. It is thought that the reaction[Formula: see text]represents the main primary photolytic process, with the minor processes[Formula: see text]and[Formula: see text]accounting for no more than 27 and 7% respectively of the total at 165 °C.Some tentative conclusions have been drawn about the reactions of COOH radicals. In the present system, the disproportionation reaction,[Formula: see text]appears to predominate, with the decomposition reaction,[Formula: see text]apparently of minor importance at 165 °C.

Action of ?-rays on aqueous solutions of carbon monoxide

Solutions of CO (4.84 x 10/sup -4/ M) in 0.1 N H/sub 2/SO/sub 4/ (oxygenfree) were irradiated with gamma rays ( approximates 30,000 rad/h) and found to give H with G = 0.95, CO/sub 2/ G = 2.6, formaldehyde G = 0.5, glyoxal G = 0.3, and formic acid G = 0.4. Hydrogen peroxid could not be detected. The results are interpreted in term of a mechanism involving CHO and COOH radicals, some of the products being secondary. The effect of variations in acidity were investigated, a striking observation being that formic acid is produced with G = 44 in alkaline solution. In the presence of ferrous ions (2 x 10/sup -1/ 2 x 10/ sup -9/ M Fe/sup 2+/ 0.1 N H/sub 2/SO/sub 4/ no ferric was produced, but in the presence of ferric ions (2 x 10/sup -4/ 1 x 10/sup -9/ M Fe/sup 3+/, 0.1 N H/sub 2/SO/sub 4/) ferrous ions are produced with G = 8.3--8.4. The ratio of the rate constants for the reactions H + HCHO to H + CO ( in 0.1 N H/sub 2/ SO/sup 4/ is 14.8 plus or minus 3, of OH + CO to OH + Fe/sup 21/ (inmore » 0.1 N H/sub 2/SO/sub 4/ ) is 8.8 plus or minus 0.5, and of H + CO to H + H/sup +/ + Fe/sup 21/ (in 0.1 N H/sub 2/SO /sub 4/ is 2.2 plus or minus 0.3, all at 23 deg C. (auth)« less

Pathochemical studies on watermelon wilt. (Part 12)

In the present paper, the writer deals with the experimental evidence on the cause of so-called “vascular browning”, which is induced in the watermelon tissues infected by Fusarium oxysporum f. niveum.Microchemical observations on the injured tissues showed that, in the early stage of the disease development, the discoloration was limited to xylem parenchyma, wherein remarkable increase of phenolic substance and abnormal activation of phenoloxidase were noticeable, and was severely on progress in advance of the invading hyphae into cells, that the browning of cells seemed not to play an important role for a chemical barrier to invading hyphae, since the growth of mycelium in the browned cells was also recognized in the later stages of the disease development.Salicylic acid and another phenolic substance were isolated from watermelon roots as a vascular browning precursor. And the qualitative and quantitative changes of the precursors in the tissues during the infection process were assayed by using spectrophotometer and paper electrophoresis (Figs. 4 and 5).Fungal pectic enzyme, being functional in producing cell maceration, and fusaric acid that is toxic to the cell, might be indirectly responsible for the browning in vivo.Effects of salicylic acid and the related compounds on the growth of the causal fungus were investigated. From the results, it was shown that the antibiotic action of salicylic acid was dependent on the COOH radical rather than the OH.