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The formation of ONOOH/ONOO- in water was investigated by applying pulse radiolysis of nitrite and nitrate solutions. The overall rate constant of the reaction of *OH with *NO2 was found to be (1.0 +/- 0.2) x 10(raised to power 10)/Ms. The reaction produces almost equal amounts of ONOOH and NO3- + H+. The overall constant of the reaction of *NO2 with O*- was found to be (3-4) x 10(raised to power 9)/Ms. The rate constants of ONOO- decomposition at pH 13 and 14 were found to be 1.3 x 10(raised to power -5) and 1.1 x 10(raised to power -5)/s, respectively, and the yield of NO2- was found to be ca. 50%.

Pulse radiolysis and stopped-flow techniques were used to investigate the compound peroxynitric acid and the mechanism of its decomposition in the presence of various substrates. Results of the study identified O2NOO-*, which has the ability to oxidize ferrocyanide and NADH, dissociates into the couple .NO2 and O2.-. The contribution of this chemical reaction to the decomposition of O2NOO- is ca.50%. Two alternative mechanisms are suggested to account for the experimental results.

A study was conducted to characterize the one-electron oxidation of benzoylthiolate through the azide radical in aqueous solution. The transient absorption spectrum of benzoylthiyl radicals were determined after electron pulse irradiation of a solution containing 5 mM PhCOS- and 0.1 m NaN3. Results indicated that the Ph radicals add to N3- to form PhN3- radical anions which disproportionate to determine PhN3 and PhNH2 as end products.

A study was conducted on CH3C(O)S. radical formation upon one electron oxidation of acetyl thiolate CCH3C(O)S- in aqueous solutions. One-electron oxidation of CH3C(O)S- ions produced CH3C(O)S. radicals. The radical subsequently underwent beta-fragmentation to form CH3. and COS with a rate constant of 6.6x104 S- at room temperature. The experimental data for the kinetics and thermochemical properties of CH3-C(O)SH and CH3C(O)S. radicals obtained in this work were then compared with those of the PhC(O)SH and PhC(O)S. radicals.

Pulse radiolysis enables the determination of the rate of one-electron oxidation of thiol groups in glutathione, homocysteine and cysteine by azide radicals. Use of an oxidant, methylviologen, helps identify the alpha-aminoalkyl radicals, which are generated from an intramolecular rearrangement of thiyl radical. Thiyl radicals abstract hydrogen from alpha-amino C-H bonds of alanine and glycine, and kinetic studies enable the determination of the rate constants of these intermolecular hydrogen abstraction. Mechanistic study suggests that the conversion of thiyl radical into alpha-amino carbon-centered radical involves an intramolecular hydrogen abstraction.

Kinetic studies of hydrogen abstraction reactions between bromine atoms and various hydrogen donors, RH, in aqueous and other media reveal that polarity of the solvent does not influence hydrogen abstraction rate. The reaction's rate-determining step involves formation of molecular HBr. The rate of hydrogen abstraction involving alcohol is higher than that involving alkanes. The mechanism for increased rate of reaction is discussed in terms of a polar transition state.

The 4-substituted aniline radical potentials and pKa values are linearly dependent on the Brown Sigma(sub p)(super +) values. The combination of one-electron reduction potentials and pKa values yield the N-H bond dissociation energies of 4-substituted anilines which are linearly dependent on the 4-substituents. The study used pulse radiolysis techniques.

A kinetic study of the chain bromination of 2-methyl-2-propanol by N-bromosuccinimide in water probes into the reactivity of the succinimidyl radical, S(rad). Rate-constant analysis of the chain-propagating steps of both the S(rad)- and Br(rad)-mediated chain reactions, under pulse- and gamma-radiolyses conditions, places the reactivity of S(rad) below that of OH(rad) in terms of H-atom abstraction, but above it in terms of electron affinity. The results provide evidence for S(rad) as a type-II radical.

The one-electron reduction potentials of 4-substituted benzoylthiolates E degree were measured in aqueous solutions by means of pulse radiolysis. The substituent effects on the redox potential, the pK(sub a), and the kinetics of the beta-fragmentation reactions were studied.

A study investigated the kinetics and mechanism of proton-coupled electron transfer (PCET) from a series of phenols to a laser flash generated [[Ru([bpy.sub.3])].sup.3+] oxidant in aqueous solution. Findings show that hydrogen bonds can promote PCET through the concerted electron transfer-deprotonation (CEP) mechanism, resulting in much higher rates than those for the corresponding reaction with the same driving force but in the absence of an internal hydrogen bond.

The one-electron oxidized product of hydroxylamine [NH(sub 2)-OH] is the aminoxyl radical (NH2O.). The (NH2O.) radical deprotonates to yield HNO(super .-) with a pKa = 12.6 (plusmn) 0.3.

A review discusses the reaction patterns of ONOOH/OONO(super -) and O2NOOH/O2NOO(super -) and demonstrates the main differences between these peroxides. A scrutinization of the behavior of derivatives of these compounds that include alkylated peroxynitrites and peroxynitrates as well as some biologically important enzyme-based metal peroxynitrates are presented.

The reaction of alkyl peroxyl radicals with (super .)NO2 and (super.)NO using the pulse radiolysis method is studied. The reactions result in comparatively long-lasting alkyl peroxynitrates that are in balance with the original radicals

Reply to the comment on the report on redox and acid-base properties of 2,2E- and 4,4E-biphenols in aqueous solutions are described.

Research has been conducted on peroxynitrous acid. The authors have investigated the kinetics of the acid's decomposition in the presence of HClO (sub)4 and at a constant ionic strength, and they report that acid's decay rate decrease in the presence of H (sub)2 O (sub)2.

Peroxyl radicals were produced by steady-state gamma-radiolysis in the presence of O3. Quantum chemical computations support a mechanism, in which formation of an alkyl trioxide radical is the rate-determining step.

In rapid nucleophilic addition equilibria with both acetaldehyde and acetone, peroxynitrite is involved, whereby tetrahedral adduct anions are formed. The adduct anions undergo protonation by water and added buffers and both the anionic and neutral adducts undergo homolysis along the weak O-O bond, the rate of constant for the process is 10 raise to 6 S (super -1).

The previous study showed that the activation parameters for the decomposition of O2NOO- were A = 1 X 10(super 12)/sec and Ea = 16.3 kcal/mol utilizing the pulse radiolysis method for generation of O2NOO-. These values were substantially smaller than A = 7.7 X 10(super 20)/SEC AND eA = 28.7 kcal/mol, which were computed by Regimbal and Mozurkewich by following the decomposition of O2NOOH as a function of pH at pH < 5.

Investigations of the outer-sphere electron transfer related to the autoxidation of closed-shell organics yielded kinetic data for a reaction of singlet organics with O2, where neither powerful orbital overlap in the transition phase nor bond development in the elementary stage is spin-allowed. This data covers a scope of 23 orders of magnitude in K12, and once the value of K12 is identified, the initiation rate of any organic autoxidation inside a factor of ca.10 can be predicted. Besides outer-sphere electron transfer, no other process can be conclusively proved to exist.

The reaction of ozone with the anion of H2O2 (peroxone process) gives rise to ∙OH radicals (Staehelin, J.; Hoign, J. Environ. Sci. Technol. 1982, 16, 676-681). Thermokinetic considerations now suggest that the electron transfer originally assumed as the first step has to be replaced by the formation of an adduct, HO2- + O3 → HO5- (ΔG° = -39.8 kJ mol-1). This decomposes into HO2∙ and O2∙- (ΔG° = 13.2 kJ mol-1). HO2∙ is in equilibrium with O2∙- + H+, and O2∙- undergoes electron transfer to O3 giving rise to further O3∙-. The decay of O3∙- into ∙OH is now discussed on the basis of the equilibria O3∙- O2 + O∙- and O∙- + H2O ∙OH + OH-, excluding HO3∙ as the intermediate originally assumed. To account for the observation of the peroxone process being only 50% efficient, the decay of HO5- into 2 O2 + OH- (ΔG° = -197 kJ mol-1) is proposed to compete with the decay into HO2∙ and O3∙-. [ABSTRACT FROM AUTHOR]

Hollow silica nanospheres were prepared by template growth of silica gel on monodisperse (100−500 nm) polystyrene beads coated with poly-l-lysine, followed by calcinations. A similar route was used to prepare titania nanospheres. [ABSTRACT FROM AUTHOR]

A versatile procedure is presented for fast and efficient micropatterning of multiple types of covalently bound surface chemistry in perfect register on and between conductive polymer microcircuits. The micropatterning principle is applied to several types of native and functionalized PEDOT (poly(3,4-ethylenedioxythiophene)) thin films. The method is based on contacting PEDOT-type thin films with a micropatterned agarose stamp containing an oxidant (aqueous hypochlorite) and applying a nonionic detergent. Where contacted, PEDOT not only loses its conductance but is entirely removed, thereby locally revealing the underlying substrate. Surface analysis showed that the substrate surface chemistry was fully exposed and not affected by the treatment. Click chemistry could thus be applied to selectively modify re-exposed alkyne and azide functional groups of functionalized polystyrene substrates. The versatility of the method is illustrated by micropatterning cell-binding RGD-functionalized PEDOT on low cell-binding PMOXA (poly(2-methyl-2-oxazoline)) to produce cell-capturing microelectrodes on a cell nonadhesive background in a few simple steps. The method should be applicable to a wide range of native and chemically functionalized conjugated polymer systems., (© 2012 American Chemical Society)

Complex one- or two-dimensional concentration gradients of alkynated molecules are produced on azidized conducting polymer substrates by stenciled "electro click chemistry". The latter describes the local electrochemical generation of catalytically active Cu(I) required to complete a "click reaction" between alkynes and azides at room temperature. A stencil on the counter electrode defines the shape and multiplicity of the gradient(s) on the conducting polymer substrate, while the specific reaction conditions control gradient steepness and the maximum concentration deposited. Biologically active ligands including cell binding peptides are patterned in gradients by this method without losing their biological function or the conductivity of the polymer.