The Cu(I) catalyzed Meerwein reaction in aqueous solutions proceeds via a radical mechanism. The effect of several ligands.

The effect of the ligands 2,5,8,11-tetramethyl-2,5,8,11-tetraaza-dodecane and fumarate on the mechanism and kinetics of the Cu(I) catalyzed Meerwein reaction was studied. The results point out that initially the Cu(I) ion binds to the aromatic ring with the diazo substituent. This reaction is followed by a redox process involving N2 loss and the formation of an aryl radical, R˙.

The effect of pyrophosphate, tripolyphosphate and ATP on the rate of the Fenton reaction.

It has been recently reported that pyrophosphate, tri-polyphosphate, ATP and analogous ligands considerably decrease the yield of hydroxyl radicals by the Fenton reaction under conditions where [H(2)O(2)]>>[Fe(II)L(n)]. It was suggested that this effect is due to the slowing down of the Fenton reaction by these ligands. This suggestion seemed surprising as polyphosphate ligands stabilize Fe(III).

On the mechanism of reduction of maleate and fumarate by Ni(I)(1,4,8,11-tetraazacyclotetradecane)+ in aqueous solutions.

Ni(I)(1,4,8,11-tetraazacyclotetradecane)(+), Ni(I)L(+), was produced in neutral aqueous solutions by radiolytic techniques. The mechanism and kinetics of the reaction of Ni(I)L(+) with maleate and fumarate were studied applying pulse-radiolysis and analysis of the final products. Surprisingly the mechanisms of reduction of maleate and fumarate differ considerably.

New mechanistic aspects of the Fenton reaction.

The kinetics of the Fenton reaction was studied in detail. A second reaction step in the presence of excess H2O2 is attributed to formation of the complex Fe(III)(-O2H)(aq). Therefore, the reaction of Fe(H2O)(6)(2+) with Fe(III)(-O2H)(aq) in the presence of Fe(II) to form Fe(III)(aq) (k=(7.

Reduction of ethylene by Ni(I)(cyclam)+ in aqueous solutions.

Ni(I)(1,4,8,11-tetraazacyclotetradecane)(+) reduces ethylene quantitatively to ethane plus butane (and hexane traces) in neutral aqueous solutions. A radical mechanism is proposed.

Mechanism of the reaction of radicals with peroxides and dimethyl sulfoxide in aqueous solution.

The reactions of methyl and methylperoxyl radicals derived from dimethyl sulfoxide (DMSO) with hydrogen peroxide, peroxymonocarbonate (HCO4 (-)), and persulfate were studied. The major reaction observed for the hydroperoxides was the abstraction of the hydrogen atom by the radicals. The radicals interact with a lone pair of electrons on the peroxide to produce methanol and formaldehyde.

Mechanism of reaction of alkyl radicals with (Ni(II)L)2+ complexes in aqueous solutions.

The reactions of methyl radicals, *CH3, with the macrocyclic complexes Ni(II)L(1-5) (L(1-5) = cyclam derivatives, vide infra) and Ni(II)edta in aqueous solutions were studied. Methyl radicals react with all these nickel complexes, forming intermediates with Ni(III)-C sigma-bonds. The L(m)Ni(III)-CH3 complexes are formed in equilibria processes with relatively fast forward rate constants of k(f) > 1 x 10(8) M(-1) s(-1) (except in the case of NiL2-trans I cyclam, where the reaction is slower).

Detection of nitric oxide from pig trachea by a fluorescence method.

A nitronyl nitroxide radical covalently linked to an organic fluorophore, pyrene, was used to detect nitric oxide (NO) from freshly excited tissues. This approach is based on the phenomenon of the intramolecular fluorescence quenching of the fluorophore fragment by the nitroxide. The pyrene-nitronyl (PN) reacts with NO to yield a pyrene-imino nitroxide radical (PI) and NO(2).