Nitroxide Spin Adducts Research Articles

Spin adducts formed from nitroso spin traps and dithionite

In aqueous solutions of sodium dithionite, nitroso spin traps form stable nitroxide spin adducts RN(O·)SO3– as proven by their 17O hyperfine structure, rather than sulphur dioxide anion radical adducts, RN(O·)SO2–, as has been reported.

Spin-trapping of ligated boryl radicals

Amine- and phosphine-boryl radicals add to 2-methyl-2-nitrosopropane, 2,4,6-tri-t-butylnitrosobenzene, and phenyl-N-t-butylnitrone to give nitroxide spin-adducts and the application of these spin-trapping reactions as mechanistic probes is described.

A Study of the Nitroso Spin Adducts of the Pentacarbonyl Rhenium Radical

AbstractNitrosobenzene (NB) and nitroso‐tetr‐butane (NtB) were used to trap the photogenerated rhenium pentacarbonyl radical. Self trapped radicals and spin adducts were studied in detail by EPR spectroscopy. In methylene chloride, both nitroxide and anilino spin adducts can be observed with NtB at −30°. In contrast, only the nitroxide spin adduct of nitrosobenzene was observed in either hexane, or methylene chloride solution. This solvent controlled spin adduct chemistry, can be explained in terms of the solute‐solvent interaction.

The haemolytic reactions of 1-acetyl-2-phenylhydrazine and hydrazine: A spin trapping study

Free radical production from the reaction of hydrazine and 1-acetyl-2-phenylhydrazine (AcPhHZ) with oxyhaemoglobin and with human red blood cells, has been observed by the electron spin resonance technique of spin trapping. Using the spin trap 5,5-dimethyl-1-pyrroline- N-oxide (DMPO), the free radical intermediates detected depended on the hydrazine derivative, oxyhaemoglobin and the oxyhaem/hydrazine derivative concentration ratio. The reaction of hydrazine with oxyhaemoglobin in the presence of DMPO gave a nitroxide which was identified as a reduced dimer of DMPO. Whereas hydrazine-treated red blood cells, in the presence of DMPO, gave a nitroxide spin adduct which was identified as the hydroxyl radical spin adduct of DMPO, 5,5-dimethyl-1-pyrrolidino-1-oxyl (DMPO-OH). The reaction of AcPhHZ with oxyhaemoglobin, in the presence of DMPO, gave DMPO-OH, the phenyl radical spin adduct of DMPO, 5,5-dimethyl-2-phenylpyrrolidino-1-oxyl (DMPO-Ph) and an oxidised derivative of DMPO, 5,5-dimethyl-2-pyrrolidone-1-oxyl (DMPOX). The amounts of DMPO-Ph, DMPO-OH and DMPOX observed depended on the 1-acetyl-2-phenyl-hydrazine/oxyhaemoglobin concentration ratio; DMPOX replaced DMPO-OH as the concentration of AcPhHZ was decreased. DMPOX production has been previously associated with the production of highly oxidised haem iron-oxygen intermediates. AcPhHZ treated red blood cells gave DMPO-Ph and DMPO-OH spin adducts in the presence of DMPO. DMPO had little to no effect on the rate of oxygen consumption by oxyhaemoglobin with hydrazine and AcPhHZ. Moreover, the rate of oxyhaemoglobin oxidation induced by hydrazine, was not decreased by DMPO whereas the rate of oxyhaemoglobin oxidation induced by AcPhHZ was decreased approx. 40% by DMPO. DMPO (10 mM) gave a small decrease in haemolysis and lipid peroxidation induced by 1 mM hydrazine and AcPhHZ in a 1% suspension of red blood cells.

22] Spin trapping

The method of detecting reactive short-lived free radicals by the spin-trapping technique was first demonstrated in the late 1960s. At this time, the spin-trapping method involves the addition of an organic compound (spin trap) to the solution under investigation. The spin trap is capable of rapidly trapping free radicals to form more persistent radicals (spin adducts) detectable by electron spin resonance (ESR). The most commonly used spin traps are nitrones and nitroso compounds that usually give nitroxide spin adducts. An immediate requirement of the technique is that the spin trap and spin adducts are soluble in the medium of interest and that free diffusion of the spin trap to the location of the free radical event is allowed. The environment should permit high mobility of the spin adduct so that the ESR spectrum consists of a pattern of sharp lines. The detection of the ESR spectrum of a nitroxide spin adduct is proof that a radical has been trapped in the solution under investigation. Spin trapping is a kinetic method––that is, the success of the spin trapping experiment depends critically on the rate conditions that exist in the system.

Spin trapping of carboxylic esters γ-irradiated in solid and liquid phases

The radicals formed in the liquid and solid state radiolysis of esters of acetic acid CH 3-COOR ( R =-CH 3, -CH 2-CH 3, -CH(CH 3) 2, -C(CH 3) 3) were investigated by the spin trapping technique using 2,4,6-tri- t-butylnitrosobenzene. After irradiation in the solid phase ( - 196°C), the nitroxide spin-adducts of the following radicals could be identified: H·, ·CH 2-COOR, CH 3-COOR·, R = alkyl. Radiolysis in the liquid state (-78°C) resulted in the nitroxide spin-adducts of alkoxy radicals. Furthermore, anilino-type spin-adducts were detected. Based on these results a mechanism for the primary reactions in the radiolysis of these esters is proposed.