Labelling nitrite

Oxidation of T to generate thianthrene 5-oxide occurs cleanly with nitrite and nitrate (72JOC2691). Incorporation of 0 from labeled nitrite was considered consistent with a process (arrows on 31) involving 31 as an intermediate and producing NO as byproduct. 

The labeled nitrite complex may be caused to rearrange by heating. In this process no loss of, 80 is found even in the presence of excess nitrile, confirming AdeU hypothesis that the reaction is an intramolecular rearrangement ... 

In addition to rapid exchange of thiolate ligands with R SH and for R S , the mononuclear complexes [Fe(NO)2(SR)2] also undergo (23) rapid exchange of the nitrosyl ligands in the presence of isotopically labeled nitrite a W-shaped N203 intermediate was proposed (23) [Eq. (22)]. 

Zweier et al. [69] pointed out the non-enzymic reduction of nitrite to NO in the ischaemic heart. It was shown that the acidotic nature of the ischaemic heart led to a reducing atmosphere that caused the reduction of nitrite to NO. This NO generation was independent of NOS and NOS inhibitors had only minimal effects on the NO generated. Using labelled nitrite ions they were able to demonstrate that nitrite can be reduced to NO in this model and was negatively correlated with intracellular pH and the production of NO with a threshold for NO detection at pH 6. 

Esters.—Photolysis of the 1 l/ -nitrite (671) in the c-nor-D-homo series affords the nitrone (672), through the reaction sequence illustrated. Use of N-labelled nitrite has revealed that the NO group suffers isotopic scrambling in an inter-molecular process. ... 

One proposed mechanism for CuNiR, which parallels catalysis by the well-characterized heme NiRs, involves the formation of a Cu -NO+ intermediate formed by protonation of bound nitrite followed by the abstraction of an oxygen atom to form OH . Although the Cu -NO intermediate has not been observed directly, the formation of N2O, a minor product of nitrite reduction by AfNiR, has been attributed to the reaction of a Cu nitrosyl intermediate with NO to form N2O. Consistent with this, large amounts of N20 were formed during turnover in the presence of N-labeled nitrite and N-labeled NO. 

A similar reaction with Pd(N02)2(PMePh2)2 and CO produces CO2 and the cluster compound Pd4(CO)5(PMePh2)4- Further work on this reaction using oxygen-18-labeled nitrite has confirmed this ligand to be the source of oxygen, and a cyclic intermediate is proposed for the oxygen transfer step. ... 

Oxygen exchange in doubly labeled nitrite has been successfully followed by The presence of 0 results in an up-field... 

Carbon-centered radicals thus generated then combine with nitric oxide to form nitroso compounds, which readily isomerize to afford the corresponding oximes (or nitrosodimers ). Quantum-yield studies of the overall process cited above indicated that this free radical reaction is not a chain process. The behaviors of the nitric oxide generated in the solution was studied by using labeled nitrites the photolysis of an equimolecular mixture of N nitrite A and N nitrite B gave a mixture of two products (arising from intramolecular hydrogen abstraction) in which N and N were completely scrambled... 

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