Nitrosodisulphonate, potassium

DPPH- has an intense absorption maximum around 520 run (Yordanov and Christova, 1997), and antioxidant capacity and activity measured by the reduction of DPPH- are easily quantified by VIS-spectroscopy (Brand-Williams et al, 1995 Bondet et al, 1997, Espin et al, 2000). The stable radicals Fremy s salt (potassium nitrosodisulphonate) and galvinoxyl (2,6-di-tert-butyl-a-(3,5-di-tert-butyl-4-oxo-2,5-cyclohexadien-l-ylidene)-p-tolyloxy radical) have been used in a similar manner but with ESR detection, which can be used with samples that are not optically transparent (Gardner et al, 1998). 

Hydroxylamine-trisulphonic Acid.7—The potassium salt of this acid is formed by the interaction of potassium hydrogen sulphite and potassium nitrosodisulphonate, according to the equation ... 

The classical and the most useful laboratory method for the preparation of quinones is the oxidation of monohydric phenols with the radical reagent, potassium nitrosodisulphonate [(K03S)2NO] (Fremy s salt) (the Teuber reaction).5 Details for the conversion of 3,4-dimethylphenol into 3,4-dimethyl-1,2-benzoquinone may be regarded as typical55 the probable mechanistic pathway is formulated below. 

Of the six biphenylenequinones which are possible only the 2,3-quinone has a structure in which all the formal double bonds arc exocyclic to the four-merabered ring. It has been prepared either by oxidation of 2-amino-3-hydroxybiphenylene with chromic acid or of 2-hydroxybiphenylene with potassium nitrosodisulphonate [160] ... 

More recently the oxidation of tyrosine methyl ester with potassium nitrosodisulphonate (Fremy s salt), was shown to give 2-carbomethoxy-5,6-dihydroxyindole, via the intermediate formation of dopachrome methyl ester [81a]. It was also shown that tyrosine containing peptides are oxidised by Fremy s salt in a similar manner to that previously described for their enzymatic oxidation [cf. 29]. 

Mattocks, A. R. A Simple Preparation of Dehydroretronecine using Potassium Nitrosodisulphonate. Chem. Ind. (London) 1981, 251. 

Nitroxides, such as 2,2,6,6-tetramethylpiperidine-l-o q l (TEMPO) and its various derivatives, like 4-hydro)q -2,2,6,6-tetramethylpiperidine-l-oxyl (TEMPOL), 4-amino-2,2,6,6-tetramethylpiperidine-l-0 q l (TEMPAMINE), 4-oxo-2,2,6,6-tetramethylpiperidine-l-o q l (TEMPONE), 2,2,6,6-tetra-methyl-4-trimethylammoniumpiperidine-l-o q l (CAT-1, cf. Fig. 3) etc. as well as potassium nitrosodisulphonate (Fremy s salt) are widely used as probes in investigations of ILs. 

Nitrosodisulphonic acid decomposes spontaneously into sulphuric acid, sulphur dioxide and nitric oxide. Its solution is rapidly decolorised on shaking with air or on mixing with hydrogen peroxide, per-mono- or perdi-sulphuric acid, nitric acid, chlorine or potassium chlorate. Most metallic oxides and carbonates decompose the solution, being converted into sulphates.7... 

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