Frémy's salt

Frémy's salt is a chemical compound with the formula (K4[ON(SO3)2]2), sometimes written as (K2[NO(SO3)2]). It a bright yellowish-brown solid, but its aqueous solutions are bright violet.[1][2] The related sodium salt, disodium nitrosodisulfonate (NDS, Na2ON(SO3)2, CAS 29554-37-8) is also referred to as Frémy's salt.[3]

Frémy's salt
Names
IUPAC name
Potassium nitrosodisulfonate
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.034.729
EC Number
  • 238-219-0
UNII
  • InChI=1S/2K.H2NO7S2/c;;2-1(9(3,4)5)10(6,7)8/h;;(H,3,4,5)(H,6,7,8)/q2*+1;/p-2
    Key: IHSLHAZEJBXKMN-UHFFFAOYSA-L
  • N([O])(S(=O)(=O)[O-])S(=O)(=O)[O-].[K+].[K+]
Properties
K2NO(SO3)2
Molar mass 268.33 g/mol (potassium salt)
Hazards
GHS labelling:
GHS02: FlammableGHS07: Exclamation mark
Danger
H260, H302, H312, H332
P223, P231+P232, P280, P301+P312, P302+P352+P312, P304+P340+P312
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Regardless of the cations, the salts are distinctive because aqueous solutions contain the radical [ON(SO3)2]2−.

Applications

Frémy's salt, being a long-lived free radical, is used as a standard in electron paramagnetic resonance (EPR) spectroscopy, e.g. for quantitation of radicals. Its intense EPR spectrum is dominated by three lines of equal intensity with a spacing of about 13 G (1.3 mT).[4][5][6]

The inorganic aminoxyl group is a persistent radical, akin to TEMPO.

It has been used in some oxidation reactions, such as for oxidation of some anilines and phenols[7][8][9][10][11] allowing polymerization and cross-linking of peptides and peptide-based hydrogels.[12][13]

It can also be used as a model for peroxyl radicals in studies that examine the antioxidant mechanism of action in a wide range of natural products.[14]

Preparation

Frémy's salt is prepared from hydroxylaminedisulfonic acid. Oxidation of the conjugate base gives the purple dianion:

HON(SO3H)2 → [HON(SO3)2]2− + 2 H+
2 [HON(SO3)2]2− + PbO2 → 2 [ON(SO3)2]2− + PbO + H2O

The synthesis can be performed by combining nitrite and bisulfite to give the hydroxylaminedisulfonate. Oxidation is typically conducted at low-temperature, either chemically or by electrolysis.[3][2]

Other reactions:

HNO2 + 2 HSO−
3 → HON(SO
3)2−
2 + H2O
3 HON(SO
3)2−
2 + MnO−
4 + H+ → 3 ON(SO
3)2−
2 + MnO2 + 2 H2O
2 ON(SO
3)2−
2 + 4 K+ → K4[ON(SO3)2]2

History

Frémy's salt was discovered in 1845 by Edmond Frémy (1814–1894).[15] Its use in organic synthesis was popularized by Hans Teuber, such that an oxidation using this salt is called the Teuber reaction.[9][10]

References
  1. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  2. "Synthesis and Characterization of Potassium Nitrosodisulfonate, Frémy's Salt" (PDF). tripod.com.
  3. Wehrli PA, Pigott F (1972). "Oxidation with the nitrosodisulfonate radical. I. Preparation and use of sodium nitrosodisulfonate: trimethyl-p-benzoquinone". Organic Syntheses. 52: 83. doi:10.15227/orgsyn.052.0083.
  4. Wertz JE, Bolton JR (1972). Electron Spin Resonance: Elementary Theory and Practical Applications. New York: McGraw-Hill. ISBN 978-0-07-069454-5. See page 463 for information on intensity measurements and page 86 for an EPR spectrum of Frémy's salt.
  5. Colacicchi S, Carnicelli V, Gualtieri G, Di Giulio A (2000). "EPR study of Frémy's salt nitroxide reduction by ascorbic acid; influence of bulk pH values". Res. Chem. Intermed. 26 (9): 885–896. doi:10.1163/156856700X00372. S2CID 98775951.
  6. Zielonka J, Zhao H, Xu Y, Kalyanaraman B (October 2005). "Mechanistic similarities between oxidation of hydroethidine by Frémy's salt and superoxide: stopped-flow optical and EPR studies". Free Radical Biology & Medicine. 39 (7): 853–863. doi:10.1016/j.freeradbiomed.2005.05.001. PMID 16140206.
  7. Zimmer H, Lankin DC, Horgan SW (1971). "Oxidations with potassium nitrosodisulfonate (Frémy's radical). Teuber reaction". Chemical Reviews. 71 (2): 229–246. doi:10.1021/cr60270a005.
  8. Islam I, Skibo EB, Dorr RT, Alberts DS (October 1991). "Structure-activity studies of antitumor agents based on pyrrolo[1,2-a]benzimidazoles: new reductive alkylating DNA cleaving agents". Journal of Medicinal Chemistry. 34 (10): 2954–2961. doi:10.1021/jm00114a003. PMID 1920349.
  9. Teuber HJ, Benz S (1967). "Reaktionen mit Nitrosodisulfonat, XXXVI. Chinolin-chinone-(5.6) aus 5-Hydroxy-chinolinen". Chem. Ber. (in German). 100 (9): 2918–2929. doi:10.1002/cber.19671000916.
  10. Teuber HJ (1972). "Use of Dipotassium Nitrosodisulfonate (Frémy's Salt): 4,5-Dimethyl-o-Benzoquinone". Org. Synth. 52: 88. doi:10.15227/orgsyn.052.0088.
  11. Xue W, Warshawsky D, Rance M, Jayasimhulu K (2002). "A metabolic activation mechanism of 7H-dibenzo[c,g]carbozole via o-quinone. Part 1: synthesis of 7H-dibenzo[c,g]carbozole-3,4-dione and reactions with nucleophiles". Polycyclic Aromatic Compounds. 22 (3–4): 295–300. doi:10.1080/10406630290026957. S2CID 95507636.
  12. Wilchek M, Miron T (March 2015). "Mussel-inspired new approach for polymerization and cross-linking of peptides and proteins containing tyrosines by Frémy's salt oxidation". Bioconjugate Chemistry. 26 (3): 502–510. doi:10.1021/bc5006152. PMID 25692389.
  13. Fichman G, Schneider JP (2021). "Utilizing Frémy's Salt to Increase the Mechanical Rigidity of Supramolecular Peptide-Based Gel Networks". Frontiers in Bioengineering and Biotechnology. 8: 594258. doi:10.3389/fbioe.2020.594258. PMC 7813677. PMID 33469530.
  14. Liu ZL, Han ZX, Chen P, Liu YC (November 1990). "Stopped-flow ESR study on the reactivity of vitamin E, vitamin C and its lipophilic derivatives towards Frémy's salt in micellar systems". Chemistry and Physics of Lipids. 56 (1): 73–80. doi:10.1016/0009-3084(90)90090-E. PMID 1965427.
  15. See:

Further reading
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