Sodium hypophosphite

Sodium hypophosphite (NaPO2H2, also known as sodium phosphinate) is the sodium salt of hypophosphorous acid and is often encountered as the monohydrate, NaPO2H2·H2O. It is a solid at room temperature, appearing as odorless white crystals. It is soluble in water, and easily absorbs moisture from the air.

Sodium hypophosphite
One sodium cation and one hypophosphite anion
Ball-and-stick model of the component ions
Names
IUPAC name
Sodium phosphinate
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.028.791
RTECS number
  • SZ5640000 (monohydrate)
UNII
  • InChI=1S/Na.H3O2P/c;1-3-2/h;3H2,(H,1,2)/q+1;/p-1 ☒N
    Key: SIGUVTURIMRFDD-UHFFFAOYSA-M ☒N
  • InChI=1/Na.H3O2P/c;1-3-2/h;3H2,(H,1,2)/q+1;/p-1
    Key: SIGUVTURIMRFDD-REWHXWOFAI
  • [O-][PH2]=O.[Na+]
Properties
NaPO2H2
Molar mass 87.98 g/mol (anhydrous)
105.99 g/mol (monohydrate)
Appearance white solid
Density 0.8 g/cm3 (monohydrate)
Melting point 310 °C (590 °F; 583 K) (monohydrate)
soluble
Solubility Ethanol, Acetic acid, Ethylene glycol, Propylene glycol[1]
Hazards
Flash point Non-flammable
Related compounds
Other anions
 Sodium phosphite
Monosodium phosphate
Disodium phosphate
Trisodium phosphate
Other cations
 Potassium hypophosphite
Related compounds
 Hypophosphorous acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Sodium hypophosphite should be kept in a cool, dry place, isolated from oxidizing materials. It decomposes into phosphine which is irritating to the respiratory tract and disodium phosphate.

2 NaH2PO2 → PH3 + Na2HPO4

Uses

Like other hypophosphites, sodium hypophosphite can reduce metal ions back into base metal. This forms the basis for electroless nickel plating (Ni-P), which is its main industrial application.[2] With this method, a durable nickel-phosphorus film can coat objects with irregular surfaces, such as in avionics, aviation and the petroleum field.

Sodium hypophosphite is capable of reducing nickel ions in solution to metallic nickel on metal substrates as well as on plastic substrates.[3] The latter requires that the substrate is activated with fine particles of palladium. The resulting nickel deposit contains up to 15% phosphorus.

It has been investigated as a food additive.

DEA List I status

The United States Drug Enforcement Administration designated sodium hypophosphite as a List I chemical under 21 CFR 1310.02 effective November 17, 2001, specifically mentioning the compound together with several other salts of hypophosphorous acid.[4][5]

References
  1. Guyon, Carole; Métay, Estelle; Popowycz, Florence; Lemaire, Marc (2015). "Synthetic applications of hypophosphite derivatives in reduction". Organic & Biomolecular Chemistry. 13 (29): 7879–7906. doi:10.1039/C5OB01032B. PMID 26083977.
  2. Abrantes, L. M. (1994). "On the Mechanism of Electroless Ni-P Plating". Journal of the Electrochemical Society. 141 (9): 2356–2360. Bibcode:1994JElS..141.2356A. doi:10.1149/1.2055125.
  3. D. Rich & M. Smith, Electroless Deposition of Nickel, Cobalt and Iron, IBM Corp (1971)
  4. 66 FR 52670—52675. 17 October 2001.
  5. 37 CFR 1310.02
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