Title: Hypophosphorous Acid
CAS Registry Number: 6303-21-5
Molecular Formula: H3O2P
Molecular Weight: 66.00
Percent Composition: H 4.58%, O 48.48%, P 46.93%
Literature References: Conveniently prepd by treating NaH2PO2 with an ion-exchange resin: Klement, Z. Anorg. Allg. Chem. 260, 267 (1949). Review: Ohashi, "Lower Oxo Acids of Phosphorus and Their Salts" in Topics in Phosphorus Chemistry Vol. 1, M. Grayson, E. J. Griffith, Eds. (Interscience, New York, 1964) pp 113-187.
Properties: The water-free acid forms deliquesc crystals; supercools to a colorless, odorless, oily liquid. d 1.493. mp 26.5°. Dec by heat into H3PO4 and spontaneously flammable PH3. Miscible with water, alcohol, ether. Oxidized by hot H2SO4; SO2 and S formed. It is a powerful reducing agent. Marketed in aq solns of various concns, e.g., 50%, d 1.274; 30-32%, d 1.13; 10%, d 1.04. pK1 1.1.
Melting point: mp 26.5°
pKa: pK1 1.1.
Density: d 1.493; d 1.274; d 1.13; d 1.04