ホスフィン酸

製造方法Hypophosphorous acid may be prepared by various methods: 1. Boiling white phosphorus with calcium hydroxide: P4 + 4Ca(OH)2 + 8H2O → 4Ca(H2PO2)2 + 4H2 The calcium salt is soluble in water. Treatment with sulfuric acid yields thehypophosphorous acid: (H2PO2)2Ca + H2SO4 → 2H3PO2 + CaSO4 The product mixture is filtered to remove insoluble CaSO4. The aqueous solu-tion of hypophosphorous acid is concentrated under reduced pressure.Concentrated baryta water may be used instead of calcium hydroxide.2. By treating sodium hypophosphite, NaH2PO2with an ion-exchange resin.The sodium salt may be produced by boiling white phosphorus with a solutionof sodium hydroxide, a reaction similar to (1) above. PH3 + 2I2 + 2H2O → H3PO2 + 4HI The above method may be considered safer than that involving heating whitephosphorus with an alkali. Hypophosphorous acid must be stored below 50°C. It is sold commerciallyas an aqueous solution at various concentrations.

Hypophosphorous acid is formed by reaction of barium hypophosphite and sulfuric acid, and filtering off barium sulfate. By evaporation of the solution in vacuum at 80 °C, and then cooling to 0°C, hypophosphorous acid crystallizes.

純化方法Phosphorous acid is a common contaminant of commercial 50% hypophosphorous acid. Jenkins and Jones [J Am Chem Soc 74 1353 1952] purified this material by evaporating about 600mL in a 1L flask at 40o, under reduced pressure (in N2), to a volume of about 300mL. After the solution was cooled, it was transferred to a wide-mouthed Erlenmeyer flask which was stoppered and left in a Dry-ice/acetone bath for several hours to freeze (if necessary, with scratching of the wall). When the flask was then left at ca 5o for 12hours, about 30-40% of it liquefied, and was again filtered. This process was repeated, then the solid was stored over Mg(ClO4)2 in a vacuum desiccator in the cold. Subsequent crystallisations from n-butanol by dissolving it at room temperature and then cooling in an ice-salt bath at -20o did not appear to purify it further. The free acid forms deliquescent crystals m 26.5o and is soluble in H2O and EtOH. The NaH2PO2 salt can be purified through an anion exchange resin [Klement Z Anorg Allgem Chem 260 267 1949.]