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Orthophosphorous acid, also known as phosphorous acid, is a moderately strong inorganic acid.
Orthophosphorous acid, or phosphorous acid, is a diprotic phosphorus oxoacid that exists as two tautomers while in solution.
Orthophosphorous acid is an intermediate in the preparation of other phosphorus compounds.
CAS Number: 13598-36-2
EC Number: 237-066-7
Molecular formula: H3O3P
Molar mass: 81.99 g/mol
Synonyms: Phosphonic acid, Phosphorous acid, Dihydroxyphosphine oxide, Dihydroxy(oxo)-λ5-phosphane, Dihydroxy-λ5-phosphanone, Orthophosphorous acid, Oxo-λ5-phosphanediol, Oxo-λ5-phosphonous acid, Metaphosphoroic acid
Orthophosphorous acid is the compound described by the formula H3PO3.
Orthophosphorous acid is diprotic (readily ionizes two protons), not triprotic as might be suggested by this formula.
Orthophosphorous acid is an intermediate in the preparation of other phosphorus compounds.
Organic derivatives of Orthophosphorous acid, compounds with the formula RPO3H2, are called Orthophosphorous acids.
The most important use of Orthophosphorous acid is the production of basic lead phosphite, which is a stabilizer in PVC and related chlorinated polymers.
Ferrous materials, including steel, may be somewhat protected by promoting oxidation ("rust") and then converting the oxidation to a metalophosphate by using phosphoric acid and further protected by surface coating.
Orthophosphorous acid, also known as phosphorous acid, is a moderately strong inorganic acid.
Orthophosphorous acid, or phosphorous acid, is a diprotic phosphorus oxoacid that exists as two tautomers while in solution.
Orthophosphorous acid is a pyridinyl biphosphonate bone resorption inhibitor.
Orthophosphorous acid which is also called Orthophosphorous acid is a colourless oxyacids of phosphorus.
Orthophosphorous acid is produced in the form of a white volatile powder by the slow combustion of phosphorus.
Orthophosphorous acid's salts are called phosphates.
Orthophosphorous acid is conveniently prepared by allowing phosphorous trichloride to react with water.
Uses of Orthophosphorous acid:
Orthophosphorous acid is used in the production of basic lead phosphonate PVC stabilizer, aminomethylene Orthophosphorous acid and hydroxyethane diOrthophosphorous acid.
Orthophosphorous acid is used as a strong reducing agent.
Orthophosphorous acid is used in the production of raw materials of phosphorous acid, synthetic fibres and organophosphorus pesticides etc.
Orthophosphorous acid is used in the production of high efficient water treatment agent amino trimethylene Orthophosphorous acid.
Orthophosphorous acid's industrial applications include use in the production of basic lead phosphite and controlling plant diseases.
The most important use of Orthophosphorous acid is the production of phosphites (phosphonates) which are used in water treatment.
Phosphites have shown effectiveness in controlling a variety of plant diseases, in particular, treatment using either trunk injection or foliar containing phosphorous acid salts is indicated in response to infections by phytophthora and pythium-type plant pathogens (both within class oomycetes, known as water molds), such as dieback/root rot and downy mildew.
Orthophosphorous acid is also used for preparing phosphite salts, such as potassium phosphite.
These salts, as well as aqueous solutions of pure Orthophosphorous acid, are fungicides.
Orthophosphorous acid is used primarily for the production of phosphonates and phosphate salts.
These derivatives are used in a number of antimicrobial applications.
In industrial synthesis PCl3 is sprayed into steam at 190oC the heat of reaction is used to distill off the hydrogen chloride and excess water vapour.
Orthophosphorous acid is used as a reagent in the synthesis of Risedronic Acid Sodium Salt.
Orthophosphorous acid is used in the production of basic lead phosphonate PVC stabilizer, aminomethylene Orthophosphorous acid and hydroxyethane diOrthophosphorous acid.
Orthophosphorous acid is also used as a strong reducing agent and in the production of phosphorous acid, synthetic fibres, organophosphorus pesticides, and the highly efficient water treatment agent ATMP.
Chemical Properties Of Orthophosphorous acid:
Orthophosphorous acid has strong reducing properties it tends to be converted to phosphoric acid.
On being heated dry Orthophosphorous acid disproportionates to give phosphine and phosphoric acid.
H3PO3 + 3H3PO3 → PH3 + 3H3PO4
Orthophosphorous acid reacts with a base like sodium hydroxide forms sodium phosphate and water.
H3PO3 + 3NaOH → Na3PO3 + 3H2O
Nomenclature And Tautomerism Of Orthophosphorous acid:
Solid HP(O)(OH)2 has tetrahedral geometry about the central phosphorus atom, with a P–H bond of 132 pm, one P=O double bond of 148 pm and two longer P–OH single bonds of 154 pm.
In common with other phosphorus oxides with P-H bonds (e.g.hypophosphorous acid and dialkyl phosphites), Orthophosphorous acid exists in equilibrium with an extremely minor tautomer P(OH)3. (In contrast, arsenous acid's major tautomer is the trihydroxy form.)
IUPAC recommends that P(OH)3 be called Orthophosphorous acid, whereas the dihydroxy form HP(O)(OH)2 is called Orthophosphorous acid.
Only the reduced phosphorus compounds are spelled with an "ous" ending.
PIII(OH)3 ⇌ HPV(O)(OH)2 K = 1010.3 (25°C, aqueous)
Preparation Of Orthophosphorous acid:
On an industrial scale, the acid is prepared by hydrolysis of phosphorus trichloride with water or steam:
PCl3 + 3 H2O → HPO(OH)2 + 3 HCl
HPO(OH)2 could be produced by the hydrolysis of phosphorus trioxide:
P4O6 + 6 H2O → 4 HPO(OH)2
Reactions Of Orthophosphorous acid:
Acid–base properties:
Phosphorous acid has a pKa in the range 1.26–1.3.
HP(O)(OH)2 → HP(O)2(OH)− + H+ pKa = 1.3
Orthophosphorous acid is a diprotic acid, the hydrogenphosphite ion, HP(O)2(OH)− is a weak acid:
HP(O)2(OH)− → HPO2−3 + H+ pKa = 6.7
The conjugate base HP(O)2(OH)− is called hydrogen phosphite, and the second conjugate base, HPO2−3, is the phosphite ion.
(Note that the IUPAC recommendations are hydrogen phosphonate and phosphonate respectively).
The hydrogen atom bonded directly to the phosphorus atom is not readily ionizable.
Chemistry examinations often test students' appreciation of the fact that not all three hydrogen atoms are acidic under aqueous conditions, in contrast with H3PO4.
Redox Properties Of Orthophosphorous acid:
On heating at 200 °C, Orthophosphorous acid disproportionates to phosphoric acid and phosphine:
4 H3PO3 → 3 H3PO4 + PH3
This reaction is used for laboratory-scale preparations of PH3.
Orthophosphorous acid slowly oxidizes in air to phosphoric acid.
Both Orthophosphorous acid and its deprotonated forms are good reducing agents, although not necessarily quick to react.
They are oxidized to phosphoric acid or its salts.
Orthophosphorous acid reduces solutions of noble metal cations to the metals.
When Orthophosphorous acid is treated with a cold solution of mercuric chloride, a white precipitate of mercurous chloride forms:
H3PO3 + 2 HgCl2 + H2O → Hg2Cl2 + H3PO4 + 2 HCl
Mercurous chloride is reduced further by Orthophosphorous acid to mercury on heating or on standing:
H3PO3 + Hg2Cl2 + H2O → 2 Hg + H3PO4 + 2 HCl
As A Ligand, Orthophosphorous acid:
Upon treatment with metals of d6 configuration, Orthophosphorous acid is known to coordinate as the otherwise rare P(OH)3 tautomer.
Examples include Mo(CO)5(P(OH)3) and [Ru(NH3)4(H2O)(P(OH)3)]2+.
Heating a mixture of potassium tetrachloroplatinate and Orthophosphorous acid gives the luminescent salt potassium diplatinum(II) tetrakispyrophosphite:
2 K2PtCl4 + 8 H3PO3 → K4[Pt2(HO2POPO2H)4] + 8 HCl + 4 H2O
Organic Derivatives Of Orthophosphorous acid:
The IUPAC (mostly organic) name is Orthophosphorous acid.
This nomenclature is commonly reserved for substituted derivatives, that is, organic group bonded to phosphorus, not simply an ester.
For example, (CH3)PO(OH)2 is "methylOrthophosphorous acid", which may of course form "methylphosphonate" esters.
Handling And Storage Of Orthophosphorous acid:
Conditions for safe storage, including any incompatibilities:
Storage conditions:
No metal containers.
Tightly closed.
Dry.
Store under inert gas.
Air sensitive.
Stability And Reactivity Of Orthophosphorous acid:
Reactivity:
No data available
Chemical stability:
The product is chemically stable under standard ambient conditions (room temperature).
Possibility of hazardous reactions:
No data available
Conditions to avoid:
no information available
First Aid Measures of Orthophosphorous acid:
General advice:
First aiders need to protect themselves.
If inhaled:
After inhalation:
Fresh air.
Call in physician.
In case of skin contact:
Take off immediately all contaminated clothing.
Rinse skin with water/ shower.
Call a physician immediately.
In case of eye contact:
After eye contact:
Rinse out with plenty of water.
Immediately call in ophthalmologist.
Remove contact lenses.
If swallowed:
After swallowing:
Make victim drink water (two glasses at most), avoid vomiting (risk of perforation).
Call a physician immediately.
Do not attempt to neutralise.
Indication of any immediate medical attention and special treatment needed:
No data available
Fire Fighting Measures of Orthophosphorous acid:
Extinguishing media:
Unsuitable extinguishing media:
For this substance/mixture no limitations of extinguishing agents are given.
Further information:
Prevent fire extinguishing water from contaminating surface water or the ground water system.
Accidental Release Measures of Orthophosphorous acid:
Environmental precautions:
Do not let product enter drains.
Methods and materials for containment and cleaning up:
Cover drains.
Collect, bind, and pump off spills.
Observe possible material restrictions.
Take up dry.
Dispose of properly.
Clean up affected area.
Exposure Controls/personal Protection of Orthophosphorous acid:
Personal protective equipment:
Eye/face protection:
Use equipment for eye protection.
Tightly fitting safety goggles
Skin protection:
Handle with gloves.
Wash and dry hands.
Full contact:
Material: Nitrile rubber
Minimum layer thickness: 0,11 mm
Break through time: 480 min
Splash contact:
Material: Nitrile rubber
Minimum layer thickness: 0,11 mm
Break through time: 480 min
Body Protection:
protective clothing
Control of environmental exposure:
Do not let product enter drains.
Identifiers of Orthophosphorous acid:
CAS Number: 13598-36-2
EC Number: 237-066-7
MDL number: MFCD00137258
EC Name: Orthophosphorous acid
Molecular formula: H3O3P
Properties of Orthophosphorous acid:
Chemical formula: H3PO3
Molar mass: 81.99 g/mol
Appearance: white solid deliquescent
Density: 1.651 g/cm3 (21 °C)
Melting point: 73.6 °C (164.5 °F; 346.8 K)
Boiling point: 200 °C (392 °F; 473 K) (decomposes)
Solubility in water: 310 g/100 mL
Solubility: soluble in ethanol
Acidity (pKa): 1.1, 6.7
Magnetic susceptibility (χ): −42.5·10−6 cm3/mol
Odour: Sour odour
Appearance: White solid, deliquescent
Covalently-Bonded Unit: 1
Hydrogen Bond Acceptor: 3
Complexity: 8
Solubility: Soluble in water
Physical state flakes
Color: white
Odor: odorless
Melting point/freezing point:
Melting point/range: 63 - 74 °C at 1.013 hPa
Initial boiling point and boiling range: 259 °C at 1.013 hPa
Flammability (solid, gas): No data available
Upper/lower flammability or explosive limits: No data available
Flash point: Not applicable
Autoignition temperature: not auto-flammable
Decomposition temperature: No data available
pH: at 20 °C acidic
Viscosity
Viscosity, kinematic: No data available
Viscosity, dynamic: No data available
Water solubility: soluble
Partition coefficient: n-octanol/water: Not applicable for inorganic substances
Vapor pressure < 0,1 hPa at 20 °C
Density: 1,651 g/cm3 at 25 °C - lit.
Relative density No data available
Relative vapor density: No data available
Particle characteristics: No data available
Explosive properties: No data available
Oxidizing properties: The product has been shown not to be oxidizing
Other safety information: No data available
