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Diprotic acid is an oxoacid of phosphorus with an oxidation number of +3, whose chemical formula is H3PO3.
Diprotic acid's molecular weight is 82.00 g/mol and its density is 1.65 g/cm3.
Diprotic acid is obtained by hydrolysis of phosphorus trichloride.
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, Phosphonic acid, Phosphorous acid, Dihydroxyphosphine oxide, Dihydroxy(oxo)-λ5-phosphane, Dihydroxy-λ5-phosphanone, Orthophosphorous acid, Oxo-λ5-phosphanediol, Oxo-λ5-phosphonous acid, Metaphosphoroic acid, Phosphonsaeure, phosphorige Saeure, trihydroxidophosphorus, Phosphorous acid, ortho, O-PHOSPHOROUS ACID, trioxophosphoric(3-) acid, H2PHO3, (HO)2HPO, HPO(OH)2, hydridodihydroxidooxidophosphorus, (PHO(OH)2), P(OH)3, trihydrogen trioxophosphate(3-), DTXCID5015511, DTXCID6029674, hydridotrioxophosphoric(2-) acid, (P(OH)3), dihydrogen hydridotrioxophosphate(2-), PHOSPHONIC ACID, PHOSPHORUS ACID, Phosphorous acid 99%, Phosphonsure, Phospohorous acid, Phosphorous Acid Crystal, AURORA KA-1076, orthophosphorus, ORTHOPHOSPHOROUS, Phosphorous acid,
Diprotic acid is the compound described by the formula H3PO3.
Diprotic acid is diprotic (readily ionizes two protons), not triprotic as might be suggested by this formula.
Diprotic acid is an intermediate in the preparation of other phosphorus compounds.
Organic derivatives of Diprotic acid, compounds with the formula RPO3H2, are called Diprotic acids.
Diprotic acid which is also called Diprotic acid is a colourless oxyacids of phosphorus.
Diprotic acid is produced in the form of a white volatile powder by the slow combustion of phosphorus.
Diprotic acid's salts are called phosphates.
Diprotic acid is conveniently prepared by allowing phosphorous trichloride to react with water.
In inorganic chemistry, Diprotic acid is a phosphorus oxoacid with a formula of H3PO3, more commonly known as phosphorous acid.
Diprotic acid exists in solution as two tautomers, the major one being HP(O)(OH)2 and the minor one P(OH)3.
The former is sometimes termed Diprotic acid, with the latter designated as phosphorous acid.
In organic chemistry, a Diprotic acid is a compound with the general formula RP(O)(OH)2.
An example of an organic Diprotic acid is Foscarnet.
An oligoDiprotic acid refers to a few molecules of Diprotic acid condensed into a molecule with the loss of water.
A general formula for such oligoDiprotic acids is (HPO)nOn-1(OH)2, where n = 2, 3, 4, etc., oligo-.
A polyDiprotic acid can have dozens of such Diprotic acid units condensed in a row with the loss of H2O for each unit added on.
An example that incorporates triDiprotic acid: ethane-1,1,2-triDiprotic acid.
In some phosphonic anhydrides (RPO2)3, R can be tBu, 2-methylphenyl, 2,4,6-trimethylphenyl
Diprotic acid is a common inorganic acid with the chemical formula H3PO4.
The appearance of Diprotic acid is colorless, transparent and syrupy liquid.
Diprotic acid is odorless, sour, easily soluble in water and ethanol, etc.
Diprotic acid appears as a white or yellow crystalline solid (melting point 70.1 deg C) or a solution of the solid.
Density of Diprotic acid is 1.651 g /cm3.
Diprotic acid is a diprotic phosphorus oxoacid that exists as two tautomers while in solution.
Diprotic acid is the compound described by the formula H3PO3.
Diprotic acid is one of the oxoacids of phosphorus, other important members being phosphoric acid (H3PO4) and hypophosphorous acid (H3PO2).
Note that only the reduced phosphorus compounds are spelled with an "ous" ending.
Other names for this acid are orthophosphorous acid and dihydroxyphosphine oxide.
HP(O)(OH)2 is Diprotic acid of the hydrolysis of its acid anhydride, P4O6: P4O6 + 6 H2O → 4 HP(O)(OH)2
An analogous relationship connects H3PO4 and P4O10.
Diprotic acid is an oxoacid of phosphorus with an oxidation number of +3, whose chemical formula is H3PO3.
Diprotic acid's molecular weight is 82.00 g/mol and Diprotic acid density is 1.65 g/cm3.
Diprotic acid is obtained by hydrolysis of phosphorus trichloride.
In solution, it shows tautomerism with Diprotic acid.
In organophosphorus chemistry, Diprotic acid is the generic name for a series of organophosphorus compounds with the general formula R-P(=O)(OH )2, where R is an organic group.
Diprotic acid, H3PO3, is diprotic (readily ionizes two protons), not triprotic as might be suggested by this formula.
Diprotic acid is as an intermediate in the preparation of other phosphorous compounds.
Because preparation and uses of “Diprotic acid” actually pertain more to the major tautomer, Diprotic acid, it is more often referred to as “phosphorous acid”.
Diprotic acid has the chemical formula H3PO3, which is best expressed as HPO(OH)2 to show Diprotic acid diprotic character.
Diprotic acid is a phosphorus oxoacid.
Diprotic acid is a conjugate acid of a dihydrogenphosphite.
Diprotic acid is a tautomer of a Diprotic acid.
Diprotic acid is deliquescent.
Diprotic acid absorbs oxygen from the air very readily to form phosphoric acid.
Diprotic acid is soluble in water.
Diprotic acid is a non flammable.
Diprotic acid is a common inorganic acid with the chemical formula H3PO4.
Diprotic acid is acids containing phosphorous.
Diprotic acid is able to release protons when in aqueous solutions.
Diprotic acid is phosphorous containing acids that have many industrial applications such as in the production of fertilizers.
Phosphoric acid is a phosphorous containing acid having the chemical formula H3PO4.
The IUPAC name of Diprotic acid is trihydroxidooxidophosphorus.
Diprotic acid is a triprotic acid because Diprotic acid can release three protons (hydrogen ions) in an aqueous medium.
The molar mass of phosphoric acid is 97.99 g/mol.
Phosphoric acid is available as a white solid that is deliquescent or as a syrupy liquid that has a high viscosity.
However, Diprotic acid odorless.
The melting point of Diprotic acid is 42.35◦C and the boiling point is 213◦C, but at high temperatures, Diprotic acid decomposes.
Diprotic acid is an acid containing phosphorous and the chemical formula is H3PO3.
Although this chemical structure contains three hydrogen atoms.
A diprotic acid is an acid that is capable of releasing two hydrogen ions (protons) to an aqueous medium.
Diprotic acid is also called orthophosphorous acid.
The molar mass of Diprotic acid is 81.99 g/mol.
At room temperature, Diprotic acid is a white solid that is deliquescent (absorb water from the air when exposed and dissolve).
The melting point of Diprotic acid is 73.6◦C and the boiling point is 200◦C.
At temperatures above the boiling point, the compounds tend to decompose.
When considering the chemical structure of the Diprotic acid, it has a phosphorous atom as the central atom bonded with two –OH groups and one oxygen atom bonded via a double bond and a hydrogen atom bonded via a single bond.
This structure is known as a Pseudo-tetrahedral structure.
The Diprotic acid is made via hydrolysis of the anhydride of the acid:
P4O6 + 6 H2O → 4 H3PO3
But in industrial scale productions,phosphorous chloride (PCl3) is hydrolyzed by steam:
PCl3 + 3 H2O → H3PO3 + 3 HCl
Diprotic acid is used as a reducing agent in chemical analysis.
This acid readily converts into phosphoric acid when heated to about 180◦C.
The salts formed by Diprotic acid are known as phosphates.
The most common application of phosphorus acid is that; Diprotic acid is used in the production of basic lead phosphite (a stabilizer in PVC).
1. Synthesis of Organic Diprotic acids:
Organic Diprotic acids (Phosphorous Acid) are derivatives in which a hydrogen atom on a phosphorus atom is replaced by an alkyl group.
The general formula is expressed as R-P(=O)(OH) 2.
Foscarnet, an antiviral drug, is an example of an organic Diprotic acid.
Examples of organic Diprotic acids (Phosphorous Acid) are CH3P (O)(OH )2 (methylDiprotic acid) and C6H5P (O)(OH )2 (phenylDiprotic acid).
The trialkyl phosphite esters spontaneously transfer the alkyl group from the oxygen atom to the phosphorus atom in an isomerization reaction, yielding the alkylDiprotic acid dialkyl ester.
P-alkylDiprotic acid diesters can be synthesized from phosphite tri-esters and alkyl halides.
This reaction is called the Michaelis-Arbuzov Reaction.
2. Reaction of Diprotic acid:
Diprotic acid is used as a raw material by taking advantage of the reactivity of the P-H bond.
They are alkylated by the Kabachnik-Fields reaction or the Pudovik reaction to yield aminophosphonates useful as chelating agents.
For example, nitrilotris(methylene Diprotic acid) can be synthesized industrially.
Alkylation of Diprotic acid by Michael addition of an acrylic acid derivative yields a Diprotic acid with a carboxy group.
Uses of Diprotic acid:
The most important use of Diprotic acid is the production of basic lead phosphite, which is a stabilizer in PVC and related chlorinated polymers.
Diprotic acid is also used in preparing PMIDA which is a very important intermediate of herbicide glyphosate.
Diprotic acid is used in the production of basic lead phosphonate PVC stabilizer, aminomethylene Diprotic acid and hydroxyethane diDiprotic acid.
Diprotic acid is also used as a strong reducing agent and in the production of Diprotic acid, synthetic fibres, organophosphorus pesticides, and the highly efficient water treatment agent ATMP.
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.
Industry: Diprotic acid is used in removing dust from the metal surfaces.
Diprotic acid is uiron,or steel tools and other surfaces that are rusted.
Diprotic acid is helpful in cleaning the mineral deposits, cement nous smears and hard water stains.
Food: Diprotic acid is used to acidify the foods and beverages such as colas.
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.
Medicine: Diprotic acid is an important ingredient in over the counter medications to combat nausea.
Diprotic acid is used in the production of basic lead phosphonate PVC stabilizer, aminomethylene Diprotic acid and hydroxyethane diDiprotic acid.
Diprotic acid is used as a strong reducing agent.
Diprotic acid is used in the production of raw materials of phosphorous acid, synthetic fibres and organophosphorus pesticides etc.
Diprotic acid is used in the production of high efficient water treatment agent amino trimethylene Diprotic acid.
Sometimes confusingly, both these names are also used to refer to H3PO3 in general, i.e. both tautomers.
Diprotic acid's industrial applications include use in the production of basic lead phosphite and controlling plant diseases.
What’s more, Diprotic acid has many important applications in food, medical, fertilizer and other industries.
So Diprotic acid can be used as food additives, dental and orthopedic surgery, rust inhibitors, electrolytes, fluxes, dispersants, industrial corrosives, fertilizer raw materials and household cleaning products.
Diprotic acid is mainly used in the manufacture of various phosphate, such as ammonium phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, etc and condensation phosphate class.
As a chemical reagent uses of Diprotic acid: Diprotic acid is used in chemical reactions as a reducing agent that is somewhat less vigorous than the related hypophosphorous acid.
Diprotic acid is a diprotic phosphorus oxoacid that exists as two tautomers in solution, with the major one being HP(O)(OH)2 and the minor one being P(OH)3.
Diprotic acid applications include use in basic lead phosphite production and controlling plant diseases.
Diprotic acid is an intermediate in the preparation of other phosphorous compounds.
Diprotic acid is a raw material to prepare phosphonates for water treatment such as iron and manganese control, scale inhibition and removal, corrosion control and chlorine stabilization.
The alkali metal salts (phosphites) of Diprotic acid are being widely marketed either as an agricultural fungicide (e.g. Downy Mildew) or as a superior source of plant phosphorous nutrition.
Diprotic acid is used in stabilizing mixtures for plastic materials.
Diprotic acid is used for inhibiting high-temperature of corrosion-prone metal surfaces and to produce lubricants and lubricant additives.
Diprotic acid is used to produce phosphonates like ATMP, HEDP, PBTC which are used as scale inhibitor or corrosion inhibitors in water treatment.
Diprotic acid is used to prepare phosphite salts which are used in controlling microbial plant diseases.
Diprotic acid has strong reducing properties and can be used as a reducing agent in electroless plating.
Silver and copper can be deposited from aqueous solutions of silver nitrate andcopper sulfate, respectively, for plating.
Diprotic acid is used to produce the fertilizer phosphate salt like potassium phosphite, ammonium phosphite and calcium phosphite.
Diprotic acid is actively involved in the preparation of phosphites like aminotris(methyleneDiprotic acid) (ATMP), 1-hydroxyethane 1,1-diDiprotic acid (HEDP) and 2-phosphonobutane-1,2,4-tricarboxylic Acid (PBTC), which find application in water treatment as a scale or corrosive inhibitor.
Diprotic acid is also used in chemical reactions as a reducing agent.
Diprotic acid's salt, lead phosphite is used as PVC stabilizer.
Diprotic acid is also used as a precursor in the preparation of phosphine and as an intermediate in the preparation of other phosphorus compounds.
Diprotic acid (additive E338) is used to acidify foods and beverages such as various colas.
Diprotic acid provides a tangy or sour taste.
Diprotic acid may be used to remove rust by direct application to rusted iron, steel tools, or other surfaces.
Diprotic acid is used in dentistry and orthodontics as an etching solution, to clean and roughen the surfaces of teeth where dental appliances or fillings will be placed.
Diprotic acid is sued as an additive to stabilize acidic aqueous solutions within a wanted and specified pH range
Diprotic acid is used as a dispersing agent in detergents and leather treatment
Diprotic acid is used as a pH adjuster in cosmetics and skin-care products
Dentistry uses:
Diprotic acid is mixed with zinc powder and forms zinc phosphate, and Diprotic acid is useful in temporary dental cement.
In orthodontics, zinc is used as an etching solution to help clean and roughen the surface of teeth.
Fertilizer uses:
Diprotic acid is used as reaction fertilizer in the soil around a granule acidification is generated that improves the utilization of phosphorus applied and available in the rhizosphere.
Due to Diprotic acid nitrogen content (present as ammonia), Diprotic acid is good for crops that require these nutrients in Diprotic acid initial phase
Conversion to phosphine uses:
Phosphine, being a flammable and toxic gas, is inconvenient to store.
Fortunately this useful species is readily prepared by thermal decomposition of Diprotic acid, which degrades at about 180°C:
4 HP(O)(OH)2 → PH3 + 3 H3PO4
Since Diprotic acid is a syrupy non-volatile liquid, the gaseous PH3 is readily separated.
In agriculture uses:
A large quantity of Diprotic acid is used as phosphatic fertilizer.
Pure Diprotic acid is also used for preparing phosphite salts, such as monopotassium phosphite or aluminum phosphonate.
These salts, as well as aqueous solutions of pure Diprotic acid, have shown effectiveness in controlling a variety of microbial plant diseases—in particular, treatment using either trunk injection or foliar sprays containing Diprotic 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.
Diprotic acid may be used as one of the reaction components for the synthesis of the following:
α-aminomethylDiprotic acids via Mannich-Type Multicomponent Reaction
1-aminoalkaneDiprotic acids via amidoalkylation followed by hydrolysis
N-protected α-aminoDiprotic acids (phospho-isosteres of natural amino acids) via amidoalkylation reaction
Industrial uses:
This collector was developed recently and was used primarily as specific collector for cassiterite from ores with complex gangue composition.
On the basis of the Diprotic acid, Albright and Wilson had developed a range of collectors mainly for flotation of oxidic minerals (i.e. cassiterite, ilmenite and pyrochlore).
Very little is known about the performance of these collectors.
Limited studies conducted with cassiterite and rutile ores showed that some of these collectors produce voluminous froth but were very selective.
Properties of Diprotic acid:
Diprotic acid has a melting point of 70.1°C and is a colorless, tideless crystal; when heated to 200°C, Diprotic acid decomposes to form phosphine andphosphoric acid.
Diprotic acid is insoluble in water except for its alkali and calcium salts.
The acid dissociation constants of Diprotic acid are pKa = 1.5 and 6.79.
Chemical Properties:
Diprotic acid is a white crystalline deliquescent solid that can be prepared by the action of water on phosphorus( III) oxide or phosphorus(III) chloride.
Diprotic acid is a dibasic acid producing the anions H2PO3- and HPO3 2- in water.
Diprotic acid and its salts are slow reducing agents.
On warming, Diprotic acid decomposes to phosphine and phosphoric(V) acid.
Diprotic acid is used to prepare phosphite salts.
Diprotic acid is usually sold as a 20% aqueous solution.
Diprotic acid has strong reducing properties it tends to be converted to phosphoric acid.
On being heated dry Diprotic acid disproportionates to give phosphine and phosphoric acid.
H3PO3 + 3H3PO3 → PH3 + 3H3PO4
Diprotic acid reacts with a base like sodium hydroxide forms sodium phosphate and water.
H3PO3 + 3NaOH → Na3PO3 + 3H2O
Physical Properties:
Diprotic acid is a white crystalline mass.
Diprotic acid is deliquescent.
Diprotic acid is garlic-like odor.
Diprotic acid is density 1.651 g/cm3 at 21°C.
Diprotic acid is melts at 73.6°C.
Diprotic acid is decomposes at 200°C to phosphine and phosphoric acid.
Diprotic acid is soluble in water, about 310 g/100mL.
Diprotic acid is K1 5.1x10-2 and K2 1.8x10-7.
Diprotic acid is soluble in alcohol.
Redox Properties:
On heating at 200 °C, Diprotic acid disproportionates to phosphoric acid and phosphine:
4 H3PO3 → 3 H3PO4 + PH3
This reaction is used for laboratory-scale preparations of PH3.
Diprotic acid slowly oxidizes in air to phosphoric acid.
Both Diprotic acid and its deprotonated forms are good reducing agents, although not necessarily quick to react.
They are oxidized to phosphoric acid or its salts.
Diprotic acid reduces solutions of noble metal cations to the metals.
When Diprotic 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 Diprotic acid to mercury on heating or on standing:
H3PO3 + Hg2Cl2 + H2O → 2 Hg + H3PO4 + 2 HCl
Acid-base Properties:
Diprotic acid since the hydrogen bonded directly to the central phosphorus atom is not readily ionizable.
Chemistry examinations often test students' appreciation of the fact that all three hydrogen atoms are not acidic under aqueous conditions, in contrast with phosphoric acid.
HP(O)2(OH)− is a moderately strong acid.
HP(O)(OH)2 → HP(O)2(OH)− + H+ pKa = 1.3
HP(O)2(OH)− → HPO32− + H+ pKa = 6.7
The monodeprotonated species, HP(O)2(OH)− is called the phosphite ion.
The IUPAC (mostly organic) name is Diprotic acid.
This nomenclature of Diprotic acid is commonly reserved for substituted derivatives, that is, organic group bonded to phosphorus, not simply an ester.
For example, (CH3)PO(OH)2 is "methylDiprotic acid", which may of course form "methylphosphonate" esters.
Both Diprotic acid and its deprotonated forms are good reducing agents, although not necessarily quick to react.
They are oxidized to phosphoric acid or its salts.
Diprotic acid reduces solutions of noble metal cations to the metals.
Preparation of Diprotic acid:
Diprotic acid can be prepared by the reaction of phosphorus trichloride with water:
PCl3 + 3H2O → H3PO4 + 3HCl
The reaction is violent.
Addition of PCl3 should be extremely cautious and slow.
The addition can be carried out safely in the presence of concentrated HCl.
Alternatively, a stream of air containing PCl3 vapor is passed into icecold water and solid crystals of H3PO4 form.
Alternatively, Diprotic acid can be prepared by adding phosphorus trichloride to anhydrous oxalic acid:
PCl3 + 3(COOH）2 → H3PO3 + 3CO + 3CO2 + 3HCl
In this reaction, all products except Diprotic acid escape as gases leaving the liquid acid.
Dissolution of phosphorus sesquioxide in water also forms phosphorus acid.
When shaken with ice water, Diprotic acid is the only product.
P4O6 + 6H2O → 4H3PO3
However, in hot water part of the Diprotic acid disproportionates to phosphoric acid and phosphorus or phosphine.
Although commercially available, the acid is most commonly prepared by hydrolysis of phosphorus trichloride with water or steam:
PCl3 + 3 H2O → HP(O)(OH)2 + 3 HCl
Potassium phosphite is a convenient precursor to Diprotic acid:
K2HPO3 + 2 HCl → 2 KCl + H3PO3
In practice aqueous potassium phosphite is treated with excess hydrochloric acid.
By concentrating the solution and precipitations with alcohols, the pure acid can be separated from the salt.
On an industrial scale, Diprotic 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
Production of Diprotic acid:
The production of phosphoric acid is done via two main ways:
Wet process and thermal process.
The wet process involves the production of phosphoric acid from fluorapatite.
Diprotic acid is known as phosphate rock and the chemical composition is 3Ca3(PO4)2.CaF2.
This phosphate rock is finely ground to increase the surface area and is reacted with concentrated sulfuric acid that gives phosphoric acid and gypsum (CaSO4.2H2O) as products.
Ca5(PO4)3F + 5H2SO4 + 10H2O → 3H3PO4+ 5CaSO4·2H2O + HF
The thermal process of phosphoric acid production includes the burning elemental phosphorous to obtain very pure phosphoric acid.
The burning of elemental phosphorous gives phosphorous pentoxide (P2O5).
Diprotic acid is then hydrated to produce phosphoric acid.
P4 + 5O2→ 2P2O5
P2O5 + 3H2O → 2H3PO4
Major applications of phosphoric acid are in fertilizer production.
Phosphoric acid is used to produce three types of phosphorus fertilizers; triple superphosphate, diammonium hydrogen phosphate, and monoammonium dihydrogen phosphate.
Structure of Diprotic acid:
The differential formula of Diprotic acid is HP(=O)(OH )2, and the presence of the P-H bond is evident from physical measurements and the fact that only mono- and di-substituted salts are formed, and no trisubstituted salts are obtained.
The shape of the molecule is tetrahedral.
Diprotic acid is in tautomeric equilibrium with Diprotic acid.
The chemical formula for phosphite is P(OH) 3, and Diprotic acid is predominant in equilibrium.
In organophosphorus chemistry, Diprotic acid is a general term for organophosphorus compounds that have a phosphorus-hydrogen bond and a phosphoryl group.
Organic derivatives of Diprotic acid include alkyl Diprotic acid, in which the hydrogen atom on the phosphorus atom is replaced by an alkyl group, and alkyl Diprotic acid, in which the hydrogen atom on the hydroxy group is replaced by an alkyl group.
Alkyl Diprotic acid includes monoesters, in which only one alkyl group is substituted, and diesters, in which both alkyl groups are substituted.
Nomenclature And Tautomerism of Diprotic 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), Diprotic 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 the trihydroxy form P(OH)3 be called Diprotic acid, and the dihydroxy form HP(O)(OH)2 Diprotic 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)
Tautomerization:
Diprotic acid is better described with the structural formula HP(O)(OH)2.
This species exists in equilibrium with a minor tautomer P(OH)3.
The latter is called Diprotic acid.
Diprotic acid is sometimes called Diprotic acid or orthophosphorous acid.
Diprotic acid has been shown to be a stable tautomer.
The dihydroxy form, HP(O)(OH)2, is called Diprotic acid.
Many of the reduced phosphorus acids are subject to similarly complicated equilibria involving shifts of H between O and P.
In the solid state, HP(O)(OH)2 is tetrahedral with one shorter P=O bond of 148 pm and two longer P-O(H) bonds of 154 pm.
Polymerization of Diprotic acid:
An oligophosphorous acid of the Diprotic acid tautomer refers to a few molecules of Diprotic acid condensed into a molecule with the loss of water.
A general formula for such oligophosphorous acids is (HPO)nOn-1(OH)2, where n = 2, 3, 4, etc., oligo-.
A polyphosphorous acid can have dozens of such Diprotic acid units condensed in a row with the loss of H2O for each unit added on.
For the Diprotic acid tautomer, an oligophosphorous acid also refers to a few molecules condensed into a molecule with the loss of H2O as each unit of P(OH)3 is added on, but the general formula differs:
(HO)2PO[P(OH)O]n-2P(OH)2,
where n = 2, 3, 4, etc., oligo-.
Here for both tautomers the repeat unit is (HPO2)n-2.
Again, a polyphosphorous acid can have dozens of units condensed in a row.
Regardless of the value of n, both polyDiprotic acid and polyphosphorous acid have the same chemical formula for any specific n, e.g., triphosDiprotic acid is H5P3O7 and triphosphorous acid is H5P3O7 for n=3.
In oligophosphorous acids of sufficient size, there are multiple OH that can result in the condensation of a cyclophosphorous acid that does not have multiple (HPO3) metaphosphoric acid units.
However, the usual referral to a cyclophosphorous acid (cyclophosphonates or cyclophosphites) may be misnomers wherein the cyclic portion is carbon-based with a Diprotic acid side chain of one or more molecules, or one or a limited number of either of the two tautomers included in the ring but as a minority contributor.
For example the effect of varying ring size on the phosphonate-phosphite tautomerism of cyclophosphorous acids has been shown.
But the cyclophosphorous acids are biheteroorganic.
Branching can also occur in either oligophosphorous or polyphosphorous tautomer.
These are ultraoligophosphorous or ultrapolyphosphorous acids, ultraoligophosphonates and ultrapolyphosphonates, or ultraoligophosphites and ultrapolyphosphites, respectively for the phosphonic and phosphorous tautomers.
Reactions of Diprotic acid:
Acid–base properties:
Diprotic acid has a pKa in the range 1.26–1.3.
HP(O)(OH)2 → HP(O)2(OH)− + H+ pKa = 1.3
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.
As A Ligand, Diprotic acid:
Upon treatment with metals of d6 configuration, Diprotic 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 Diprotic acid gives the luminescent salt potassium diplatinum(II) tetrakispyrophosphite:
2 K2PtCl4 + 8 H3PO3 → K4[Pt2(HO2POPO2H)4] + 8 HCl + 4 H2O
Organic Derivatives of Diprotic acid:
The IUPAC (mostly organic) name is Diprotic acid.
This nomenclature of Diprotic acid is commonly reserved for substituted derivatives, that is, organic group bonded to phosphorus, not simply an ester.
For example, (CH3)PO(OH)2 is "methylDiprotic acid", which may of course form "methylphosphonate" esters.
Handling And Storage of Diprotic 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 Diprotic acid:
Reactivity:
Diprotic acid decomposes when heated to form phosphine, a gas that usually ignites spontaneously in air.
Absorbs oxygen from the air to form Diprotic acid.
Forms yellow deposits in aqueous solution that are spontaneously flammable upon drying.
Diprotic acid reacts exothermically with chemical bases (for example: amines and inorganic hydroxides) to form salts.
These reactions can generate dangerously large amounts of heat in small spaces.
Dissolution in water or dilution of a concentrated solution with additional water may generate significant heat.
Diprotic acid reacts in the presence of moisture with active metals, including such structural metals as aluminum and iron, to release hydrogen, a flammable gas.
Diprotic acid can initiate the polymerization of certain alkenes.
Diprotic acid reacts with cyanide compounds to release gaseous hydrogen cyanide.
Diprotic acid may generate flammable and/or toxic gases in contact with dithiocarbamates, isocyanates, mercaptans, nitrides, nitriles, sulfides, and strong reducing agents.
Additional gas-generating reactions occur with sulfites, nitrites, thiosulfates (to give H2S and SO3), dithionites (to give SO2), and carbonates (to give CO2).
Chemical stability:
Diprotic acid 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 Diprotic 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).
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 Diprotic acid:
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 Diprotic 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 Diprotic 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 Diprotic acid:
Appearance: white/light yellow liquid
Grade: Food Grade
Type: food additive
Molecular formula: H3PO4
HS code: 2809201900
CAS code: 7664-38-2
EINECS: 231-633-2 UN: 1805
Certificate: SGS/ISO certificate
Other names: orthophosphoric acid phosphoric(V) Acid
Molecular Weight: 81.99580
Exact Mass: 82.00
EC Number: 233-663-1
UNII: 95E079716M
UN Number: 2834
DSSTox ID: DTXSID7035511
HScode: 2811199090
PSA: 81.00000
XLogP3: -0.63930
Density: 1.651
Melting Point: 73 °C (approx)
Boiling Point: 200ºC
Flash Point: 200ºC
Water Solubility:
H2O: soluble
Storage Conditions: 0-6ºC
Air and Water Reactions: Deliquescent.
Properties of Diprotic 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
Structure:
Molecular shape: pseudo-tetrahedral
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: Diprotic acid has been shown not to be oxidizing
Other safety information: No data available
Molecular Weight: 81.996 g/mol
XLogP3-AA: -1.6
Hydrogen Bond Donor Count: 2
Hydrogen Bond Acceptor Count: 3
Rotatable Bond Count: 0
Exact Mass: 81.98198095 g/mol
Monoisotopic Mass: 81.98198095 g/mol
Topological Polar Surface Area: 57.5Ų
Heavy Atom Count: 4
Complexity: 26.3
Isotope Atom Count: 0
Defined Atom Stereocenter Count: 0
Undefined Atom Stereocenter Count: 0
Defined Bond Stereocenter Count: 0
Undefined Bond Stereocenter Count: 0
Covalently-Bonded Unit Count: 1
Compound Is Canonicalized: Yes
Absorbs oxygen from the air very readily to form phosphoric acid.
Soluble in water.
Reactive Group: Acids, Weak
Other Names: orthophosphoric acid; Anhydrous phosphoric acid
CAS No.: 7664-38-2
Molecular Formula/MF: H3PO4
EINECS No.: 231-633-2
Classification: Biochemical & chemical
Grade Standard: Food grade
Purity: 85% min
Odor: Odorless
Appearance: Colorless, transparent and syrupy liquid
H3PO3: Phosphorous Acid
Density: 1.65 g/cm³
Molecular Weight/ Molar Mass: 82 g/mol
Boiling Point: 200 °C
Melting Point: 73.6 °C
Chemical Formula: H3PO3
Odour: Sour odour
Appearance: White solid, deliquescent
Covalently-Bonded Unit: 1
Hydrogen Bond Acceptor: 3
Complexity: 8
Solubility: Soluble in water
Melting point: 73 °C
Boiling point: 200 °C
Density: 1.651 g/mL at 25 °C(lit.)
vapor pressure: 0.001Pa at 20℃
Flash point: 200°C
storage temp.: 0-6°C
solubility: DMSO (Slightly), Methanol (Slightly), Water (Sparingly)
form: Crystals
pka: pK1 1.29; pK2 6.74(at 25℃)
Specific Gravity: 1.651
color: White
Water Solubility: SOLUBLE
Sensitive: Air Sensitive & Hygroscopic
Merck: 14,7346
Stability: Stable.
Incompatible with strong bases.
Hygroscopic.
CAS DataBase Reference: 13598-36-2
EWG's Food Scores: 1
FDA UNII: 35V6A8JW8E
NIST Chemistry Reference: (HO)2HPO(13598-36-2)
EPA Substance Registry System: Diprotic acid (13598-36-2)
