Tripotassium phosphate

Chemical compound From Wikipedia, the free encyclopedia

Tripotassium phosphate, also called tribasic potassium phosphate[3] is a water-soluble salt with the chemical formula K3PO4.(H2O)x (x = 0, 3, 7, 9).[4] Tripotassium phosphate is basic: a 1% aqueous solution has a pH of 11.8.[4]

Quick facts Names, Identifiers ...
Tripotassium phosphate
Unit cell of the anhydrous tripotassium phosphate under standard conditions (low temperature modification).
Unit cell of tripotassium phosphate.
Names
IUPAC name
Potassium phosphate
Systematic IUPAC name
Potassium tetraoxidophosphate(3−)
Other names
Potassium phosphate, tribasic
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.029.006 Edit this at Wikidata
EC Number
  • 231-907-1
E number E340(iii) (antioxidants, ...)
UNII
  • InChI=1S/3K.H3O4P/c;;;1-5(2,3)4/h;;;(H3,1,2,3,4)/q3*+1;/p-3 checkY
    Key: LWIHDJKSTIGBAC-UHFFFAOYSA-K checkY
  • [K+].[K+].[K+].[O-]P([O-])([O-])=O
Properties
K3PO4
Molar mass 212.27 g/mol
Appearance White deliquescent powder
Density 2.564 g/cm3 (17 °C)
Melting point 1,380 °C (2,520 °F; 1,650 K)
90 g/100 mL (20 °C)
Solubility in ethanol Insoluble
Basicity (pKb) 1.6
Structure[1]
Primitive orthorhombic
Pnma, No. 62
a = 1.123772 nm, b = 0.810461 nm, c = 0.592271 nm[1]
Hazards[2]
Occupational safety and health (OHS/OSH):
Main hazards
 Irritant
GHS labelling:
GHS07: Exclamation mark
Warning
H319
P264, P280, P305+P351+P338, P337+P313
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
0
0
Flash point Non-flammable
Safety data sheet (SDS) MSDS
Related compounds
Other cations
 Trisodium phosphate
Triammonium phosphate
Tricalcium phosphate
Related compounds
 Monopotassium phosphate
Dipotassium phosphate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Production

Tripotassium phosphate is produced by the neutralization of phosphoric acid with potassium hydroxide:[4]

H3PO4 + 3KOH → K3PO4 + 3H2O

Use in organic chemistry

K3PO4

Tripotassium phosphate has few industrial applications, however it is commonly used as a base in laboratory-scale organic chemistry. Being insoluble in organic solvents, it is an easily removed proton acceptor in organic synthesis. The anhydrous salt is especially basic.[5] Some of the reactions are listed below:

  1. The hydrate (K3PO4·H2O) has been used to catalyze the deprotection of BOC amines. Microwave radiation is used to aid the reaction.[6]
  2. As a catalyst for the synthesis of unsymmetrical diaryl ethers using [Bmim]BF4 as the solvent. Aryl methane-sulfonates are deprotected and then followed by a nucleophilic aromatic substitution (SNAr) with activated aryl halides.[7]
  3. As a base in the cross-coupling reaction of aryl halides with terminal alkynes. It also plays a role in the deacetonation of 4-aryl-2-methylbut-3-yn-2-ol intermediates.[8]
  4. As the base in the cross-coupling reaction between aryl halides and phenols or aliphatic alcohols.[9]

Use in foods

Tripotassium phosphate can be used in foods as a buffering agent, emulsifying agent, and for nutrient fortification. It can serve as a sodium-free substitute for trisodium phosphate. The ingredient is most common in dry cereals but is also found in meat, sauces, and cheeses.[10]

References

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