Tripotassium phosphate

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.

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
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 diamond
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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Infobox references

Production

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

Use in organic chemistry
K3PO4

Tripotassium phosphate has few industrial applications.

It is used as an inert, easily removed proton acceptor in organic synthesis. Some of the reactions are listed below:

  1. The hydrate () has been used to catalyze the deprotection of BOC amines. Microwave radiation is used to aid the reaction.[5]
  2. As a catalyst for the synthesis of unsymmetrical diaryl ethers using [Bmim] as the solvent. Aryl methane-sulfonates are deprotected and then followed by a nucleophilic aromatic substitution (SNAr) with activated aryl halides.[6]
  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.[7]
  4. As the base in the cross-coupling reaction between aryl halides and phenols or aliphatic alcohols.[8]

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.[9]

Hazards

It is somewhat basic: a 1% aqueous solution has a pH of 11.8.[4]

References
  1. Voronin, V. I.; Ponosov, Yu. S.; Berger, I. F.; Proskurnina, N. V.; Zubkov, V. G.; Tyutyunnik, A. P.; Bushmeleva, S. N.; Balagurov, A. M.; Sheptyakov, D. V.; Burmakin, E. I.; Shekhtman, G. Sh.; Vovkotrub, E. G. (2006). "Crystal structure of the low-temperature form of K3PO4". Inorganic Materials. 42 (8): 908–913. doi:10.1134/S0020168506080206. S2CID 92351896.
  2. "Potassium phosphate". pubchem.ncbi.nlm.nih.gov.
  3. "Potassium phosphate tribasic P5629". Sigma-Aldrich. Retrieved 2018-04-27.
  4. Klaus Schrödter; Gerhard Bettermann; Thomas Staffel; Friedrich Wahl; Thomas Klein; Thomas Hofmann (2012). "Phosphoric Acid and Phosphates". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a19_465.pub3.
  5. Dandepally, Srinivasa Reddy; Williams, Alfred L. (2009-03-04). "Microwave-assisted N-Boc deprotection under mild basic conditions using K3PO4·H2O in MeOH". Tetrahedron Letters. 50 (9): 1071–1074. doi:10.1016/j.tetlet.2008.12.074. ISSN 0040-4039.
  6. Xu, Hui; Chen, Yang (2007-04-30). "C(aryl)-O Bond Formation from Aryl Methanesulfonates via Consecutive Deprotection and SNAr Reactions with Aryl Halides in an Ionic Liquid". Molecules. 12 (4): 861–867. doi:10.3390/12040861. PMC 6149384. PMID 17851438.
  7. Shirakawa, Eiji; Kitabata, Takaaki; Otsuka, Hidehito; Tsuchimoto, Teruhisa (2005-10-10). "A simple catalyst system for the palladium-catalyzed coupling of aryl halides with terminal alkynes". Tetrahedron. 61 (41): 9878–9885. doi:10.1016/j.tet.2005.07.099. ISSN 0040-4020.
  8. Niu, Jiajia; Zhou, Hua; Li, Zhigang; Xu, Jingwei; Hu, Shaojing (2008-10-03). "An Efficient Ullmann-Type C−O Bond Formation Catalyzed by an Air-Stable Copper(I)−Bipyridyl Complex". The Journal of Organic Chemistry. 73 (19): 7814–7817. doi:10.1021/jo801002c. ISSN 0022-3263. PMID 18771324.
  9. Han, James (2020-08-03). "What is Tripotassium Phosphate E340(iii) in Food and Functions in Cereals?". foodadditives.net. Retrieved 2022-12-22.
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