Tripotassium phosphate explained

Tripotassium phosphate, also called tribasic potassium phosphate[1] is a water-soluble salt with the chemical formula K3PO4.(H2O)x (x = 0, 3, 7, 9). Tripotassium phosphate is basic.

Production

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

Use in organic chemistry

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.[2] 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.[3]
  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.[4]
  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.[5]
  4. As the base in the cross-coupling reaction between aryl halides and phenols or aliphatic alcohols.[6]

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.[7]

Hazards

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

Notes and References

  1. Web site: Potassium phosphate tribasic P5629. Sigma-Aldrich. 2018-04-27.
  2. Book: 10.1002/047084289X.rn01172 . Potassium Phosphate . Encyclopedia of Reagents for Organic Synthesis . 2010 . Chiong . Hendrich A. . 978-0-471-93623-7 .
  3. 2009-03-04. Microwave-assisted N-Boc deprotection under mild basic conditions using K3PO4·H2O in MeOH. Tetrahedron Letters. en. 50. 9. 1071–1074. 10.1016/j.tetlet.2008.12.074. 0040-4039. Dandepally. Srinivasa Reddy. Williams. Alfred L..
  4. 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. en. 12. 4. 861–867. 10.3390/12040861. 17851438. 6149384. free.
  5. 2005-10-10. A simple catalyst system for the palladium-catalyzed coupling of aryl halides with terminal alkynes. Tetrahedron. en. 61. 41. 9878–9885. 10.1016/j.tet.2005.07.099. 0040-4020. Shirakawa. Eiji. Kitabata. Takaaki. Otsuka. Hidehito. Tsuchimoto. Teruhisa.
  6. 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. EN. 73. 19. 7814–7817. 10.1021/jo801002c. 18771324. 0022-3263.
  7. Web site: Han . James . 2020-08-03 . What is Tripotassium Phosphate E340(iii) in Food and Functions in Cereals? . 2022-12-22 . foodadditives.net . en-US.

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