Tripotassium phosphate

Tripotassium phosphate, also called tribasic potassium phosphate is a water-soluble salt with the chemical formula K₃PO₄^._x. Tripotassium phosphate is basic: a 1% aqueous solution has a pH of 11.8.

Production

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

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. Some of the reactions are listed below:

The hydrate has been used to catalyze the deprotection of BOC amines. Microwave radiation is used to aid the reaction.
As a catalyst for the synthesis of unsymmetrical diaryl ethers using BF₄ as the solvent. Aryl methane-sulfonates are deprotected and then followed by a nucleophilic aromatic substitution with activated aryl halides.
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.
As the base in the cross-coupling reaction between aryl halides and phenols or aliphatic alcohols.

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.