Triethyl phosphate: Physicochemical properties and Uses

Physicochemical properties

Triethyl phosphate (TEP) is an organic compound with the chemical formula OP(OEt)3. It is a colourless, transparent liquid at room temperature with a subtle pleasant odour due to its ester portion. TEP has corrosive and flammable properties, and is soluble in water and other organic solvents such as ethanol and ether.

Uses of Triethyl phosphate

As a green solvent

Triethyl phosphate (TEP) is a new addition to the Green Solid Phase Peptide Synthesis (GSPPS) toolbox. TEP is virtually non-toxic and has no carcinogenic or mutagenic properties. Its degradation yields harmless phosphoric acid and ethanol.TEP's low viscosity makes it ideally suited for solid-phase peptide synthesis (SPPS), where solvent-delivered reagents should be able to penetrate the polymer matrix. TEP solubilises most Fmoc amino acids as well as key coupling reagents and additives. Several model peptides can be SPPS'd at room temperature with TEP using the most conventional polystyrene resins, whereas the use of other green solvents requires more complex resins and/or higher temperatures. In summary, TEP is a strong contender to become the green solvent of choice.

As a flame retardant

Triethyl phosphate can be used as a flame retardant electrolyte for sodium ion battery solvents. 1 M NaBF4 was added to the TEP with 3% vinyl carbonate used as a SEI forming additive. Using this electrolyte formulation, stable cycling performance was achieved with a capacity of 80.5 mA h g? after 200 cycles in a sodium-ion full cell of Na3.2V1.8Zn0.2(PO4)3 with hard carbon.

As production of flame retardant PIR foam

Phosphorus-containing flame retardants such as triethyl phosphate, oligotriethyl phosphate, diethyl phosphonate, diethyl hydroxymethylphosphonate, and ammonium polyphosphate were combined with the smoke suppressant zinc borate as additives for the production of non-toxic, smoke-suppressing, flame-retardant rigid polyurethane-polyisocyanurate (PIR) foams. The flame height and smoke density of polyurethane-polyisocyanurate foams were reduced by adding different combinations of combustion modifiers to the PIR formulation. The smoke inhibitor was zinc borate. The combination of zinc borate with triethyl phosphate, oligotriethyl phosphate and diethyl hydroxymethylphosphonate produced a good synergistic effect. Cone calorimeter analysis showed that the best combinations were zinc borate (10.1 per cent) and triethyl phosphate (13.7 per cent) or zinc borate (10.1 per cent), triethyl phosphate (6.9 per cent) and oligo-triethyl phosphate (7 per cent), which reduced the burning and smoking rates of PIR foams. These combinations can be used to produce flame retardant PIR foams in industry.

for the preparation of heat-resistant coatings of biological origin

It has been shown that wheat gluten protein hydrolysate SOLPRO 508 and casein react with triethyl phosphate (TEP) for the preparation of high temperature resistant coatings. The product coatings also have excellent adhesion and excellent solvent resistance. TEP has been shown to react with the following amino acid sites in casein (alanine, glutamine, proline, lysine, glycine, threonine, serine, and histidine) as well as in wheat gluten hydrolysates (tyrosine, alanine, glutamine, glycine, methionine, and threonine), resulting in protein cross-linking.

References:

[1] NANDHINI K P, CELE N, DE LA TORRE B G, et al. Triethyl phosphate (TEP) as a green solvent for solid-phase peptide synthesis (SPPS)[J]. Green Chemistry Letters and Reviews, 2024, 16 1. DOI:10.1080/17518253.2024.2330639.

[2] DU K, WANG C, BALAYA P, et al. A fire-retarding electrolyte using triethyl phosphate as a solvent for sodium-ion batteries†[J]. Chemical Communications, 2021. DOI:10.1039/D1CC04958E.

[3] S AMIROU; A P. Biosourced heat resistant coatings by cross-linking of proteins with triethyl phosphate[J]. Progress in Organic Coatings, 2020. DOI:10.1016/j.porgcoat.2019.105403.