|Molar mass||190.56 g/mol|
150 °C (423 K)
|Solubility in water||N/A|
|R-phrases||R21 R25 R38 R41 R42/43 R51/53|
|S-phrases||S22 S26 S36/37/39 S45 S60 S61|
| (what is: / ?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Tetrakis(hydroxymethyl)phosphonium chloride (THPC) is an organophosphorus compound with the chemical formula [P(CH2OH)4]Cl. The cation P(CH2OH)4+ is four-coordinate, as is typical for phosphonium salts. THPC has applications as a precursor to fire-retardant materials.
Synthesis and reactions 
- PH3 + 4 H2C=O + HCl → [P(CH2OH)4]Cl
- [P(CH2OH)4]Cl + NaOH → P(CH2OH)3 + H2O + H2C=O + NaCl
Application in textiles 
THPC has industrial importance in the production of crease-resistant and flame-retardant finishes on cotton textiles and other cellulosic fabrics. A flame-retardant finish can be prepared from THPC by the Proban Process, in which THPC is treated with urea. The urea condenses with the hydroxymethyl groups on THPC. The phosphonium structure is converted to phosphine oxide as the result of this reaction.
- [P(CH2OH)4]Cl + NH2CONH2 → (HOCH2)2POCH2NHCONH2 + HCl + HCHO + H2 + H2O
This reaction proceeds rapidly, forming insoluble high molecular weight polymers. The resulting product is applied to the fabrics in a "pad-dry process." This treated material is then treated with ammonia and ammonia hydroxide to produce fibers that are flame-retardant.
THPC can condense with many other types of monomers in addition to urea. These monomers include amines, phenols, and polybasic acids and anhydrides.
Tris(hydroxymethyl)phosphine and its uses 
Tris(hydroxymethyl)phosphine, which is derived from tetrakis(hydroxymethyl)phosphonium chloride, is an intermediate in the preparation of the water-soluble ligand 1,3,5-triaza-7-phosphaadamantane (PTA). This conversion is achieved by treating hexamethylenetetramine with formaldehyde and tris(hydroxymethyl)phosphine.
Tris(hydroxymethyl)phosphine can also be used to synthesize the heterocycle, N-boc-3-pyrroline by ring-closing metathesis using Grubbs' catalyst (bis(tricyclohexylphosphine)benzylidineruthenium dichloride ). N-Boc-diallylamine is treated with Grubbs' catalyst, followed by tris(hydroxymethyl)phosphine. The carbon-carbon double bonds undergo ring closure, releasing ethylene gas, resulting in N-boc-3-pyrroline. The hydroxymethyl groups on THPC undergo replacement reactions when THPC is treated with α,β-unsaturated nitrile, acid, amide, and epoxides. For example, base induces condensation between THPC and acrylamide with displacement of the hydroxymethyl groups. (Z = CONH2)
- [P(CH2OH)4]Cl + NaOH + 3CH2=CHZ → P(CH2CH2Z)3 + 4CH2O + H2O + NaCl
- Svara, Jürgen; Weferling, Norbert ; Hofmann, Thomas. Phosphorus Compounds, Organic. Ullmann's Encyclopedia of Industrial Chemistry. John Wiley & Sons, Inc, 2008 doi:10.1002/14356007.a19_545.pub2
- M. Caporali, L. Gonsalvi, F. Zanobini, M. Peruzzini "Synthesis of the Water-Soluble Bidentate (P,N) Ligand PTN(Me)" Inorg. Syntheses, 2011, Vol. 35, p. 92–108. doi:10.1002/9780470651568.ch5
- Weil, Edward D. ; Levchik, Sergei V. (2008). "Flame Retardants in Commercial Use or Development for Textiles". J. Fire Sci. 26 (3): 243–281. doi:10.1177/0734904108089485.
- "Frequently asked questions: What is the PROBAN® process?". Rhodia Proban. Retrieved February 25, 2013.
- Reeves, Wilson A.; Guthrie, John D. (1956). "Intermediate for Flame-Resistant Polymers-Reactions of Tetrakis(hydroxymethyl)phosphonium Chloride". Industrial Engineering Chemistry 48 (1): 64–67. doi:10.1021/ie50553a021.
- Daigel, Donald J.; Decuir, Tara J.; Robertson, Jeffrey B.; Darensbourg, Donald J. (1998). "1,3,5-triaza-7phosphatricyclo[126.96.36.199.7]decane and derivatives". Inorg. Synth. Inorganic Syntheses 32: 40–42. doi:10.1002/9780470132630.ch6. ISBN 978-0-470-13263-0.
- Ferguson, Marcelle L.; O’Leary, Daniel J.; Grubbs, Robert H. (2003), "Ring-Closing Metathesis Synthesis Of N-Boc-3-Pyrroline", Org. Synth. 80: 85
- Vullo, W. J. (1966). "Hydroxymethyl Replacement Reactions of Tetrakis(hydroxymethyl)phosphonium Chloride". Ind. Eng. Chem. Prod. Res. Dev. 58 (4): 346–349. doi:10.1021/i360020a011.