Tetrakis(hydroxymethyl)phosphonium chloride

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Tetrakis(hydroxymethyl)phosphonium chloride
Tetrakis(hydroxymethyl)phosphonium chloride.png
Other names
Tetrahydroxymethylphosphonium chloride, THPC
ECHA InfoCard 100.004.280
Molar mass 190.56 g·mol−1
Appearance cyrstalline
Density 1.341 g/cm3
Melting point 150 °C (302 °F; 423 K)
Boiling point N/A
R-phrases (outdated) R21 R25 R38 R41 R42/43 R51/53
S-phrases (outdated) S22 S26 S36/37/39 S45 S60 S61
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

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,[1] as well as a microbicide in commercial and industrial water systems.

Synthesis and reactions[edit]

THPC can be synthesized with high yield by treating phosphine with formaldehyde in the presence of hydrochloric acid.[1]

PH3 + 4 H2C=O + HCl → [P(CH2OH)4]Cl

THPC is commonly used to prepare tris(hydroxymethyl)phosphine by treating it with aqueous sodium hydroxide.[2]

[P(CH2OH)4]Cl + NaOH → P(CH2OH)3 + H2O + H2C=O + NaCl

Application in textiles[edit]

THPC has industrial importance in the production of crease-resistant and flame-retardant finishes on cotton textiles and other cellulosic fabrics.[3] A flame-retardant finish can be prepared from THPC by the Proban Process,[4] 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.[5]

[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[edit]

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.[6]

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.[7] 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

Similar reactions occur when THPC is treated with acrylic acid; only one hydroxymethyl group is displaced, however.[8]


  1. ^ a b 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
  2. ^ 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
  3. ^ 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.
  4. ^ "Frequently asked questions: What is the PROBAN® process?". Rhodia Proban. Retrieved February 25, 2013.
  5. ^ Reeves, Wilson A.; Guthrie, John D. (1956). "Intermediate for Flame-Resistant Polymers-Reactions of Tetrakis(hydroxymethyl)phosphonium Chloride". Industrial and Engineering Chemistry. 48 (1): 64–67. doi:10.1021/ie50553a021.
  6. ^ Daigel, Donald J.; Decuir, Tara J.; Robertson, Jeffrey B.; Darensbourg, Donald J. (1998). "1,3,5-triaza-7phosphatricyclo[]decane and derivatives". Inorg. Synth. Inorganic Syntheses. 32: 40–42. doi:10.1002/9780470132630.ch6. ISBN 978-0-470-13263-0.
  7. ^ Ferguson, Marcelle L.; O’Leary, Daniel J.; Grubbs, Robert H. (2003). "Ring-Closing Metathesis Synthesis Of N-Boc-3-Pyrroline". Organic Syntheses. 80: 85.
  8. ^ 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.