Tetrakis(hydroxymethyl)phosphonium chloride

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Tetrakis(hydroxymethyl)phosphonium chloride
Other names	Tetrahydroxymethylphosphonium chloride, THPC
Identifiers
CAS number	[124-64-1]
Properties
Molecular formula	(HOCH2)4PCl
Molar mass	190.56 g/mol
Appearance	cyrstalline
Density	1.341 g/cm³
Melting point	150 °C (423 K)
Boiling point	N/A
Solubility in water	N/A
Hazards
R-phrases	R21 R25 R38 R41 R42/43 R51/53
S-phrases	S22 S26 S36/37/39 S45 S60 S61
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Tetrakis(hydroxymethyl)phosphonium chloride (THPC) is a phosphonium salt with the chemical formula [(CH2OH)4P]Cl . The cation (CH2OH)4P⁺ is a four-coordinate phosphorus compound with the phosphorus atom carrying a positive charge. THPC has industrial applications as precursors to fire-retardant materials and synthetic applications as precursor to the useful ligand, tris(hydroxymethyl)phosphine.

Contents 1 Synthesis and Uses of THPC 2 Tris(hydroxymethyl)phoshpine and Its Uses 3 Application in Textiles 4 References

[edit] Synthesis and Uses of THPC

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

PH₃ + 4 H₂C=O + HCl → [P(CH₂OH)₄]Cl

THPC is commonly used to prepare tris(hydroxymethyl)phoshpine by treating it with aqueous sodium hydroxide.^[1]

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

[edit] Tris(hydroxymethyl)phoshpine and Its Uses

Tris(hydroxymethyl)phosphine is an intermediate in the preparation of the water-soluble ligand 1,3,5-triaza-7-phosphaadamantane (PTA). This is done by treating hexamethylenetetramine with formaldehyde and tris(hydroxymethyl)phosphine.^[2] Tris(hydroxymethyl)phosphine can also be used to synthesize the heterocycle, N-boc-3-pyrroline by ring-closing metathesis using Grubb’s Catalyst. N-Boc-diallylamine is treated with the catalyst bis(tricyclohexylphosphine)benzylidineruthenium dichloride(Grubb’s Catalyst) followed by tris(hydroxymethyl)phosphine. The carbon-carbon double bonds undergo ring closure, releasing ethylene gas, resulting in N-boc-3-pyrroline.^[3] 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.^[4]

[edit] 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.^[5]

[P(CH₂OH)₄]Cl + NH₂CONH₂ → (CH₂OH)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.

[edit] References

1. ^ 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. ^ Daigel, Donald J. 1,3,5-triaza-7phosphatricyclo[3.3.1.13.7]decane and derivatives, Inorganic Synthesis. Vol. 32, p.40-42 (1998). DOI: 10.1002/9780470132630.ch6
3. ^ Ferguson, Marcelle L.; O’Leary, Daniel J.; Grubbs, Robert H. Ring-Closing Metathesis Synthesis Of N-Boc-3-Pyrroline. Organic Syntheses. Annual Vol. 80, p.85 (2003)
4. ^ Vullo, W. J. Hydroxymethyl Replacement Reactions of Tetrakis(hydroxymethyl)phosphonium Chloride. Ind. Eng. Chem. Prod. Res. Dev. 1966. 58(4); 346-349. (No DOI)
5. ^ Reeves, Wilson A.; Guthrie, John D. Intermediate for Flame-Resistant Polymers-Reactions of Tetrakis(hydroxymethyl)phosphonium Chloride. Industrial Engineering Chemistry. 1956. 48(1); 64-67. DOI: 10.1021/ie50553a021