tetrakis(hydroxymethyl)phosphonium chloride
{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 408885713
| Name = Tetrakis(hydroxymethyl){{SHY}}phosphonium chloride
| ImageFile = Tetrakis(hydroxymethyl)phosphonium chloride.png
| PIN = Tetrakis(hydroxymethyl)phosphonium chloride
| OtherNames = Tetrahydroxymethylphosphonium chloride, THPC
| Section1 = {{Chembox Identifiers
| CASNo_Ref = {{cascite|correct|??}}
| CASNo = 124-64-1
| ChEMBL = 2131547
| EC_number = 204-707-7
| RTECS = TA2450000
| UNNumber = 2810
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 58WB2XCF8I
| ChemSpiderID =29038
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| PubChem = 31298
}}
| Section2 = {{Chembox Properties
| C=4|H=12|Cl=1|O=4|P=1
| Appearance = white solid
| Density = 1.341 g/cm3
| MeltingPtC = 150
}}
| Section7 = {{Chembox Hazards
| ExternalSDS =
| GHSPictograms = {{GHS05}}{{GHS06}}{{GHS07}}{{GHS08}}{{GHS09}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|301|302|311|312|314|315|330|334|411}}
| PPhrases = {{P-phrases|260|261|264|270|271|273|280|284|285|301+310|301+312|301+330+331|302+352|303+361+353|304+340|304+341|305+351+338|310|312|320|321|322|330|332+313|342+311|361|362|363|391|403+233|405|501}}
}}
}}
Tetrakis(hydroxymethyl)phosphonium chloride (THPC) is an organophosphorus compound with the chemical formula [P(CH2OH)4]Cl. It is a white water-soluble salt with applications as a precursor to fire-retardant materials{{Ullmann|doi=10.1002/14356007.a19_545.pub2|title=Phosphorus Compounds, Organic|year=2006|last1=Svara|first1=Jürgen|last2=Weferling|first2=Norbert|last3=Hofmann|first3=Thomas|isbn=3527306730}} and as a microbiocide in commercial and industrial water systems.
Synthesis, structure and reactions
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
The cation P(CH2OH)4+ features four-coordinate phosphorus, as is typical for phosphonium salts.
THPC converts to tris(hydroxymethyl)phosphine upon treatment with aqueous sodium hydroxide: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}}
:[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.{{cite book|doi=10.1002/14356007.a26_227 |chapter=Textile Auxiliaries |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2000 |last1=Fischer |first1=Klaus |last2=Marquardt |first2=Kurt |last3=Schlüter |first3=Kaspar |last4=Gebert |first4=Karlheinz |last5=Borschel |first5=Eva-Marie |last6=Heimann |first6=Sigismund |last7=Kromm |first7=Erich |last8=Giesen |first8=Volker |last9=Schneider |first9=Reinhard |last10=Lee Wayland |first10=Rosser |isbn=3-527-30673-0 }}
{{cite journal |author1=Weil, Edward D. |author2=Levchik, Sergei V. | title = Flame Retardants in Commercial Use or Development for Textiles | journal = J. Fire Sci. | year = 2008 | volume = 26 | issue = 3 | pages = 243–281 | doi = 10.1177/0734904108089485|s2cid=98355305 }} A flame-retardant finish can be prepared from THPC by the Proban Process,{{cite web|url=http://www.rhodia-proban.com/uk/faq.asp|title=Frequently asked questions: What is the PROBAN® process?|publisher=Rhodia Proban|access-date=February 25, 2013|archive-date=December 7, 2012|archive-url=https://web.archive.org/web/20121207081548/http://www.rhodia-proban.com/uk/faq.asp|url-status=dead}} 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.{{cite journal |author1=Reeves, Wilson A. |author2=Guthrie, John D. | title = Intermediate for Flame-Resistant Polymers-Reactions of Tetrakis(hydroxymethyl)phosphonium Chloride | journal = Industrial and Engineering Chemistry | year = 1956 | volume = 48 | issue = 1 | pages = 64–67 | doi = 10.1021/ie50553a021}}
:[P(CH2OH)4]Cl + NH2CONH2 → (HOCH2)2P(O)CH2NHC(O)NH2 + 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.