Tetrakis(hydroxymethyl)phosphonium chloride
Encyclopedia
Tetrakisphosphonium 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.
in the presence of hydrochloric acid
.
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)
Similar reactions occur when THPC is treated with acrylic acid
; only one hydroxymethyl group is displaced, however.
condenses with the hydroxymethyl groups on THPC. The phosphonium structure is converted to phosphine oxide
as the result of this reaction.
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.
Phosphonium salt
A phosphonium salt is a salt containing the phosphonium ion such as phosphonium iodide . More commonly, phosphonium refers to a quaternary organic derivative such as tetraphenylphosphonium chloride, 4P+ Cl- and tetramethylphosphonium iodide, [P4]+I−.Alkyltriphenylphosphonium salts are widely...
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.
Synthesis
THPC can be synthesized with high yield by treating phosphine with formaldehydeFormaldehyde
Formaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...
in the presence of hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
.
- PH3 + 4 H2C=O + HCl → [P(CH2OH)4]Cl
Reactions
THPC is commonly used to prepare tris(hydroxymethyl)phosphine by treating it with aqueous sodium hydroxide.- [P(CH2OH)4]Cl + NaOH → P(CH2OH)3 + H2O + H2C=O + NaCl
Tris(hydroxymethyl)phosphine 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.Tris(hydroxymethyl)phosphine can also be used to synthesize the heterocycle, N-boc-3-pyrroline by ring-closing metathesis using Grubbs' catalyst
Grubbs' catalyst
Grubbs' Catalyst is a transition metal carbene complex named after Robert H. Grubbs, the chemist who first synthesized it. There are two generations of the catalyst, as shown on the right. In contrast to other olefin metathesis catalysts, Grubbs' Catalysts tolerate other functional groups in the...
(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
Similar reactions occur when THPC is treated with acrylic acid
Acrylic acid
Acrylic acid is an organic compound with the formula CH2=CHCO2H. It is the simplest unsaturated carboxylic acid, consisting of a vinyl group connected directly to a carboxylic acid terminus. This colorless liquid has a characteristic acrid or tart smell. It is miscible with water, alcohols,...
; only one hydroxymethyl group is displaced, however.
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 ureaUrea
Urea or carbamide is an organic compound with the chemical formula CO2. The molecule has two —NH2 groups joined by a carbonyl functional group....
condenses with the hydroxymethyl groups on THPC. The phosphonium structure is converted to phosphine oxide
Phosphine oxide
Phosphine oxides are either inorganic phosphorus compounds such as phosphoryl trichloride or organophosphorus compounds with the formula OPR3, where R = alkyl or aryl...
as the result of this reaction.
- [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.