 | |||
| |||
 | |||
| Names | |||
|---|---|---|---|
| Preferred IUPAC name Phosphoryl trichloride[1] | |||
Other names
| |||
| Identifiers | |||
3D model (JSmol) | |||
| ChEBI | |||
| ChemSpider |
| ||
| ECHA InfoCard | 100.030.030 | ||
| EC Number |
| ||
| 2272 | |||
| RTECS number |
| ||
| UNII | |||
| UN number | 1810 | ||
| |||
| |||
| Properties | |||
| POCl3 | |||
| Molar mass | 153.32 g·mol−1 | ||
| Appearance | colourless liquid, fumes in moist air | ||
| Odor | pungent and musty | ||
| Density | 1.645 g/cm3, liquid | ||
| Melting point | 1.25 °C (34.25 °F; 274.40 K) | ||
| Boiling point | 105.8 °C (222.4 °F; 378.9 K) | ||
| Reacts | |||
| Solubility | highly soluble inbenzene,chloroform,carbon disulfide,carbon tetrachloride | ||
| Vapor pressure | 40 mmHg (27 °C)[2] | ||
Refractive index (nD) | 1.460 | ||
| Structure | |||
| Tetrahedral at theP atom | |||
| 2.54D | |||
| Thermochemistry[3] | |||
| 138.8 J·mol−1·K−1 (liquid), 84.9 J·mol−1·K−1 (gas) | |||
Std molar entropy(S⦵298) | 222.5 J·mol−1·K−1 (liquid), 325.5 J·mol−1·K−1 (gas) | ||
Std enthalpy of formation(ΔfH⦵298) | −597.1 kJ·mol−1 (liquid), −558.5 kJ·mol−1 (gas) | ||
Gibbs free energy(ΔfG⦵) | −520.8 kJ·mol−1 (liquid), −512.9 kJ·mol−1(gas) | ||
Enthalpy of fusion(ΔfH⦵fus) | 13.1 kJ·mol−1 | ||
Enthalpy of vaporization(ΔfHvap) | 38.6 kJ·mol−1 | ||
| Hazards | |||
| Occupational safety and health (OHS/OSH): | |||
Main hazards | Toxic andcorrosive; releasesHCl on contact withwater[2] | ||
| GHS labelling: | |||
    | |||
| Danger | |||
| H302,H314,H330,H372 | |||
| P260,P264,P270,P271,P280,P284,P301+P312,P301+P330+P331,P303+P361+P353,P304+P340,P305+P351+P338,P310,P314,P320,P321,P330,P363,P403+P233,P405,P501 | |||
| NFPA 704 (fire diamond) | |||
| Lethal dose or concentration (LD, LC): | |||
LD50 (median dose) | 380 mg/kg (rat, oral) | ||
| NIOSH (US health exposure limits): | |||
PEL (Permissible) | none[2] | ||
REL (Recommended) | TWA 0.1 ppm (0.6 mg/m3) ST 0.5 ppm (3 mg/m3)[2] | ||
IDLH (Immediate danger) | N.D.[2] | ||
| Safety data sheet (SDS) | ICSC 0190 | ||
| Related compounds | |||
Related compounds | |||
| Supplementary data page | |||
| Phosphoryl chloride (data page) | |||
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |||
Phosphoryl chloride (commonly calledphosphorus oxychloride) is a colourless liquid with the formulaPOCl3. It hydrolyses in moist air releasingphosphoric acid and fumes ofhydrogen chloride. It is manufactured industrially on a large scale fromphosphorus trichloride andoxygen orphosphorus pentoxide.[4] It is mainly used to makephosphate esters.
Like phosphate,POCl3 is tetrahedral in shape.[6] It features three P−Cl bonds and one strong P–O bond, with an estimatedbond dissociation energy of 533.5 kJ/mol. Unlike in the case ofPOF3, the Schomaker-Stevenson rule predicts appropriate bond length for the P–O bond only if the P–O bond is treated as a double bond, P=O.[citation needed] More modern treatments explain the tight P–O bond as a combination of lone pair transfer from the phosphorus to the oxygen atom and adativeπ back-bond that produces an effective [P+]-[O−] configuration.[7]
Phosphoryl chloride exists as neutralPOCl3 molecules in thesolid, liquid and gas states. This is unlikephosphorus pentachloride which exists as neutralPCl5 molecules in the gas and liquid states but adopts theionic form[PCl4]+[PCl6]− (tetrachlorophosphonium hexachlorophosphate(V)) in the solid state. The average bond lengths in thecrystal structure ofPOCl3 are 1.98 Å for P–Cl and 1.46 Å for P=O.[5]
It has acritical pressure of 3.4atm.[8] With a freezing point of 1 °C and boiling point of 106 °C, the liquid range ofPOCl3 is rather similar to water. Also like water,POCl3autoionizes, owing to the reversible formation of[POCl2]+cations (dichlorooxophosphonium cations) andCl−anions.
POCl3 reacts with water to givehydrogen chloride andphosphoric acid:
Intermediates in the conversion have been isolated, includingpyrophosphoryl chloride,O(−P(=O)Cl2)2.[9]
Upon treatment with excessalcohols andphenols,POCl3 givesphosphate esters:
Such reactions are often performed in the presence of an HCl acceptor such aspyridine or anamine.
POCl3 can also act as aLewis base, formingadducts with a variety ofLewis acids such astitanium tetrachloride:
Thealuminium chloride adduct (POCl3·AlCl3) is quite stable, and soPOCl3 can be used to removeAlCl3 from reaction mixtures, for example at the end of aFriedel-Crafts reaction.
POCl3 reacts withhydrogen bromide in the presence of Lewis-acidic catalysts to producePOBr3.
Phosphoryl chloride can be prepared by many methods. Phosphoryl chloride was first reported in 1847 by the French chemistAdolphe Wurtz by reactingphosphorus pentachloride with water.[10]
The commercial method involves oxidation ofphosphorus trichloride withoxygen:[11]
An alternative method involves the oxidation of phosphorus trichloride withpotassium chlorate:[12]
The reaction ofphosphorus pentachloride (PCl5) withphosphorus pentoxide (P4O10).
The reaction can be simplified bychlorinating a mixture ofPCl3 andP4O10, generating thePCl5in situ.The reaction ofphosphorus pentachloride withboric acid oroxalic acid:[12]
Reduction oftricalcium phosphate with carbon in the presence ofchlorine gas:[13]
The reaction of phosphorus pentoxide withsodium chloride is also reported:[13]
Phosphoryl chloride is used on an industrial scale for the manufacture ofphosphate esters (organophosphates). These have a wide range of uses, including asflame retardants (bisphenol A diphenyl phosphate,TCPP andtricresyl phosphate),plasticisers forPVC and related polymers (2-ethylhexyl diphenyl phosphate) and hydraulic fluids.[11] POCl3 is also used in the production of organophosphate insecticides.
In the semiconductor industry,POCl3 is used as a safe liquid phosphorus source in diffusion processes. The phosphorus acts as a dopant used to createn-type layers on a silicon wafer.
In the laboratory,POCl3 is a reagent in dehydrations. One example involves conversion of formamides to isonitriles (isocyanides);[14] primaryamides tonitriles:[15]
In a related reaction, certain aryl-substituted amides can be cyclized using theBischler-Napieralski reaction.
Such reactions are believed to proceed via animidoyl chloride. In certain cases, the imidoyl chloride is the final product. For example,pyridones andpyrimidones can be converted to chloro- derivatives such as2-chloropyridines and 2-chloropyrimidines, which are intermediates in the pharmaceutical industry.[16]
In theVilsmeier-Haack reaction,POCl3 reacts withamides to produce a "Vilsmeier reagent", a chloro-iminium salt, which subsequently reacts with electron-rich aromatic compounds to produce aromatic aldehydes upon aqueous work-up.[17]
{{cite book}}: CS1 maint: location missing publisher (link) CS1 maint: others (link)