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Encyclopedia > Phosphorus pentachloride
Phosphorus pentachloride
General
Systematic name Phosphorus(V) chloride
Other names Pentachlorophosphorus
Molecular formula PCl5
SMILES ClP(Cl)(Cl)(Cl)Cl
Molar mass 208.22 g mol−1
Appearance colorless crystals
CAS number [10026-13-8]
Properties
Density and phase 1.6 g cm−3
Solubility in water decomposition (violent)
Other solvents carbon disulfide,
chlorocarbons,
benzene
Melting point 179–181 °C
Boiling point sublimation 70-80 °C
(vacuum)
Structure
Coordination
geometry
trigonal bipyramidal
Crystal structure
Dipole moment 0 D
Hazards
MSDS External MSDS
Main hazards HCl source
NFPA 704
R/S statement R: 14-22-26-34-48/20
S: 26-36/37/39-45-7/8
RTECS number TB6125000
Supplementary data page
Structure and
properties
n, εr, etc.
Thermodynamic
data
Phase behaviour
Solid, liquid, gas
Spectral data Raman:
456 cm−1 (PCl4+)
354 cm−1 (PCl6)
393 cm-1 (PCl5)
Related compounds
Related compounds POCl3,
PCl3,
PF5
Except where noted otherwise, data are given for
materials in their standard state (at 25 °C, 100 kPa)
Infobox disclaimer and references

Gaseous and molten PCl5 is a neutral molecule with trigonal bipyramidal (D3h) symmetry. The structure of “PCl5” in solution, however, depends on the solvent and on the concentration.[1] In polar solvents, dilute solutions dissociate according to the following equilibrium: The symmetry group of an object (e. ... A solvent is a fluid phase (liquid, gas, or plasma) that dissolves a solid, liquid, or gaseous solute, resulting in a solution. ...

PCl5 $overrightarrow{leftarrow}$ [PCl4+]Cl

At higher concentrations, a second equilibrium becomes more important:

2 PCl5 $overrightarrow{leftarrow}$ [PCl4+][PCl6]

The cation PCl4+ and the anion PCl6 are tetrahedral and octahedral, respectively. The structures for the phosphorus chlorides are invariably consistent with VSEPR theory. Geometry of the water molecule Molecules have fixed equilibrium geometries--bond lengths and angles--that are dictated by the laws of quantum mechanics. ...

In non-polar solvents, such as CS2 and CCl4, the D3h structure seen in gaseous and liquid remains intact.[2] Carbon disulfide (CS2) is a colorless liquid with a pleasant odor that is like the smell of chloroform. ... R-phrases , , , , S-phrases , , , , , Flash point non flammable RTECS number FG4900000 Supplementary data page Structure and properties n, Îµr, etc. ...

At one time, PCl5 in solution was thought to form a dimeric structure, P2Cl10, but this suggestion is not supported by the Raman spectroscopic measurements. Raman spectroscopy is a spectroscopic technique used in condensed matter physics and chemistry to study vibrational, rotational, and other low-frequency modes in a system. ...

## Preparation

PCl5 is prepared by the chlorination of PCl3. This reaction was used to produce ca. 10,000,000 kg of PCl5 in 2000.[3] Chlorination is the process of adding the element chlorine to water as a method of water purification to make it fit for human consumption as drinking water. ...

PCl3 + Cl2 $overrightarrow{leftarrow}$ PCl5 ΔH = −124 kJ/mol

PCl5 exists in equilibrium with PCl3 and chlorine, at 180 °C, the degree of dissociation is ca. 40%.[3] Because of this equilibrium, samples of PCl5 are often contains chlorine, which imparts a greenish coloration. General Name, Symbol, Number chlorine, Cl, 17 Chemical series halogens Group, Period, Block 17, 3, p Appearance yellowish green Atomic mass 35. ...

## Hydrolysis

In its most characteristic reaction, PCl5 react upon contact with water to release hydrogen chloride and give phosphorus oxides. The first hydrolysis product is phosphorus oxychloride A chemical reaction occurs when vapours of hydrogen chloride and ammonia meet to form a cloud of a new substance, ammonium chloride Chemical reaction is a process that results in the interconversion of chemical substances [1]. The substance or substances initially involved in a chemical reaction are called reactants. ... This article describes water from a scientific and technical perspective. ... R-phrases , S-phrases , , , , Flash point non-flammable Supplementary data page Structure and properties n, Îµr, etc. ... Phosphorus trichloride Phosphorus pentachloride (gas phase structure) Phosphorus oxychloride[1] Phosphorus trichloride (PCl3) and phosphorus pentachloride (PCl5) are reactive chemicals used as chlorinating reagents in a chemical laboratory. ...

PCl5 + H2O → POCl3 + 2 HCl

In hot water, hydrolysis proceeds completely to ortho-phosphoric acid: Phosphoric acid, also known as orthophosphoric acid or phosphoric(V) acid, is an inorganic mineral acid having the chemical formula H3PO4. ...

PCl5 + 4 H2O → H3PO4 + 5 HCl

## Other reactions

Most often PCl5 is used for chlorinations.[4]

### Chlorinations of organic compounds with PCl5

In synthetic chemistry, two classes of chlorination are usually of interest. Oxidative chlorinations entail the transfer of Cl2 from the reagent to the substrate. Substitutive chlorinations entail replacement of O or OH groups with chloride. PCl5 can be used for both processes.

PCl5 will convert carboxylic acids to the corresponding acyl chloride[5] as well as alcohols to alkyl chloride. Thionyl chloride is more commonly used in the laboratory because the SO2 is more easily separated from the organic products than is POCl3. Structure of a carboxylic acid The 3D structure of the carboxyl group A space-filling model of the carboxyl group Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the formula -(C=O)-OH, usually written as -COOH. In general, the salts and anions... General Chemical Structure of an Acyl Chloride In organic chemistry, an acyl chloride (or acid chloride) is an organic compound which is a reactive derivative of a carboxylic acid. ... Functional group of an alcohol molecule. ... In chemistry, an alkyl halide is an organic molecule of the form R_X, where X is a halide and R contains a carbon atom bonded to other functional groups or hydrogens. ... R-phrases , , , S-phrases , , , Flash point non flammable Supplementary data page Structure and properties n, Îµr, etc. ...

PCl5/PCl3 bears some resemblance to SO2Cl2, as both serve often as sources of Cl2. Again for oxidative chlorinations on the laboratory scale, SO2Cl2 is often preferred over PCl5 since the gaseous SO2 by-product is readily separated. Sulfuryl chloride is SO2Cl2, a compound composed of sulfur, oxygen, and chlorine. ... Sulfuryl chloride is SO2Cl2, a compound composed of sulfur, oxygen, and chlorine. ...

PCl5 reacts with a tertiary amides, such as DMF, to give dimethylchloromethyleneammonium chloride, which is called the Vilsmeier reagent, [(CH3)2NCClH]Cl. More typically, a related salt is generated from the reaction of DMF and POCl3. Such reagents are useful in the preparation of derivatives of benzaldehyde by formylation and for the conversion of C-OH groups into C-Cl groups.[4] Dimethylformamide, also known under the names N,N-dimethylformamide and DMF, is a clear, water-miscible liquid and common solvent that is often used in chemical reactions. ... The Vilsmeier-Haack reaction or Vilsmeier reaction is an organic reaction between a substituted amide and a activated arene in the presence of phosphorus oxychloride. ... The chemical compound benzaldehyde (C6H5CHO) consists of a benzene ring with an aldehyde group attached to one carbon. ...

In contrast to PCl3, the pentachloride replaces allylic and benzylic CH bonds and is especially renown for the conversion of C=O groups to CCl2 groups.[6]

The electrophilic character of PCl5 is highlighted by its reaction with styrene to give, after hydrolysis, phosphonic acid derivatives.[7] In chemistry, an electrophile (literally electron-lover) is a reagent attracted to electrons that participates in a chemical reaction by accepting an electron pair in order to bond to a substance. ... C8H8 redirects here. ... Hydrolysis is a chemical reaction or process in which a molecule is split into two parts by reacting with a molecule of water, which has the chemical formula H2O. One of the parts gets an OH- from the water molecule and the other part gets an H+ from the water. ...

### Chlorination of inorganic compounds

As for the reactions with organic compounds, the use of PCl5 has been superseded by SO2Cl2. The reaction of phosphorus pentoxide and PCl5 produces POCl3:[2]: Phosphorus pentoxide, perhaps more accurately diphosphorus pentoxide, is so called because of its empirical formula P2O5, as should be expected of any element in oxidation number +5. ... Phosphorus trichloride Phosphorus pentachloride (gas phase structure) Phosphorus oxychloride[1] Phosphorus trichloride (PCl3) and phosphorus pentachloride (PCl5) are reactive chemicals used as chlorinating reagents in a chemical laboratory. ...

6 PCl5 + P4O10 → 10 POCl3

PCl5 chlorinates nitrogen dioxide: [1] R-phrases , S-phrases , , , , , Supplementary data page Structure and properties n, Îµr, etc. ...

PCl5 + 2 NO2 → PCl3 + 2 NO2Cl

PCl5 is a precursor for lithium hexafluorophosphate, LiPF6, an electrolytes in lithium ion battery: The nitronium ion, NO2+, is not stable enough to exist in normal conditions, but it is used extensively in the nitration of other substances. ... Hexafluorophosphate is an anion with chemical formula of [PF6]-. It is a good leaving group. ... An electrolyte is a substance which dissociates free ions when dissolved (or molten), to produce an electrically conductive medium. ... Lithium ion batteries (sometimes abbreviated Li-Ion) are a type of rechargeable battery commonly used in consumer electronics. ...

PCl5 + 6 LiF → LiPF6 + 5 LiCl

Lithium fluoride, or LiF, is a compound of lithium and fluoride, white and a crystalline solid in appearance. ... Lithium chloride behaves as a fairly typical ionic compound, although the Li+ ion is very small. ...

## Safety

PCl5 is a dangerous substance as it reacts violently with water and is a source of both hydrogen chloride and chlorine. R-phrases , S-phrases , , , , Flash point non-flammable Supplementary data page Structure and properties n, Îµr, etc. ... General Name, Symbol, Number chlorine, Cl, 17 Chemical series halogens Group, Period, Block 17, 3, p Appearance yellowish green Atomic mass 35. ...

There are three series of binary phosphorus halides, containing phosphorus in the oxidation states +5, +3 and +2. ...

## References

1. ^ Suter, R. W.; Knachel, H. C.; Petro, V. P.; Howatson, J. H.; S. G. Shore, S. G. ”Nature of Phosphorus(V) Chloride in Ionizing and Nonionizing Solvents” Journal of the American Chemical Society 1973, volume 95, pp 1474 - 1479; DOI: 10.1021/ja00786a021
2. ^ D. E. C. Corbridge "Phosphorus: An Outline of its Chemistry, Biochemistry, and Technology" 5th Edition Elsevier: Amsterdam 1995. ISBN 0-444-89307-5.
3. ^ a b Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
4. ^ a b Burks, Jr., J. E. “Phosphorus(V) Chloride” in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. DOI: 10.1002/047084289.
5. ^ Adams, R.; Jenkins, R. L. “p-Nitrobenzoyl chloride” Organic Syntheses, Collected Volume 1, p.394 (1941).
6. ^ Gross, H.; Rieche, A.; Höft, E.; Beyer, E. “Dichloromethyl Methyl Ether” Organic Syntheses, Collected Volume 5, p.365 (1973).
7. ^ Schmutzler, R. ”Styrylphosphonic dichloride” Organic Syntheses, Collected Voume 5, p.1005 (1973).

Roger Adams (1889â€“1971) was an American organic chemist. ...

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