Selenium trioxide

Selenium trioxide[1] | Structural formula of the monomer as found in the gas phase | Space-filling model of the monomer as found in the gas phase

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Identifiers

CAS Number

* 13768-86-0 N

3D model (JSmol)

* monomer: Interactive image
* cyclic tetramer: Interactive image

ChemSpider |

* 103019 Y

PubChem CID

* 115128

InChI

* InChI=1S/O3Se/c1-4(2)3 Y

Key: VFLXBUJKRRJAKY-UHFFFAOYSA-N Y

* InChI=1/O3Se/c1-4(2)3

Key: VFLXBUJKRRJAKY-UHFFFAOYAC

SMILES

* monomer: O=[Se](=O)=O

* cyclic tetramer: O=[Se]0(=O)O[Se](=O)(=O)O[Se](=O)(=O)O[Se](=O)(=O)O0

Properties

Chemical formula

| SeO3
Molar mass | 126.96 g/mol
Appearance  | white hygroscopic crystals
Density | 3.44 g/cm3
Melting point |  118.35 °C (245.03 °F; 391.50 K)
Boiling point | sublimes

Solubility in water

| very soluble
Structure

Crystal structure

| tetragonal
Hazards
GHS pictograms |
GHS Signal word | Danger

GHS hazard statements

| H301, H331, H373, H410
NFPA 704 (fire diamond)  |

Lethal dose or concentration (LD, LC):

LD50 (median dose)

| 7 mg/kg (rat, oral)
7.08 mg/kg (mouse, oral)
5.06 mg/kg (guinea pig, oral)
2.25 mg/kg (rabbit, oral)
13 mg/kg (horse, oral)[2]

LC50 (median concentration)

| 13 mg/kg (pig, oral)
9.9 mg/kg (cow, oral)
3.3 mg/kg (goat, oral)
3.3 mg/kg (sheep, oral)[2]

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

N verify (what is YN ?)
Infobox references

Selenium trioxide is the inorganic compound with the formula SeO3. It is white, hygroscopic solid. It is also an oxidizing agent and a Lewis acid. It is of academic interest as a precursor to Se(VI) compounds.[4]

## Contents

* 1 Preparation
* 2 Reactions
* 3 Structure
* 4 References
* 5 Further reading

## Preparation

Selenium trioxide is difficult to prepare because it is unstable with respect to the dioxide:

2 SeO3 → 2 SeO2 \+ O2

It has been generated in a number of ways despite the fact that the dioxide does not combust under normal conditions.[4] One method entails dehydration of anhydrous selenic acid with phosphorus pentoxide at 150–160 °C. Another method is the reaction of liquid sulfur trioxide with potassium selenate.

SO3 \+ K2SeO4 → K2SO4 \+ SeO3

## Reactions

In its chemistry SeO3 generally resembles sulfur trioxide, SO3, rather than tellurium trioxide, TeO3.[4] The substance reacts explosively with oxidizable organic compounds.[5]

At 120 °C SeO3 reacts with selenium dioxide to form the Se(VI)-Se(IV) compound diselenium pentaoxide:[6]

SeO3 \+ SeO2 → Se2O5

It reacts with selenium tetrafluoride to form selenoyl fluoride, the selenium analogue of sulfuryl fluoride

2SeO3 \+ SeF4 → 2SeO2F2 \+ SeO2

As with SO3 adducts are formed with Lewis bases such as pyridine, dioxane and ether.[4]

With lithium oxide and sodium oxide it reacts to form salts of SeVIO54− and SeVIO66−:[7] With Li2O, it gives Li4SeO5, containing the trigonal pyramidal anion SeVIO54− with equatorial bonds, 170.6–171.9 pm; and longer axial Se−O bonds of 179.5 pm. With Na2O it gives Na4SeO5, containing the square pyramidal SeVIO54−, with Se−O bond lengths ranging from range 172.9 → 181.5 pm, and Na12(SeO4)3(SeO6), containing octahedral SeVIO66−. SeVIO66− is the conjugate base of the unknown orthoselenic acid (Se(OH)6).

## Structure

In the solid phase SeO3 consists of cyclic tetramers, with an 8 membered (Se−O)4 ring. Selenium atoms are 4-coordinate, bond lengths being Se−O bridging are 175 pm and 181 pm, non-bridging 156 and 154 pm.[7]

SeO3 in the gas phase consists of tetramers and monomeric SeO3 which is trigonal planar with an Se−O bond length of 168.78 pm.[8]

## References

1. ↑ Lide, David R. (1998). Handbook of Chemistry and Physics (87 ed.). Boca Raton, Florida: CRC Press. pp. 4–81. ISBN 0-8493-0594-2.
2. ↑ 2.0 2.1 "Selenium compounds (as Se)". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH). https://www.cdc.gov/niosh/idlh/7782492.html.
3. ↑ "C&L Inventory". https://echa.europa.eu/information-on-chemicals/cl-inventory-database/-/discli/details/153441.
4. ↑ 4.0 4.1 4.2 4.3 Egon Wiberg, Arnold Frederick Holleman (2001) Inorganic Chemistry, Elsevier ISBN 0123526515
5. ↑ Schmidt, Bornmann & Wilhelm 1963.
6. ↑ Z. Žák "Crystal structure of diselenium pentoxide Se2O5" Zeitschrift für anorganische und allgemeine Chemie 1980, volume 460, pp. 81–85. doi:10.1002/zaac.19804600108
7. ↑ 7.0 7.1 Handbook of Chalcogen Chemistry: New Perspectives in Sulfur, Selenium and Tellurium, Franceso A. Devillanova, Royal Society of Chemistry, 2007, ISBN 9780854043668
8. ↑ Brassington, N. J.; Edwards, H. G. M.; Long, D. A.; Skinner, M. (1978). "The pure rotational Raman spectrum of SeO3". Journal of Raman Spectroscopy 7 (3): 158–160. doi:10.1002/jrs.1250070310. ISSN 0377-0486. Bibcode: 1978JRSp....7..158B.

## Further reading

* Schmidt, Prof. Dr. Max; Bornmann, Dr. P.; Wilhelm, Dr. Irmgard (1963-10-02). "The Chemistry of Selenium Trioxide". Angewandte Chemie International Edition in English 2 (11): 691–692. doi:10.1002/anie.196306913.

* v
* t
* e

Selenium compounds

Se(−II)|

* Ag2Se
* Al2Se3
* CaSe
* Se2−

Se(0,I)|

* Se3S5

Se(I)|

* Se2S6
* Se2Cl2
* C3H7NO2Se

Se(II)|

* SeS2

Se(IV)|

* SeCl4
* SeF4
* SeO2
* SeS2
* SeOBr2
* SeOCl2

Se(VI)|

* SeF6
* SeO3
* SeO2F2

* v
* t
* e

Oxides

Mixed oxidation states|

* Antimony tetroxide (Sb2O4)
* Cobalt(II,III) oxide (Co3O4)
* Europium(II,III) oxide (Eu3O4)
* Iron(II,III) oxide (Fe<sub>3O4)
* Lead(II,IV) oxide (Pb3O4)
* Manganese(II,III) oxide (Mn3O4)
* Silver(I,III) oxide (Ag2O2)
* Triuranium octoxide (U3O8)
* Carbon suboxide (C3O2)
* Mellitic anhydride (C12O9)
* [[Chemistry:Praseodymium(III,IV) Praseodymium(III,IV) oxide]] (Pr6O11)
* Terbium(III,IV) oxide (Tb4O7)

+1 oxidation state|

* Copper(I) oxide (Cu<sub>2O)
* Caesium oxide (Cs2O)
* Dicarbon monoxide (C2O)
* Dichlorine monoxide (Cl2O)
* Gallium(I) oxide (Ga2O)
* Lithium oxide (Li2O)
* Potassium oxide (K2O)
* Rubidium oxide (Rb2O)
* Silver oxide (Ag2O)
* Thallium(I) oxide (Tl2O)
* Sodium oxide (Na2O)
* Water (hydrogen oxide) (H2O)

+2 oxidation state|

* Aluminium(II) oxide (AlO)
* Barium oxide (BaO)
* Beryllium oxide (BeO)
* Cadmium oxide (CdO)
* Calcium oxide (CaO)
* Carbon monoxide (CO)
* Chromium(II) oxide (CrO)
* Cobalt(II) oxide (CoO)
* Copper(II) oxide (CuO)
* Europium(II) oxide (EuO)
* Germanium monoxide (GeO))
* Iron(II) oxide (FeO)
* Lead(II) oxide (PbO)
* Magnesium oxide (MgO)
* Manganese(II) oxide (MnO)
* Mercury(II) oxide (HgO)
* Nickel(II) oxide (NiO)
* Nitric oxide (NO)
* Palladium(II) oxide (PdO)
* Silicon monoxide (SiO)
* Strontium oxide (SrO)
* Sulfur monoxide (SO)
* Disulfur dioxide (S2O2)
* Thorium monoxide (ThO)
* Tin(II) oxide (SnO)
* Titanium(II) oxide (TiO)
* Vanadium(II) oxide (VO)
* Zinc oxide (ZnO)

+3 oxidation state|

* Aluminium oxide (Al<sub>2O3)
* Antimony trioxide (Sb2O3)
* Arsenic trioxide (As2O3)
* Bismuth(III) oxide (Bi2O3)
* Boron trioxide (B2O3)
* Cerium(III) oxide (Ce2O3)
* Dibromine trioxide (Br2O3)
* Chromium(III) oxide (Cr2O3)
* Dinitrogen trioxide (N2O3)
* Dysprosium(III) oxide (Dy2O3)
* Erbium(III) oxide (Er2O3)
* Europium(III) oxide (Eu2O3)
* Gadolinium(III) oxide (Gd2O3)
* Gallium(III) oxide (Ga2O3)
* Holmium(III) oxide (Ho2O3)
* Indium(III) oxide (In<sub>2O3)
* Iron(III) oxide (Fe2O3)
* Lanthanum oxide (La2O3)
* Lutetium(III) oxide (Lu2O3)
* Manganese(III) oxide (Mn2O3)
* Neodymium(III) oxide (Nd2O3)
* Nickel(III) oxide (Ni2O3)
* Phosphorus trioxide (P4O6)
* Praseodymium(III) oxide (Pr2O3)
* Promethium(III) oxide (Pm2O3)
* Rhodium(III) oxide (Rh2O3)
* [[Chemistry:Samarium(III) Samarium(III) oxide]] (Sm2O3)
* Scandium oxide (Sc2O3)
* Terbium(III) oxide (Tb2O3)
* Thallium(III) oxide (Tl2O3)
* Thulium(III) oxide (Tm2O3)
* Titanium(III) oxide (Ti2O3)
* Tungsten(III) oxide (W2O3)
* Vanadium(III) oxide (V2O3)
* Ytterbium(III) oxide (Yb2O3)
* Yttrium(III) oxide (Y2O3)

+4 oxidation state|

* Americium dioxide (AmO2)
* Carbon dioxide (CO2)
* Carbon trioxide (CO3)
* Cerium(IV) oxide (CeO2)
* Chlorine dioxide (ClO2)
* Chromium(IV) oxide (CrO<sub>2)
* Dinitrogen tetroxide (N2O4)
* Germanium dioxide (GeO<sub>2)
* [[Chemistry:Hafnium(IV) Hafnium(IV) oxide]] (HfO2)
* Lead dioxide (PbO2)
* Manganese dioxide (MnO2)
* Neptunium(IV) oxide (NpO2)
* Nitrogen dioxide (NO2)
* Osmium dioxide (OsO2)
* Plutonium(IV) oxide (PuO2)
* Praseodymium(IV) oxide (PrO2)
* Protactinium(IV) oxide (PaO2)
* Rhodium(IV) oxide (RhO2)
* Ruthenium(IV) oxide (RuO<sub>2)
* Selenium dioxide (SeO2)
* Silicon dioxide (SiO2)
* Sulfur dioxide (SO2)
* Tellurium dioxide (TeO<sub>2)
* [[Chemistry:Terbium(IV) Terbium(IV) oxide]] (TbO2)
* Thorium dioxide (ThO2)
* Tin dioxide (SnO2)
* Titanium dioxide (TiO<sub>2)
* Tungsten(IV) oxide (WO2)
* Uranium dioxide (UO2)
* Vanadium(IV) oxide (VO2)
* Zirconium dioxide (ZrO2)

+5 oxidation state|

* Antimony pentoxide (Sb2O5)
* Arsenic pentoxide (As2O5)
* Dinitrogen pentoxide (N2O5)
* Niobium pentoxide (Nb2O5)
* Phosphorus pentoxide (P2O5)
* Protactinium(V) oxide (Pa2O5)
* Tantalum pentoxide (Ta2O5)
* Vanadium(V) oxide (V2O5)

+6 oxidation state|

* Chromium trioxide (CrO3)
* Molybdenum trioxide (MoO3)
* Rhenium trioxide (ReO3)
* Selenium trioxide (SeO3)
* Sulfur trioxide (SO3)
* Tellurium trioxide (TeO3)
* Tungsten trioxide (WO3)
* Uranium trioxide (UO3)
* Xenon trioxide (XeO3)
* Iridium trioxide (IrO3)

+7 oxidation state|

* Dichlorine heptoxide (Cl2O7)
* Manganese heptoxide (Mn2O7)
* [[Chemistry:Rhenium(VII) Rhenium(VII) oxide]] (Re2O7)
* Technetium(VII) oxide (Tc2O7)

+8 oxidation state|

* Osmium tetroxide (OsO4)
* Ruthenium tetroxide (RuO4)
* Xenon tetroxide (XeO4)
* Iridium tetroxide (IrO4)
* Hassium tetroxide (HsO4)

Related|

* Oxocarbon
* Suboxide
* Oxyanion
* Ozonide
* Peroxide
* Superoxide

Oxides are sorted by oxidation state. Category:Oxides

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*[CID]: Compound ID
*[H301]: Toxic if swallowed
*[H331]: Toxic if inhaled
*[H373]: May cause damage to organs through prolonged or repeated exposure
*[H410]: Very toxic to aquatic life with long lasting effects
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