Telluric acid, or more accurately orthotelluric acid, is a chemical compound with the formula Te(OH)6, often written as H6TeO6. It is a white crystalline solid made up of octahedral Te(OH)6 molecules which persist in aqueous solution.[2] In the solid state, there are two forms, rhombohedral and monoclinic, and both contain octahedral Te(OH)6 molecules,[3] containing one hexavalent tellurium (Te) atom in the +6 oxidation state, attached to six hydroxyl (–OH) groups, thus, it can be called tellurium(VI) hydroxide.
Telluric acid is a weak acid which is dibasic, forming tellurate salts with strong bases and hydrogen tellurate salts with weaker bases or upon hydrolysis of tellurates in water.[3][4] It is used as tellurium-source in the synthesis of oxidation catalysts.
Quick Facts Names, Identifiers ...
Telluric acid
|
|
Names |
IUPAC name
Hexahydroxidotellurium |
Other names
- Orthotelluric acid
- Hexahydroxytellurium
- Hexahydroxy-λ6-tellane
- Tellurium hexahydroxide
- Tellurium(VI) hydroxide
|
Identifiers |
|
|
|
|
ChEBI |
|
ChemSpider |
|
ECHA InfoCard |
100.029.334 |
|
|
UNII |
|
|
|
InChI=1S/H2O4Te/c1-5(2,3)4/h(H2,1,2,3,4) YKey: XHGGEBRKUWZHEK-UHFFFAOYSA-N YInChI=1/H2O4Te/c1-5(2,3)4/h(H2,1,2,3,4) Key: XHGGEBRKUWZHEK-UHFFFAOYAT
|
|
Properties |
|
Te(OH)6 |
Molar mass |
229.64 g·mol−1 |
Appearance |
White monoclinic crystals |
Density |
3.07 g/cm3 |
Melting point |
136 °C (277 °F; 409 K) |
|
50.1 g/(100 ml) at 30 °C[1] |
Acidity (pKa) |
7.68, 11.0 at 18 °C[1] |
Conjugate base |
Tellurate |
Structure |
|
octahedral |
|
0 D |
Hazards |
Occupational safety and health (OHS/OSH): |
Main hazards |
corrosive |
Related compounds |
|
Hydrotelluric acid Tellurous acid Hydrogen telluride |
Related compounds |
Teflic acid Sulfuric acid Selenic acid |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|
Close
The anhydrous acid is stable in air at 100 °C but above this it dehydrates to form polymetatelluric acid, a white hygroscopic powder (approximate composition (H2TeO4)10), and allotelluric acid, an acid syrup of unknown structure (approximate composition 3·H2TeO4·4H2O).[5][2]
Typical salts of the acid contains the anions [Te(O)(OH)5]− and [Te(O)2(OH)4]2−. The presence of the tellurate ion TeO2−4 has been confirmed in the solid state structure of Rb6[TeO5][TeO4].[6]
Strong heating at over 300 °C produces the α crystalline modification of tellurium trioxide, α-TeO3.
[4] Reaction with diazomethane gives the hexamethyl ester, Te(OCH3)6.[2]
Telluric acid and its salts mostly contain hexacoordinate tellurium.[3] This is true even for salts such as magnesium tellurate, MgTeO4, which is isostructural with magnesium molybdate and contains TeO6 octahedra.[3]
Metatelluric acid, H2TeO4, the tellurium analogue of sulfuric acid, H2SO4, is unknown. Allotelluric acid of approximate composition 3·H2TeO4·4H2O, is not well characterised and may be a mixture of Te(OH)6 and (H2TeO4)n.[2]
Lide, David R. (1998), Handbook of Chemistry and Physics (87 ed.), Boca Raton, Florida: CRC Press, ISBN 0-8493-0594-2 Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5. Catherine E. Housecroft; Alan G. Sharpe (2008). "Chapter 16: The group 16 elements". Inorganic Chemistry, 3rd Edition. Pearson. p. 526. ISBN 978-0-13-175553-6.